Faculty Publications: December, 2016

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Title:
BICEP2/Keck Array VIII: Measurement of Gravitational Lensing from Large-scale B-mode Polarization
Authors:
BICEP2 Collaboration; Keck Array Collaboration; Ade, P. A. R.; Ahmed, Z.;... Dvorkin, C.;... Kovac, J. M.;... and 58 coauthors.
Publication:
The Astrophysical Journal, Volume 833, Issue 2, article id. 228, 12 pp. (2016). (ApJ Homepage)
Publication Date:
12/2016
Origin:
IOP
Astronomy Keywords:
cosmic background radiation, cosmology: observations, gravitational lensing: weak, polarization
DOI:
10.3847/1538-4357/833/2/228
Bibliographic Code:
2016ApJ...833..228B

Abstract

We present measurements of polarization lensing using the 150 GHz maps, which include all data taken by the BICEP2 and Keck Array Cosmic Microwave Background polarization experiments up to and including the 2014 observing season (BK14). Despite their modest angular resolution (˜0.5°), the excellent sensitivity (˜3μK-arcmin) of these maps makes it possible to directly reconstruct the lensing potential using only information at larger angular scales ({ℓ}≤700). From the auto-spectrum of the reconstructed potential, we measure an amplitude of the spectrum to be ALφ φ=1.15+/- 0.36 (Planck ΛCDM prediction corresponds to ALφ φ =1) and reject the no-lensing hypothesis at 5.8σ, which is the highest significance achieved to date using an EB lensing estimator. Taking the cross-spectrum of the reconstructed potential with the Planck 2015 lensing map yields ALφ φ =1.13+/- 0.20. These direct measurements of ALφ φ are consistent with the ΛCDM cosmology and with that derived from the previously reported BK14 B-mode auto-spectrum (AL{BB}=1.20+/-0.17). We perform a series of null tests and consistency checks to show that these results are robust against systematics and are insensitive to analysis choices. These results unambiguously demonstrate that the B modes previously reported by BICEP/Keck at intermediate angular scales(150≲ ℓ ≲ 350) are dominated by gravitational lensing. The good agreement between the lensing amplitudes obtained from the lensing reconstruction and B-mode spectrum starts to place constraints on any alternative cosmological sources of B modes at these angular scales.

 

Title:
Sensitivity and resolution in frequency comb spectroscopy of buffer gas cooled polyatomic molecules
Authors:
Changala, P. Bryan; Spaun, Ben; Patterson, David; Doyle, John M.; Ye, Jun
Publication:
Applied Physics B, Volume 122, Issue 12, article id.292, 11 pp. (ApPhB Homepage)
Publication Date:
12/2016
Origin:
SPRINGER
Abstract Copyright:
(c) 2016: Springer-Verlag Berlin Heidelberg
DOI:
10.1007/s00340-016-6569-7
Bibliographic Code:
2016ApPhB.122..292C

Abstract

We discuss the use of cavity-enhanced direct frequency comb spectroscopy in the mid-infrared region with buffer gas cooling of polyatomic molecules for high-precision rovibrational absorption spectroscopy. A frequency comb coupled to an optical enhancement cavity allows us to collect high-resolution, broad-bandwidth infrared spectra of translationally and rotationally cold (10-20 K) gas-phase molecules with high absorption sensitivity and fast acquisition times. The design and performance of the combined apparatus are discussed in detail. Recorded rovibrational spectra in the CH stretching region of several organic molecules, including vinyl bromide (CH_2CHBr), adamantane (C_{10}H_{16}), and diamantane (C_{14}H_{20}) demonstrate the resolution and sensitivity of this technique, as well as the intrinsic challenges faced in extending the frontier of high-resolution spectroscopy to large complex molecules.

 

Title:
Thermoelectric transport in disordered metals without quasiparticles: the SYK models and holography
Authors:
Davison, Richard A.; Fu, Wenbo; Georges, Antoine; Gu, Yingfei; Jensen, Kristan; Sachdev, Subir
Publication:
eprint arXiv:1612.00849
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons, High Energy Physics - Theory
Comment:
57 pages, 6 figures
Bibliographic Code:
2016arXiv161200849D

Abstract

We compute the thermodynamic properties of the Sachdev-Ye-Kitaev (SYK) models of fermions with a conserved fermion number, $\mathcal{Q}$. We extend a previously proposed Schwarzian effective action to include a phase field, and this describes the low temperature energy and $\mathcal{Q}$ fluctuations. We obtain higher-dimensional generalizations of the SYK models which display disordered metallic states without quasiparticle excitations, and we deduce their thermoelectric transport coefficients. We also examine the corresponding properties of Einstein-Maxwell-scalar theories on black brane geometries which interpolate from either AdS$_4$ or AdS$_5$ to an AdS$_2\times \mathbb{R}^2$ or AdS$_2\times \mathbb{R}^3$ near-horizon geometry. These provide holographic descriptions of non-quasiparticle metallic states without momentum conservation. We find a precise match between low temperature transport and thermodynamics of the SYK and holographic models. In both models the Seebeck transport coefficient is exactly equal to the $\mathcal{Q}$-derivative of the entropy. For the SYK models, quantum chaos, as characterized by the butterfly velocity and the Lyapunov rate, universally determines the thermal diffusivity, but not the charge diffusivity.

 

Title:
Deep learning in color: towards automated quark/gluon jet discrimination
Authors:
Komiske, Patrick T.; Metodiev, Eric M.; Schwartz, Matthew D.
Publication:
eprint arXiv:1612.01551
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
High Energy Physics - Phenomenology, Statistics - Machine Learning
Comment:
23 pages, 9 figures
Bibliographic Code:
2016arXiv161201551K

Abstract

Artificial intelligence offers the potential to automate challenging data-processing tasks in collider physics. To establish its prospects, we explore to what extent deep learning with convolutional neural networks can discriminate quark and gluon jets better than observables designed by physicists. Our approach builds upon the paradigm that a jet can be treated as an image, with intensity given by the local calorimeter deposits. We supplement this construction by adding color to the images, with red, green and blue intensities given by the transverse momentum in charged particles, transverse momentum in neutral particles, and pixel-level charged particle counts. Overall, the deep networks match or outperform traditional jet variables. We also find that, while various simulations produce different quark and gluon jets, the neural networks are surprisingly insensitive to these differences, similar to traditional observables. This suggests that the networks can extract robust physical information from imperfect simulations.

 

Title:
Topological frequency conversion in strongly driven quantum systems
Authors:
Martin, Ivar; Refael, Gil; Halperin, Bertrand
Publication:
eprint arXiv:1612.02143
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Mesoscale and Nanoscale Physics, Quantum Physics
Comment:
17 pages
Bibliographic Code:
2016arXiv161202143M

Abstract

When a physical system is subjected to a strong external multi-frequency drive, its dynamics can be conveniently represented in the multi-dimensional Floquet lattice. The number of the Floquet lattice dimensions equals the number of {\em irrationally}-related drive frequencies, and the evolution occurs in response to a built-in effective "electric" field, whose components are proportional to the corresponding drive frequencies. The mapping allows to engineer and study temporal analogs of many real-space phenomena. Here we focus on the specific example of a two-level system under two-frequency drive that induces topologically nontrivial band structure in the 2D Floquet space. The observable consequence of such construction is quantized pumping of energy between the sources with frequencies $\omega_1$ and $\omega_2$. When the system is initialized into a Floquet band with the Chern number $C$, the pumping occurs at the rate $P_{12} = -P_{21}= (C/2\pi)\hbar \omega_1\omega_2$, an exact counterpart of the transverse current in a conventional topological insulator.

 

Title:
A novel regime for the dynamical Casimir effect
Authors:
Ordaz-Mendoza, B. E.; Yelin, S. F.
Publication:
eprint arXiv:1612.02525
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Quantum Physics
Comment:
5 pages + Supplementary Material
Bibliographic Code:
2016arXiv161202525O

Abstract

The dynamical Casimir effect (DCE) is the production of photons by the amplification of vacuum fluctuations. In this paper we demonstrate new resonance conditions in DCE that potentially allow the production of optical photons when the mechanical frequency is smaller than the lowest frequency of the cavity field. We consider a cavity with one mirror fixed and the other allowed to oscillate. In order to identify the region where production of photons takes place, we do a linear stability analysis and investigate the dynamic stability of the system under small fluctuations. By using a numerical solution of the Heisenberg equations of motion, the time evolution of the number of photons produced in the unstable region is studied.

 

Title:
Mapping the Extinction Curve in 3D: Structure on Kiloparsec Scales
Authors:
Schlafly, E. F.; Peek, J. E. G.; Finkbeiner, D. P.; Green, G. M.
Publication:
eprint arXiv:1612.02818
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Astrophysics - Astrophysics of Galaxies
Comment:
11 pages, 7 figures, comments welcome
Bibliographic Code:
2016arXiv161202818S

Abstract

Near-infrared spectroscopy from APOGEE and wide-field optical photometry from Pan-STARRS1 have recently made possible precise measurements of the shape of the extinction curve for tens of thousands of stars, parameterized by R(V). These measurements revealed structures in R(V) with large angular scales, which are challenging to explain in existing dust paradigms. In this work, we combine three-dimensional maps of dust column density with R(V) measurements to constrain the three-dimensional distribution of R(V) in the Milky Way. We find that variations in R(V) are correlated on kiloparsec scales. In particular, most of the dust within one kiloparsec in the outer Galaxy, including many local molecular clouds (Orion, Taurus, Perseus, California, Cepheus), has a significantly lower R(V) than more distant dust in the Milky Way. These results provide new input to models of dust evolution and processing, and complicate application of locally derived extinction curves to more distant regions of the Milky Way and to other galaxies.

 

Title:
Full counting statistics of time of flight images
Authors:
Lovas, Izabella; Dóra, Balázs; Demler, Eugene; Zaránd, Gergely
Publication:
eprint arXiv:1612.02837
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Quantum Gases
Comment:
12 pages, 7 figures (including appendix)
Bibliographic Code:
2016arXiv161202837L

Abstract

Inspired by recent advances in cold atomic systems and non-equilibrium physics, we introduce a novel characterization scheme, the time of flight full counting statistics. We benchmark this method on an interacting one dimensional Bose gas, and show that there the time of flight image displays several universal regimes. Finite momentum fluctuations are observed at larger distances, where a crossover from exponential to Gamma distribution occurs upon decreasing momentum resolution. Zero momentum particles, on the other hand, obey a Gumbel distribution, characterizing the quantum fluctuations of the former quasi-condensate. Time of flight full counting statistics is demonstrated to capture thermalization processes after a quantum quench, and can be useful for characterizing exotic quantum states such as many-body localized systems or models of holography.

 

Title:
Optical and microwave control of germanium-vacancy center spins in diamond
Authors:
Siyushev, Petr; Metsch, Mathias H.; Ijaz, Aroosa; Binder, Jan M.; Bhaskar, Mihir K.; Sukachev, Denis D.; Sipahigil, Alp; Evans, Ruffin E.; Nguyen, Christian T.; Lukin, Mikhail D.; Hemmer, Philip R.; Palyanov, Yuri N.; Kupriyanov, Igor N.; Borzdov, Yuri M.; Rogers, Lachlan J.; Jelezko, Fedor
Publication:
eprint arXiv:1612.02947
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Quantum Physics, Condensed Matter - Materials Science
Comment:
6 pages, 4 figures
Bibliographic Code:
2016arXiv161202947S

Abstract

A solid-state system combining a stable spin degree of freedom with an efficient optical interface is highly desirable as an element for integrated quantum optical and quantum information systems. We demonstrate a bright color center in diamond with excellent optical properties and controllable electronic spin states. Specifically, we carry out detailed optical spectroscopy of a Germanium Vacancy (GeV) color center demonstrating optical spectral stability. Using an external magnetic field to lift the electronic spin degeneracy, we explore the spin degree of freedom as a controllable qubit. Spin polarization is achieved using optical pumping, and a spin relaxation time in excess of 20 $\mu$s is demonstrated. Optically detected magnetic resonance (ODMR) is observed in the presence of a resonant microwave field. ODMR is used as a probe to measure the Autler-Townes effect in a microwave-optical double resonance experiment. Superposition spin states were prepared using coherent population trapping, and a pure dephasing time of about 19 ns was observed. Prospects for realizing coherent quantum registers based on optically controlled GeV centers are discussed.

 

Title:
Quantum Nonlinear Optics with a Germanium-Vacancy Color Center in a Nanoscale Diamond Waveguide
Authors:
Bhaskar, Mihir K.; Sukachev, Denis D.; Sipahigil, Alp; Evans, Ruffin E.; Burek, Michael J.; Nguyen, Christian T.; Rogers, Lachlan J.; Siyushev, Petr; Metsch, Mathias H.; Park, Hongkun; Jelezko, Fedor; Lončar, Marko; Lukin, Mikhail D.
Publication:
eprint arXiv:1612.03036
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Quantum Physics, Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Optics
Comment:
5 pages and 5 figures. Supplemental Material, 3 pages and 1 figure, available as an ancillary file
Bibliographic Code:
2016arXiv161203036B

Abstract

We demonstrate a quantum nanophotonics platform based on germanium-vacancy (GeV) color centers in fiber-coupled diamond nanophotonic waveguides. We show that GeV optical transitions have a high quantum efficiency and are nearly lifetime-broadened in such nanophotonic structures. These properties yield an efficient interface between waveguide photons and a single GeV without the use of a cavity or slow-light waveguide. As a result, a single GeV center reduces waveguide transmission by $18 \pm 1 \%$ on resonance in a single pass. We use a nanophotonic interferometer to perform homodyne detection of GeV resonance fluorescence. By probing the photon statistics of the output field, we demonstrate that the GeV-waveguide system is nonlinear at the single-photon level.

 

Title:
Collective induced superradiant lineshifts
Authors:
Putnam, Gray; Lin, Guin-Dar; Yelin, Susanne
Publication:
eprint arXiv:1612.04477
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Physics - Atomic Physics
Comment:
5 pages, 4 figures
Bibliographic Code:
2016arXiv161204477P

Abstract

Superradiant decay is accompanied by two kinds of collective lineshifts, an induced shift and the spontaneous "collective Lamb shift." Both form as sum of dipole-dipole interaction-induced level shifts between atoms in the system. We have developed a procedure to obtain numerical results on this model that self-consistently incorporates the shifts. The induced shift displays large non-zero values early in the system evolution. In addition, its effect on the superradiant system is studied: there is only a very small dephasing effect on the decay rate. While the induced shift is largely absent in not-too strongly driven systems, this parameter region might provide a good experimental regime for measuring the collective Lamb shift. These results can have important consequences for highly sensitive systems, such as quantum information science or atomic clocks.

 

Title:
Logarithmic corrections to black hole entropy from Kerr/CFT
Authors:
Pathak, Abhishek; Porfyriadis, Achilleas P.; Strominger, Andrew; Varela, Oscar
Publication:
eprint arXiv:1612.04833
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
High Energy Physics - Theory
Bibliographic Code:
2016arXiv161204833P

Abstract

It has been shown by A. Sen that logarithmic corrections to the black hole area-entropy law are entirely determined macroscopically from the massless particle spectrum. They therefore serve as powerful consistency checks on any proposed enumeration of quantum black hole microstates. Sen's results include a macroscopic computation of the logarithmic corrections for a five-dimensional near extremal Kerr-Newman black hole. Here we compute these corrections microscopically using a stringy embedding of the Kerr/CFT correspondence and find perfect agreement.

 

Title:
Pan-STARRS Photometric and Astrometric Calibration
Authors:
Magnier, Eugene. A.; Schlafly, Edward. F.; Finkbeiner, Douglas P.; Tonry, J. L.; Goldman, B.; Röser, S.; Schilbach, E.; Chambers, K. C.; Flewelling, H. A.; Huber, M. E.; Price, P. A.; Sweeney, W. E.; Waters, C. Z.; Denneau, L.; Draper, P.; Hodapp, K. W.; Jedicke, R.; Kudritzki, R.-P.; Metcalfe, N.; Stubbs, C. W.; Wainscoast, R. J.
Publication:
eprint arXiv:1612.05242
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Astrophysics - Instrumentation and Methods for Astrophysics
Comment:
Pan-STARRS Public Release : Paper V
Bibliographic Code:
2016arXiv161205242M

Abstract

The Pan-STARRS\,1 $3\pi$ survey has produced photometry and astrometry covering the \approx 30,000 square degrees $\delta > -30$\degrees. This article describes the photometric and astrometric calibration of this survey.

 

Title:
A fiber-coupled diamond quantum nanophotonic interface
Authors:
Burek, Michael J.; Meuwly, Charles; Evans, Ruffin E.; Bhaskar, Mihir K.; Sipahigil, Alp; Meesala, Srujan; Sukachev, Denis D.; Nguyen, Christian T.; Pacheco, Jose L.; Bielejec, Edward; Lukin, Mikhail D.; Lončar, Marko
Publication:
eprint arXiv:1612.05285
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Optics
Bibliographic Code:
2016arXiv161205285B

Abstract

Color centers in diamond provide a promising platform for quantum optics in the solid state, with coherent optical transitions and long-lived electron and nuclear spins. Building upon recent demonstrations of nanophotonic waveguides and optical cavities in single-crystal diamond, we now demonstrate on-chip diamond nanophotonics with a high efficiency fiber-optical interface, achieving > 90% power coupling at visible wavelengths. We use this approach to demonstrate a bright source of narrowband single photons, based on a silicon-vacancy color center embedded within a waveguide-coupled diamond photonic crystal cavity. Our fiber-coupled diamond quantum nanophotonic interface results in a high, nearly 0.45 MHz, flux of narrowband single photons into a single mode fiber, enabling new possibilities for realizing quantum networks that interface multiple emitters, both on-chip and separated by long distances.

 

Title:
The Pan-STARRS1 Surveys
Authors:
Chambers, K. C.; Magnier, E. A.; Metcalfe, N.;... Finkbeiner, D. P.;... Stubbs, C. W.;... ; and 98 coauthors
Publication:
eprint arXiv:1612.05560
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - Solar and Stellar Astrophysics
Comment:
34 pages, 24 figures
Bibliographic Code:
2016arXiv161205560C

Abstract

Pan-STARRS1 has carried out a set of distinct synoptic imaging sky surveys including the $3\pi$ Steradian Survey and the Medium Deep Survey in 5 bands (\grizy). The mean 5$\sigma$ point source limiting sensitivities in the stacked 3$\pi$ Steradian Survey in \grizy are (23.3, 23.2, 23.1, 22.3, 21.4) respectively. The upper bound on the systematic uncertainty in the photometric calibration across the sky is 7-12 millimag depending on the bandpass. The systematic uncertainty of the astrometric calibration using the Gaia frame comes from a comparison of the results with Gaia: the standard deviation of the mean and median residuals ($ \Delta ra, \Delta dec $ ) are (2.3, 1.7) milliarcsec, and (3.1, 4.8) milliarcsec respectively. The Pan-STARRS system and the design of the PS1 surveys is described and an overview of the resulting image and catalog data products and their basic characteristics are described together with a summary of important results. The images, reduced data products, and derived data products from the Pan-STARRS1 surveys are available to the community from the Mikulski Archive for Space Telescopes (MAST) at STScI.

 

Title:
Microscopy of the interacting Harper-Hofstadter model in the few-body limit
Authors:
Tai, M. Eric; Lukin, Alexander; Rispoli, Matthew; Schittko, Robert; Menke, Tim; Borgnia, Dan; Preiss, Philipp M.; Grusdt, Fabian; Kaufman, Adam M.; Greiner, Markus
Publication:
eprint arXiv:1612.05631
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Quantum Gases, Quantum Physics
Bibliographic Code:
2016arXiv161205631T

Abstract

The interplay of magnetic fields and interacting particles can lead to exotic phases of matter exhibiting topological order and high degrees of spatial entanglement. While these phases were discovered in a solid-state setting, recent techniques have enabled the realization of gauge fields in systems of ultracold neutral atoms, offering a new experimental paradigm for studying these novel states of matter. This complementary platform holds promise for exploring exotic physics in fractional quantum Hall systems due to the microscopic manipulation and precision possible in cold atom systems. However, these experiments thus far have mostly explored the regime of weak interactions. Here, we show how strong interactions can modify the propagation of particles in a $2\times N$, real-space ladder governed by the Harper-Hofstadter model. We observe inter-particle interactions affect the populating of chiral bands, giving rise to chiral dynamics whose multi-particle correlations indicate both bound and free-particle character. The novel form of interaction-induced chirality observed in these experiments demonstrates the essential ingredients for future investigations of highly entangled topological phases of many-body systems.

 

Title:
Polaron-induced phonon localization and stiffening in rutile TiO$_2$
Authors:
Kolesov, Grigory; Kolesov, Boris A.; Kaxiras, Efthimios
Publication:
eprint arXiv:1612.05679
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Materials Science
Bibliographic Code:
2016arXiv161205679K

Abstract

Small polaron formation in transition metal oxides, like the prototypical material rutile TiO$_2$, remains a puzzle and a challenge to simple theoretical treatment. In our combined experimental and theoretical study, we examine this problem using Raman spectroscopy of photo-excited samples and real-time time-dependent density functional theory (RT-TDDFT), which employs Ehrenfest dynamics to couple the electronic and ionic subsystems. We observe experimentally the unexpected stiffening of the $A_{1g}$ phonon mode under UV illumination and provide a theoretical explanation for this effect. Our analysis also reveals a possible reason for the observed anomalous temperature-dependence of the Hall mobility. Small polaron formation in rutile TiO$_2$ is a strongly non-adiabatic process and is adequately described by Ehrenfest dynamics at time scales of polaron formation.

 

Title:
Coulomb drag between carbon nanotube and graphene
Authors:
Pillet, Jean-Damien; Cheng, Austin; Taniguchi, Takashi; Watanabe, Kenji; Kim, Philip
Publication:
eprint arXiv:1612.05992
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Mesoscale and Nanoscale Physics
Comment:
includes supplementary information
Bibliographic Code:
2016arXiv161205992P

Abstract

When two electrically isolated conductors are brought close, a current in one conductor can generate friction and drag electrons in the other via Coulomb interaction, thereby causing a charge imbalance in the dragged layer. This is known as Coulomb drag and has been used to investigate strongly correlated nature of low dimensional conductors. Here, we report the observation of Coulomb drag between a two-dimensional electron gas in graphene and a one-dimensional wire composed of a carbon nanotube. We find that drag occurs when the bulk of graphene is conducting, but is strongly suppressed in the quantum Hall regime when magnetic field confines conducting electrons to the edges of graphene and far from the nanotube. Out-of-equilibrium measurements show that transitions between quantized charge states of the nanotube induce either strong suppression or enhancement of drag signal.

 

Title:
Efficient quantum computation in a network with probabilistic gates and logical encoding
Authors:
Borregaard, Johannes; Sørensen, Anders S.; Cirac, Ignacio; Lukin, Mikhail D.
Publication:
eprint arXiv:1612.06812
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Quantum Physics
Comment:
5 pages, 4 figures
Bibliographic Code:
2016arXiv161206812B

Abstract

A new approach to efficient quantum computation with probabilistic gates is proposed and analyzed in both a local and non-local setting. It combines heralded gates previously studied for atom or atom-like qubits with logical encoding from linear optical quantum computation in order to perform high fidelity quantum gates across a quantum network. The error-detecting properties of the heralded operations ensure high fidelity while the encoding makes it possible to correct for failed attempts such that deterministic and high-quality gates can be achieved. Importantly, this is robust to photon loss, which is typically the main obstacle to photonic based quantum information processing. Overall this approach opens a novel path towards quantum networks with atomic nodes and photonic links.

 

Title:
Quadrality for Supersymmetric Matrix Models
Authors:
Franco, Sebastian; Lee, Sangmin; Seong, Rak-Kyeong; Vafa, Cumrun
Publication:
eprint arXiv:1612.06859
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
High Energy Physics - Theory, Mathematical Physics
Comment:
46 pages, 18 figures
Bibliographic Code:
2016arXiv161206859F

Abstract

We introduce a new duality for $\mathcal{N}=1$ supersymmetric gauged matrix models. This $0d$ duality is an order 4 symmetry, namely an equivalence between four different theories, hence we call it Quadrality. Our proposal is motivated by mirror symmetry, but is not restricted to theories with a D-brane realization and holds for general $\mathcal{N}=1$ matrix models. We present various checks of the proposal, including the matching of: global symmetries, anomalies, deformations and the chiral ring. We also consider quivers and the corresponding quadrality networks. Finally, we initiate the study of matrix models that arise on the worldvolume of D(-1)-branes probing toric Calabi-Yau 5-folds.

 

Title:
Holographic quantum matter
Authors:
Hartnoll, Sean A.; Lucas, Andrew; Sachdev, Subir
Publication:
eprint arXiv:1612.07324
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
High Energy Physics - Theory, Condensed Matter - Strongly Correlated Electrons
Comment:
6+347 pages, 43 figures; Draft of a review article for hep-th and cond-mat readers, comments welcome
Bibliographic Code:
2016arXiv161207324H

Abstract

We present a review of theories of states of quantum matter without quasiparticle excitations. Solvable examples of such states are provided through a holographic duality with gravitational theories in an emergent spatial dimension. We review the duality between gravitational backgrounds and the various states of quantum matter which live on the boundary. We then describe quantum matter at a fixed commensurate density (often described by conformal field theories), and also compressible quantum matter with variable density, providing an extensive discussion of transport in both cases. We present a unified discussion of the holographic theory of transport with memory matrix and hydrodynamic methods, allowing a direct connection to experimentally realized quantum matter. We also explore other important challenges in non-quasiparticle physics, including symmetry broken phases such as superconductors and non-equilibrium dynamics.

 

Title:
Electric Dipole Moments in Natural Supersymmetry
Authors:
Nakai, Yuichiro; Reece, Matthew
Publication:
eprint arXiv:1612.08090
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
High Energy Physics - Phenomenology
Comment:
37 pages plus appendices, 16 figures
Bibliographic Code:
2016arXiv161208090N

Abstract

We discuss electric dipole moments (EDMs) in the framework of CP-violating natural supersymmetry (SUSY). Recent experimental results have significantly tightened constraints on the EDMs of electrons and of mercury, and substantial further progress is expected in the near future. We assess how these results constrain the parameter space of natural SUSY. In addition to our discussion of SUSY, we provide a set of general formulas for two-loop fermion EDMs, which can be applied to a wide range of models of new physics. In the SUSY context, the two-loop effects of stops and charginos respectively constrain the phases of $A_t \mu$ and $M_2 \mu$ to be small in the natural part of parameter space. If the Higgs mass is lifted to 125 GeV by a new tree-level superpotential interaction and soft term with CP-violating phases, significant EDMs can arise from the two-loop effects of $W$ bosons and tops. We compare the bounds arising from EDMs to those from other probes of new physics including colliders, $b \to s \gamma$, and dark matter searches. Importantly, improvements in reach not only constrain higher masses, but require the phases to be significantly smaller in the natural parameter space at low mass. The required smallness of phases sharpens the CP problem of natural SUSY model building.

 

Title:
Frictional magneto-Coulomb drag in graphene double-layer heterostructure
Authors:
Liu, Xiaomeng; Wang, Lei; Chung Fong, Kin; Gao, Yuanda; Maher, Patrick; Watanabe, Kenji; Taniguchi, Takashi; Hone, James; Dean, Cory; Kim, Philip
Publication:
eprint arXiv:1612.08308
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Mesoscale and Nanoscale Physics
Comment:
5 pages, 3 figures
Bibliographic Code:
2016arXiv161208308L

Abstract

Coulomb interaction between two closely spaced parallel layers of electron system can generate the frictional drag effect by interlayer Coulomb scattering. Employing graphene double layers separated by few layer hexagonal boron nitride (hBN), we investigate density tunable magneto- and Hall-drag under strong magnetic fields. The observed large magneto-drag and Hall-drag signals can be related with Laudau level (LL) filling status of the drive and drag layers. We find that the sign and magnitude of the magneto- and Hall-drag resistivity tensor can be quantitatively correlated to the variation of magneto-resistivity tensors in the drive and drag layers, confirming a theoretical formula for magneto-drag in the quantum Hall regime. The observed weak temperature dependence and $\sim B^2$ dependence of the magneto-drag are qualitatively explained by Coulomb scattering phase-space argument.

 

Title:
Experimental realization of a long-range antiferromagnet in the Hubbard model with ultracold atoms
Authors:
Mazurenko, Anton; Chiu, Christie S.; Ji, Geoffrey; Parsons, Maxwell F.; Kanász-Nagy, Márton; Schmidt, Richard; Grusdt, Fabian; Demler, Eugene; Greif, Daniel; Greiner, Markus
Publication:
eprint arXiv:1612.08436
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Quantum Gases
Comment:
15 pages, 9 figures
Bibliographic Code:
2016arXiv161208436M

Abstract

Many exotic phenomena in strongly correlated electron systems emerge from the interplay between spin and motional degrees of freedom. For example, doping an antiferromagnet gives rise to interesting phases including pseudogap states and high-temperature superconductors. A promising route towards achieving a complete understanding of these materials begins with analytic and computational analysis of simplified models. Quantum simulation has recently emerged as a complementary approach towards understanding these models. Ultracold fermions in optical lattices offer the potential to answer open questions on the low-temperature regime of the doped Hubbard model, which is thought to capture essential aspects of the cuprate superconductor phase diagram but is numerically intractable in that parameter regime. A new perspective is afforded by quantum gas microscopy of fermions, which allows readout of magnetic correlations at the site-resolved level. Here we report the realization of an antiferromagnet in a repulsively interacting Fermi gas on a 2D square lattice of approximately 80 sites. Using site-resolved imaging, we detect (finite-size) antiferromagnetic long-range order (LRO) through the development of a peak in the spin structure factor and the divergence of the correlation length that reaches the size of the system. At our lowest temperature of T/t = 0.25(2) we find strong order across the entire sample. Our experimental platform enables doping away from half filling, where pseudogap states and stripe ordering are expected, but theoretical methods become numerically intractable. In this regime we find that the antiferromagnetic LRO persists to hole dopings of about 15%, providing a guideline for computational methods. Our results demonstrate that quantum gas microscopy of ultracold fermions in optical lattices can now address open questions on the low-temperature Hubbard model.

 

Title:
Braiding Statistics and Link Invariants of Bosonic/Fermionic Topological Quantum Matter in 2+1 and 3+1 dimensions
Authors:
Putrov, Pavel; Wang, Juven; Yau, Shing-Tung
Publication:
eprint arXiv:1612.09298
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons
Comment:
36 pages, 8 figures, 3 tables. On 2+1D and 3+1D TQFTs / spin TQFTs
Bibliographic Code:
2016arXiv161209298P

Abstract

Topological Quantum Field Theories (TQFTs) pertinent to some emergent low energy phenomena of condensed matter lattice models in 2+1 and 3+1 dimensions are explored. Many of our field theories are highly-interacting without the free quadratic analogs. Some of our bosonic TQFTs can be regarded as the continuous field theory formulation of Dijkgraaf-Witten twisted discrete gauge theories. Other bosonic TQFTs beyond the Dijkgraaf-Witten description and all fermionic TQFTs (namely, the spin TQFTs) are either higher-form gauge theories where particles must have strings attached, or fermionic discrete gauge theories obtained by gauging the fermionic Symmetry-Protected Topological states (SPTs). We analytically calculate both the Abelian and non-Abelian braiding statistics data of anyonic particle and string excitations in these theories, where the statistics data can one-to-one characterize the underlying topological orders of TQFTs. In other words, we calculate path integral expectation values of links formed by line and surface operators in these TQFTs. The acquired link invariants include not only the familiar Aharonov-Bohm linking number, but also Milnor triple linking number in 2+1 dimensions, triple and quadruple linking numbers of surfaces, and intersection number of surfaces in 3+1 dimensions. We also construct new spin TQFTs for which the corresponding knot/link invariants are Arf(-Brown-Kervaire), Sato-Levine and others. We propose a new relation between the fermionic SPT partition function and the Rokhlin invariant. We use these invariants and other physical observables, including ground state degeneracy, modular $\mathcal{S}^{xy}$ and $\mathcal{T}^{xy}$ matrices, and the partition function on $\mathbb{RP}^3$ manifold, to identify all $\mathbb{Z}_8$ classes of gauged $\mathbb{Z_2}^f\times\mathbb{Z}$ fermionic SPTs with continous spin-TQFTs.

 

Title:
Methods, Analysis, and the Treatment of Systematic Errors for the Electron Electric Dipole Moment Search in Thorium Monoxide
Authors:
ACME Collaboration; Baron, Jacob; Campbell, Wes C.; DeMille, David; Doyle, John M.; Gabrielse, Gerald; Gurevich, Yulia V.; Hess, Paul W.; Hutzler, Nicholas R.; Kirilov, Emil; Kozyryev, Ivan; O'Leary, Brendon R.; Panda, Cristian D.; Parsons, Maxwell F.; Spaun, Benjamin; Vutha, Amar C.; West, Adam D.; West, Elizabeth P.
Publication:
eprint arXiv:1612.09318
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Physics - Atomic Physics, High Energy Physics - Phenomenology
Comment:
81 pages, 37 figures, submitted to NJP
Bibliographic Code:
2016arXiv161209318A

Abstract

We recently set a new limit on the electric dipole moment of the electron (eEDM) (J. Baron et al., ACME collaboration, Science 343 (2014), 269-272), which represented an order-of-magnitude improvement on the previous limit and placed more stringent constraints on many CP-violating extensions to the Standard Model. In this paper we discuss the measurement in detail. The experimental method and associated apparatus are described, together with the techniques used to isolate the eEDM signal. In particular, we detail the way experimental switches were used to suppress effects that can mimic the signal of interest. The methods used to search for systematic errors, and models explaining observed systematic errors, are also described. We briefly discuss possible improvements to the experiment.

 

Title:
Quasinormal ringing on the brane
Authors:
Chung, Hyeyoun; Randall, Lisa; Rodriguez, Maria J.; Varela, Oscar
Publication:
Classical and Quantum Gravity, Volume 33, Issue 24, article id. 245013 (2016). (CQGra Homepage)
Publication Date:
12/2016
Origin:
IOP
DOI:
10.1088/0264-9381/33/24/245013
Bibliographic Code:
2016CQGra..33x5013C

Abstract

While the linear behavior of gravity in braneworld models is well understood, much less is known about full nonlinear gravitational effects. Even when they agree at the linear level, these could be expected to distinguish braneworlds from a lower-dimensional theory with no brane. Black holes are a good testing ground for such studies, as they are nonlinear solutions that would be expected to reflect the background geometry. In particular, we assess the role of black hole quasinormal modes (QNMs) in gravitational experiments devised to be sensitive to the existence of the brane, in a lower-dimensional setting where we have analytical control. We compute QNMs of brane-localized black holes and find that they follow the entropy of the corresponding black hole. This observation allows us to conclude that, surprisingly, the scattering problem we consider, at least in some regimes, does not distinguish between nonlinear gravitational effects of black holes in AdS space with a brane and black holes in a spacetime of one lower dimension.

 

Title:
Luminosity determination in pp collisions at √{s} = 8 TeV using the ATLAS detector at the LHC
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2848 coauthors
Publication:
The European Physical Journal C, Volume 76, Issue 12, article id.653, 45 pp. (EPJC Homepage)
Publication Date:
12/2016
Origin:
SPRINGER
Abstract Copyright:
(c) 2016: CERN for the benefit of the
DOI:
10.1140/epjc/s10052-016-4466-1
Bibliographic Code:
2016EPJC...76..653A

Abstract

The luminosity determination for the ATLAS detector at the LHC during pp collisions at √{s} = 8 TeV in 2012 is presented. The evaluation of the luminosity scale is performed using several luminometers, and comparisons between these luminosity detectors are made to assess the accuracy, consistency and long-term stability of the results. A luminosity uncertainty of δ L/L = ± 1.9% is obtained for the 22.7 fb^{-1} of pp collision data delivered to ATLAS at √{s} = 8 TeV in 2012.

 

Title:
Test of CP invariance in vector-boson fusion production of the Higgs boson using the Optimal Observable method in the ditau decay channel with the ATLAS detector
Authors:
Aad, G.; Abbott, B.; Abdinov, O.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2863 coauthors
Publication:
The European Physical Journal C, Volume 76, Issue 12, article id.658, 25 pp. (EPJC Homepage)
Publication Date:
12/2016
Origin:
SPRINGER
Abstract Copyright:
(c) 2016: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-016-4499-5
Bibliographic Code:
2016EPJC...76..658A

Abstract

A test of CP invariance in Higgs boson production via vector-boson fusion using the method of the Optimal Observable is presented. The analysis exploits the decay mode of the Higgs boson into a pair of τ leptons and is based on 20.3 fb^{-1} of proton-proton collision data at √{s} = 8 TeV collected by the ATLAS experiment at the LHC. Contributions from CP-violating interactions between the Higgs boson and electroweak gauge bosons are described in an effective field theory framework, in which the strength of CP violation is governed by a single parameter tilde{d}. The mean values and distributions of CP-odd observables agree with the expectation in the Standard Model and show no sign of CP violation. The CP-mixing parameter tilde{d} is constrained to the interval (-0.11,0.05) at 68% confidence level, consistent with the Standard Model expectation of tilde{d}=0.

 

Title:
Measurement of the photon identification efficiencies with the ATLAS detector using LHC Run-1 data
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2849 coauthors
Publication:
The European Physical Journal C, Volume 76, Issue 12, article id.666, 42 pp. (EPJC Homepage)
Publication Date:
12/2016
Origin:
SPRINGER
Abstract Copyright:
(c) 2016: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-016-4507-9
Bibliographic Code:
2016EPJC...76..666A

Abstract

The algorithms used by the ATLAS Collaboration to reconstruct and identify prompt photons are described. Measurements of the photon identification efficiencies are reported, using 4.9 fb^{-1} of pp collision data collected at the LHC at √{s} = 7 {TeV} and 20.3 fb^{-1} at √{s} = 8 {TeV}. The efficiencies are measured separately for converted and unconverted photons, in four different pseudorapidity regions, for transverse momenta between 10 {GeV} and 1.5 {TeV}. The results from the combination of three data-driven techniques are compared to the predictions from a simulation of the detector response, after correcting the electromagnetic shower momenta in the simulation for the average differences observed with respect to data. Data-to-simulation efficiency ratios used as correction factors in physics measurements are determined to account for the small residual efficiency differences. These factors are measured with uncertainties between 0.5% and 10% in 7 {TeV} data and between 0.5% and 5.6% in 8 {TeV} data, depending on the photon transverse momentum and pseudorapidity.

 

Title:
Measurement of the boverline{b} dijet cross section in pp collisions at √{s} = 7 TeV with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2849 coauthors
Publication:
The European Physical Journal C, Volume 76, Issue 12, article id.670, 24 pp. (EPJC Homepage)
Publication Date:
12/2016
Origin:
SPRINGER
Abstract Copyright:
(c) 2016: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-016-4521-y
Bibliographic Code:
2016EPJC...76..670A

Abstract

The dijet production cross section for jets containing a b-hadron ( b-jets) has been measured in proton-proton collisions with a centre-of-mass energy of √{s} = 7 TeV, using the ATLAS detector at the LHC. The data used correspond to an integrated luminosity of 4.2 {fb}^{-1}. The cross section is measured for events with two identified b-jets with a transverse momentum p_{ {T}} > 20 GeV and a minimum separation in the η -φ plane of Δ R = 0.4. At least one of the jets in the event is required to have p_{ {T}} > 270 GeV. The cross section is measured differentially as a function of dijet invariant mass, dijet transverse momentum, boost of the dijet system, and the rapidity difference, azimuthal angle and angular distance between the b-jets. The results are compared to different predictions of leading order and next-to-leading order perturbative quantum chromodynamics matrix elements supplemented with models for parton-showers and hadronization.

 

Title:
Search for squarks and gluinos in events with hadronically decaying tau leptons, jets and missing transverse momentum in proton-proton collisions at √{s}=13 TeV recorded with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2852 coauthors
Publication:
The European Physical Journal C, Volume 76, Issue 12, article id. #683, 33 pp. (EPJC Homepage)
Publication Date:
12/2016
Origin:
SPRINGER
Abstract Copyright:
(c) 2016: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-016-4481-2
Bibliographic Code:
2016EPJC...76..683A

Abstract

A search for supersymmetry in events with large missing transverse momentum, jets, and at least one hadronically decaying tau lepton has been performed using 3.2 fb^{-1} of proton-proton collision data at √{s}=13{ TeV} recorded by the ATLAS detector at the Large Hadron Collider in 2015. Two exclusive final states are considered, with either exactly one or at least two tau leptons. No excess over the Standard Model prediction is observed in the data. Results are interpreted in the context of gauge-mediated supersymmetry breaking and a simplified model of gluino pair production with tau-rich cascade decays, substantially improving on previous limits. In the GMSB model considered, supersymmetry-breaking scale (Λ ) values below 92 { TeV} are excluded at the 95% confidence level, corresponding to gluino masses below 2000 { GeV}. For large values of tan β , values of Λ up to 107 { TeV} and gluino masses up to 2300 { GeV} are excluded. In the simplified model, gluino masses are excluded up to 1570 { GeV} for neutralino masses around 100 { GeV}. Neutralino masses below 700 { GeV} are excluded for all gluino masses between 800 and 1500 { GeV}, while the strongest exclusion of 750 { GeV} is achieved for gluino masses around 1450 { GeV}.

 

Title:
Ambipolar transport and magneto-resistance crossover in a Mott insulator, Sr2IrO4
Authors:
Ravichandran, J.; Serrao, C. R.; Efetov, D. K.; Yi, D.; Oh, Y. S.; Cheong, S.-W.; Ramesh, R.; Kim, P.
Publication:
Journal of Physics: Condensed Matter, Volume 28, Issue 50, article id. 505304 (2016).
Publication Date:
12/2016
Origin:
IOP
DOI:
10.1088/0953-8984/28/50/505304
Bibliographic Code:
2016JPCM...28X5304R

Abstract

Electric field effect (EFE) controlled magnetoelectric transport in thin films of undoped and La-doped Sr2IrO4 (SIO) is investigated using ionic liquid gating. The temperature dependent resistance measurements exhibit insulating behavior in chemically and EFE doped samples with the band filling up to 10%. The ambipolar transport across the Mott gap is demonstrated by EFE tuning of the channel resistance and chemical doping. We observe a crossover from high temperature negative to low temperature positive magnetoresistance around  ˜80-90 K, irrespective of the filling. This temperature and magnetic field dependent crossover is discussed in the light of conduction mechanisms of SIO, especially variable range hopping (VRH), and its relevance to the insulating ground state of SIO.

 

Title:
A Synoptic Map of Halo Substructures from the Pan-STARRS1 3π Survey
Authors:
Bernard, Edouard J.; Ferguson, Annette M. N.; Schlafly, Edward F.; Martin, Nicolas F.; Rix, Hans-Walter; Bell, Eric F.; Finkbeiner, Douglas P.; Goldman, Bertrand; Martínez-Delgado, David; Sesar, Branimir; Wyse, Rosemary F. G.; Burgett, William S.; Chambers, Kenneth C.; Draper, Peter W.; Hodapp, Klaus W.; Kaiser, Nicholas; Kudritzki, Rolf-Peter; Magnier, Eugene A.; Metcalfe, Nigel; Wainscoat, Richard J.; Waters, Christopher
Publication:
Monthly Notices of the Royal Astronomical Society, Volume 463, Issue 2, p.1759-1768 (MNRAS Homepage)
Publication Date:
12/2016
Origin:
OUP
Astronomy Keywords:
Hertzsprung-Russell and colour-magnitude diagrams, surveys, Galaxy: halo, Galaxy: structure
Abstract Copyright:
2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society
DOI:
10.1093/mnras/stw2134
Bibliographic Code:
2016MNRAS.463.1759B

Abstract

We present a panoramic map of the entire Milky Way halo north of δ ˜ -30° (˜30 000 deg2), constructed by applying the matched-filter technique to the Pan-STARRS1 3π Survey data set. Using single-epoch photometry reaching to g ˜22, we are sensitive to stellar substructures with heliocentric distances between 3.5 and ˜35 kpc. We recover almost all previously reported streams in this volume and demonstrate that several of these are significantly more extended than earlier data sets have indicated. In addition, we also report five new candidate stellar streams. One of these features appears significantly broader and more luminous than the others and is likely the remnant of a dwarf galaxy. The other four streams are consistent with a globular cluster origin, and three of these are rather short in projection (≲ 10°), suggesting that streams like Ophiuchus may not be that rare. Finally, a significant number of more marginal substructures are also revealed by our analysis; many of these features can also be discerned in matched-filter maps produced by other authors from SDSS data, and hence they are very likely to be genuine. However, the extant 3π data is currently too shallow to determine their properties or produce convincing colour-magnitude diagrams. The global view of the Milky Way provided by Pan-STARRS1 provides further evidence for the important role of both globular cluster disruption and dwarf galaxy accretion in building the Milky Way's stellar halo.

 

Title:
ATLAS Collaboration
Authors:
Aad, G.; Abbott, B.; Abdallah, J.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2805 coauthors
Publication:
Nuclear Physics, Section A, Volume 956, p. 922-944.
Publication Date:
12/2016
Origin:
ELSEVIER
Abstract Copyright:
(c) 2016 Elsevier Science B.V. All rights reserved.
DOI:
10.1016/S0375-9474(16)30232-9
Bibliographic Code:
2016NuPhA.956..922A

Abstract

Not Available

 

Title:
Measurement of W+W- production in association with one jet in proton-proton collisions at √{ s} = 8TeV with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2848 coauthors
Publication:
Physics Letters B, Volume 763, p. 114-133.
Publication Date:
12/2016
Origin:
ELSEVIER
Abstract Copyright:
(c) 2016 Elsevier Science B.V. All rights reserved.
DOI:
10.1016/j.physletb.2016.10.014
Bibliographic Code:
2016PhLB..763..114A

Abstract

The production of W boson pairs in association with one jet in pp collisions at √{ s} = 8 TeV is studied using data corresponding to an integrated luminosity of 20.3 fb-1 collected by the ATLAS detector during 2012 at the CERN Large Hadron Collider. The cross section is measured in a fiducial phase-space region defined by the presence of exactly one electron and one muon, missing transverse momentum and exactly one jet with a transverse momentum above 25 GeV and a pseudorapidity of | η | < 4.5. The leptons are required to have opposite electric charge and to pass transverse momentum and pseudorapidity requirements. The fiducial cross section is found to be σWWfid,1-jet = 136 ± 6 (stat) ± 14 (syst) ± 3 (lumi) fb. In combination with a previous measurement restricted to leptonic final states with no associated jets, the fiducial cross section of WW production with zero or one jet is measured to be σWWfid, ≤ 1-jet = 511 ± 9 (stat) ± 26 (syst) ± 10 (lumi) fb. The ratio of fiducial cross sections in final states with one and zero jets is determined to be 0.36 ± 0.05. Finally, a total cross section extrapolated from the fiducial measurement of WW production with zero or one associated jet is reported. The measurements are compared to theoretical predictions and found in good agreement.

 

Title:
Search for dark matter produced in association with a hadronically decaying vector boson in pp collisions at √{ s} = 13 TeV with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2851 coauthors
Publication:
Physics Letters B, Volume 763, p. 251-268.
Publication Date:
12/2016
Origin:
ELSEVIER
Abstract Copyright:
(c) 2016 Elsevier Science B.V. All rights reserved.
DOI:
10.1016/j.physletb.2016.10.042
Bibliographic Code:
2016PhLB..763..251A

Abstract

A search is presented for dark matter produced in association with a hadronically decaying W or Z boson using 3.2 fb-1 of pp collisions at √{ s} = 13 TeV recorded by the ATLAS detector at the Large Hadron Collider. Events with a hadronic jet compatible with a W or Z boson and with large missing transverse momentum are analysed. The data are consistent with the Standard Model predictions and are interpreted in terms of both an effective field theory and a simplified model containing dark matter.

 

Title:
Transverse momentum, rapidity, and centrality dependence of inclusive charged-particle production in √{sNN} = 5.02 TeVp + Pb collisions measured by the ATLAS experiment
Authors:
Aad, G.; Abbott, B.; Abdallah, J.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2842 coauthors
Publication:
Physics Letters B, Volume 763, p. 313-336.
Publication Date:
12/2016
Origin:
ELSEVIER
Abstract Copyright:
(c) 2016 Elsevier Science B.V. All rights reserved.
DOI:
10.1016/j.physletb.2016.10.053
Bibliographic Code:
2016PhLB..763..313A

Abstract

Measurements of the per-event charged-particle yield as a function of the charged-particle transverse momentum and rapidity are performed using p + Pb collision data collected by the ATLAS experiment at the LHC at a centre-of-mass energy of √{sNN} = 5.02TeV. Charged particles are reconstructed over pseudorapidity | η | < 2.3 and transverse momentum between 0.1 GeV and 22 GeV in a dataset corresponding to an integrated luminosity of 1 μb-1. The results are presented in the form of charged-particle nuclear modification factors, where the p + Pb charged-particle multiplicities are compared between central and peripheral p + Pb collisions as well as to charged-particle cross sections measured in pp collisions. The p + Pb collision centrality is characterized by the total transverse energy measured in - 4.9 < η < - 3.1, which is in the direction of the outgoing lead beam. Three different estimations of the number of nucleons participating in the p + Pb collision are carried out using the Glauber model and two Glauber-Gribov colour-fluctuation extensions to the Glauber model. The values of the nuclear modification factors are found to vary significantly as a function of rapidity and transverse momentum. A broad peak is observed for all centralities and rapidities in the nuclear modification factors for charged-particle transverse momentum values around 3 GeV. The magnitude of the peak increases for more central collisions as well as rapidity ranges closer to the direction of the outgoing lead nucleus.

 

Title:
Dynamical Cooper pairing in nonequilibrium electron-phonon systems
Authors:
Knap, Michael; Babadi, Mehrtash; Refael, Gil; Martin, Ivar; Demler, Eugene
Publication:
Physical Review B, Volume 94, Issue 21, id.214504 (PhRvB Homepage)
Publication Date:
12/2016
Origin:
APS
Abstract Copyright:
2016: American Physical Society
DOI:
10.1103/PhysRevB.94.214504
Bibliographic Code:
2016PhRvB..94u4504K

Abstract

We analyze Cooper pairing instabilities in strongly driven electron-phonon systems. The light-induced nonequilibrium state of phonons results in a simultaneous increase of the superconducting coupling constant and the electron scattering. We demonstrate that the competition between these effects leads to an enhanced superconducting transition temperature in a broad range of parameters. Our results may explain the observed transient enhancement of superconductivity in several classes of materials upon irradiation with high intensity pulses of terahertz light, and may pave new ways for engineering high-temperature light-induced superconducting states.

 

Title:
Electric field tuning of band offsets in transition metal dichalcogenides
Authors:
Huang, Dennis; Kaxiras, Efthimios
Publication:
Physical Review B, Volume 94, Issue 24, id.241303 (PhRvB Homepage)
Publication Date:
12/2016
Origin:
APS
Abstract Copyright:
2016: American Physical Society
DOI:
10.1103/PhysRevB.94.241303
Bibliographic Code:
2016PhRvB..94x1303H

Abstract

We use first-principles calculations to investigate the band structure evolution of W X2 /Mo X2 (X = S, Se) heterobilayers under a perpendicular electric field. We characterize the extent to which the type II band alignment in these compounds can be tuned or inverted electrostatically. Our results demonstrate two effects of the stacking configuration. First, different stackings produce different net dipole moments, resulting in band offset variations that are larger than 0.1 eV. Second, based on symmetry constraints that depend on stacking, a perpendicular electric field may hybridize W X2 and Mo X2 bands that cross at the Brillouin zone corner K . Our results suggest that external electric fields can be used to tune the physics of intralayer and interlayer excitons in heterobilayers of transition metal dichalcogenides.

 

Title:
Constraints on large extra dimensions from the MINOS experiment
Authors:
Adamson, P.; Anghel, I.; Aurisano, A.;... Feldman, G. J.;... and 117 coauthors; Minos Collaboration
Publication:
Physical Review D, Volume 94, Issue 11, id.111101 (PhRvD Homepage)
Publication Date:
12/2016
Origin:
APS
Abstract Copyright:
2016: American Physical Society
DOI:
10.1103/PhysRevD.94.111101
Bibliographic Code:
2016PhRvD..94k1101A

Abstract

We report new constraints on the size of large extra dimensions from data collected by the MINOS experiment between 2005 and 2012. Our analysis employs a model in which sterile neutrinos arise as Kaluza-Klein states in large extra dimensions and thus modify the neutrino oscillation probabilities due to mixing between active and sterile neutrino states. Using Fermilab's Neutrinos at the Main Injector beam exposure of 10.56 ×1 020 protons on target, we combine muon neutrino charged current and neutral current data sets from the Near and Far Detectors and observe no evidence for deviations from standard three-flavor neutrino oscillations. The ratios of reconstructed energy spectra in the two detectors constrain the size of large extra dimensions to be smaller than 0.45 μ m at 90% C.L. in the limit of a vanishing lightest active neutrino mass. Stronger limits are obtained for nonvanishing masses.

 

Title:
Multitracing anisotropic non-Gaussianity with galaxy shapes
Authors:
Chisari, Nora Elisa; Dvorkin, Cora; Schmidt, Fabian; Spergel, David N.
Publication:
Physical Review D, Volume 94, Issue 12, id.123507 (PhRvD Homepage)
Publication Date:
12/2016
Origin:
APS
Abstract Copyright:
2016: American Physical Society
DOI:
10.1103/PhysRevD.94.123507
Bibliographic Code:
2016PhRvD..94l3507C

Abstract

Correlations between intrinsic galaxy shapes on large scales arise due to the effect of the tidal field of the large-scale structure. Anisotropic primordial non-Gaussianity induces a distinct scale-dependent imprint in these tidal alignments on large scales. Motivated by the observational finding that the alignment strength of luminous red galaxies depends on how galaxy shapes are measured, we study the use of two different shape estimators as a multitracer probe of intrinsic alignments. We show, by means of a Fisher analysis, that this technique promises a significant improvement on anisotropic non-Gaussianity constraints over a single-tracer method. For future weak lensing surveys, the uncertainty in the anisotropic non-Gaussianity parameter, A2, is forecast to be σ (A2)≈50 , ˜40 % smaller than currently available constraints from the bispectrum of the cosmic microwave background. This corresponds to an improvement of a factor of 4-5 over the uncertainty from a single-tracer analysis.

 

Title:
Direct Approach to Quantum Tunneling
Authors:
Andreassen, Anders; Farhi, David; Frost, William; Schwartz, Matthew D.
Publication:
Physical Review Letters, Volume 117, Issue 23, id.231601 (PhRvL Homepage)
Publication Date:
12/2016
Origin:
APS
Abstract Copyright:
2016: American Physical Society
DOI:
10.1103/PhysRevLett.117.231601
Bibliographic Code:
2016PhRvL.117w1601A

Abstract

The decay rates of quasistable states in quantum field theories are usually calculated using instanton methods. Standard derivations of these methods rely in a crucial way upon deformations and analytic continuations of the physical potential and on the saddle-point approximation. While the resulting procedure can be checked against other semiclassical approaches in some one-dimensional cases, it is challenging to trace the role of the relevant physical scales, and any intuitive handle on the precision of the approximations involved is at best obscure. In this Letter, we use a physical definition of the tunneling probability to derive a formula for the decay rate in both quantum mechanics and quantum field theory directly from the Minkowski path integral, without reference to unphysical deformations of the potential. There are numerous benefits to this approach, from nonperturbative applications to precision calculations and aesthetic simplicity.

 

Title:
Mutation at Expanding Front of Self-Replicating Colloidal Clusters
Authors:
Tanaka, Hidenori; Zeravcic, Zorana; Brenner, Michael P.
Publication:
Physical Review Letters, Volume 117, Issue 23, id.238004 (PhRvL Homepage)
Publication Date:
12/2016
Origin:
APS
Abstract Copyright:
2016: American Physical Society
DOI:
10.1103/PhysRevLett.117.238004
Bibliographic Code:
2016PhRvL.117w8004T

Abstract

We construct a scheme for self-replicating square clusters of particles in two spatial dimensions, and validate it with computer simulations in a finite-temperature heat bath. We find that the self-replication reactions propagate through the bath in the form of Fisher waves. Our model reflects existing colloidal systems, but is simple enough to allow simulation of many generations and thereby the first study of evolutionary dynamics in an artificial system. By introducing spatially localized mutations in the replication rules, we show that the mutated cluster population can survive and spread with the expanding front in circular sectors of the colony.

 

Title:
Quasi-Many-Body Localization in Translation-Invariant Systems
Authors:
Yao, N. Y.; Laumann, C. R.; Cirac, J. I.; Lukin, M. D.; Moore, J. E.
Publication:
Physical Review Letters, Volume 117, Issue 24, id.240601 (PhRvL Homepage)
Publication Date:
12/2016
Origin:
APS
Abstract Copyright:
2016: American Physical Society
DOI:
10.1103/PhysRevLett.117.240601
Bibliographic Code:
2016PhRvL.117x0601Y

Abstract

We examine localization phenomena associated with generic, high entropy, states of a translation-invariant, one-dimensional spin ladder. At early times, we find slow growth of entanglement entropy consistent with the known phenomenology of many-body localization in disordered, interacting systems. At intermediate times, however, anomalous diffusion sets in, leading to full spin polarization decay on an exponentially activated time scale. We identify a single length scale which parametrically controls both the spin transport times and the apparent divergence of the susceptibility to spin glass ordering. Ultimately, at the latest times, the exponentially slow anomalous diffusion gives way to diffusive thermal behavior. We dub the intermediate dynamical behavior, which persists over many orders of magnitude in time, quasi-many-body localization.

 

Title:
Anomalous Conductances in an Ultracold Quantum Wire
Authors:
Kanász-Nagy, M.; Glazman, L.; Esslinger, T.; Demler, E. A.
Publication:
Physical Review Letters, Volume 117, Issue 25, id.255302 (PhRvL Homepage)
Publication Date:
12/2016
Origin:
APS
Abstract Copyright:
2016: American Physical Society
DOI:
10.1103/PhysRevLett.117.255302
Bibliographic Code:
2016PhRvL.117y5302K

Abstract

We analyze the recently measured anomalous transport properties of an ultracold gas through a ballistic constriction [S. Krinner et al., Proc. Natl. Acad. Sci. U.S.A. 113, 8144 (2016)]. The quantized conductance observed at weak interactions increases severalfold as the gas is made strongly interacting, which cannot be explained by the Landauer theory of single-channel transport. We show that this phenomenon is due to the multichannel Andreev reflections at the edges of the constriction, where the interaction and confinement result in a superconducting state. Andreev processes convert atoms of otherwise reflecting channels into the condensate propagating through the constriction, leading to a significant excess conductance. Furthermore, we find the spin conductance being suppressed by superconductivity; the agreement with experiment provides an additional support for our model.

 

Title:
Exclusively visual analysis of classroom group interactions
Authors:
Tucker, Laura; Scherr, Rachel E.; Zickler, Todd; Mazur, Eric
Publication:
Physical Review Physics Education Research, Volume 12, Issue 2, id.020142
Publication Date:
12/2016
Origin:
APS
Abstract Copyright:
2016: authors
DOI:
10.1103/PhysRevPhysEducRes.12.020142
Bibliographic Code:
2016PRSTP..12b0142T

Abstract

Large-scale audiovisual data that measure group learning are time consuming to collect and analyze. As an initial step towards scaling qualitative classroom observation, we qualitatively coded classroom video using an established coding scheme with and without its audio cues. We find that interrater reliability is as high when using visual data only—without audio—as when using both visual and audio data to code. Also, interrater reliability is high when comparing use of visual and audio data to visual-only data. We see a small bias to code interactions as group discussion when visual and audio data are used compared with video-only data. This work establishes that meaningful educational observation can be made through visual information alone. Further, it suggests that after initial work to create a coding scheme and validate it in each environment, computer-automated visual coding could drastically increase the breadth of qualitative studies and allow for meaningful educational analysis on a far greater scale.

 

Title:
Analysis of student engagement in an online annotation system in the context of a flipped introductory physics class
Authors:
Miller, Kelly; Zyto, Sacha; Karger, David; Yoo, Junehee; Mazur, Eric
Publication:
Physical Review Physics Education Research, Volume 12, Issue 2, id.020143
Publication Date:
12/2016
Origin:
AIP
Abstract Copyright:
2016: authors
DOI:
10.1103/PhysRevPhysEducRes.12.020143
Bibliographic Code:
2016PRSTP..12b0143M

Abstract

We discuss student participation in an online social annotation forum over two semesters of a flipped, introductory physics course at Harvard University. We find that students who engage in high-level discussion online, especially by providing answers to their peers' questions, make more gains in conceptual understanding than students who do not. This is true regardless of students' physics background. We find that we can steer online interaction towards more productive and engaging discussion by seeding the discussion and managing the size of the sections. Seeded sections produce higher quality annotations and a greater proportion of generative threads than unseeded sections. Larger sections produce longer threads; however, beyond a certain section size, the quality of the discussion decreases.

 

Title:
The novel metallic states of the cuprates: Topological Fermi liquids and strange metals
Authors:
Sachdev, Subir; Chowdhury, Debanjan
Publication:
Progress of Theoretical and Experimental Physics, Volume 2016, Issue 12, id.12C102 26 pp. (OUP Homepage)
Publication Date:
12/2016
Origin:
OUP
Keywords:
I45, I46, I64
Abstract Copyright:
The Author(s) 2016. Published by Oxford University Press on behalf of the Physical Society of Japan.
DOI:
10.1093/ptep/ptw110
Bibliographic Code:
2016PTEP.2016lC102S

Abstract

We review ideas on the nature of the metallic states of the hole-doped cuprate high temperature superconductors, with an emphasis on the connections between the Luttinger theorem for the size of the Fermi surface, topological quantum field theories (TQFTs), and critical theories involving changes in the size of the Fermi surface. We begin with the derivation of the Luttinger theorem for a Fermi liquid, using momentum balance during a process of flux insertion in a lattice electronic model with toroidal boundary conditions. We then review the TQFT of the ℤ spin liquid, and demonstrate its compatibility with the toroidal momentum balance argument. This discussion leads naturally to a simple construction of "topological" Fermi liquid states: the fractionalized Fermi liquid (FL*) and the algebraic charge liquid (ACL). We present arguments for a description of the pseudogap metal of the cuprates using ℤ-FL* or ℤ-ACL states with Ising-nematic order. These pseudogap metal states are also described as Higgs phases of a SU(2) gauge theory. The Higgs field represents local antiferromagnetism, but the Higgs-condensed phase does not have long-range antiferromagnetic order: the magnitude of the Higgs field determines the pseudogap, the reconstruction of the Fermi surface, and the Ising-nematic order. Finally, we discuss the route to the large Fermi surface Fermi liquid via the critical point where the Higgs condensate and Ising nematic order vanish, and the application of Higgs criticality to the strange metal.

 

Title:
Particle-Hole Symmetry in the Fermion-Chern-Simons and Dirac Descriptions of a Half-Filled Landau Level
Authors:
Wang, Chong; Cooper, Nigel R.; Halperin, Bertrand I.; Stern, Ady
Publication:
eprint arXiv:1701.00007
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Mesoscale and Nanoscale Physics
Comment:
21 pages, 1 figure
Bibliographic Code:
2017arXiv170100007W

Abstract

It is well known that there is a particle-hole symmetry for spin-polarized electrons with two-body interactions in a partially filled Landau level, which becomes exact in the limit where the cyclotron energy is large compared to the interaction strength, so one can ignore mixing between Landau levels. This symmetry is explicit in the description of a half-filled Landau level recently introduced by D. T. Son, using Dirac fermions, but it was thought to be absent in the older fermion-Chern-Simons approach, developed by Halperin, Lee, and Read and subsequent authors. We show here, however, that when properly evaluated, the Halperin, Lee, Read (HLR) theory gives results for long-wavelength low-energy physical properties, including the Hall conductance in the presence of impurities and the positions of minima in the magnetoroton spectra for fractional quantized Hall states close to half-filling, that are identical to predictions of the Dirac formulation. In fact, the HLR theory predicts an emergent particle-hole symmetry near half filling, even when the cyclotron energy is finite.


Title:
Flat Space Amplitudes and Conformal Symmetry of the Celestial Sphere
Authors:
Pasterski, Sabrina; Shao, Shu-Heng; Strominger, Andrew
Publication:
eprint arXiv:1701.00049
Publication Date:
12/2016
Origin:
ARXIV
Keywords:
High Energy Physics - Theory
Comment:
13 pages
Bibliographic Code:
2017arXiv170100049P

Abstract

The four-dimensional (4D) Lorentz group $SL(2,\mathbb{C})$ acts as the two-dimensional (2D) global conformal group on the celestial sphere at infinity where asymptotic 4D scattering states are specified. Consequent similarities of 4D flat space amplitudes and 2D correlators on the conformal sphere are obscured by the fact that the former are usually expressed in terms of asymptotic wavefunctions which transform simply under spacetime translations rather than the Lorentz $SL(2,\mathbb{C})$. In this paper we construct on-shell massive scalar wavefunctions in 4D Minkowski space that transform as $SL(2,\mathbb{C})$ conformal primaries. Scattering amplitudes of these wavefunctions are $SL(2,\mathbb{C})$ covariant by construction. For certain mass relations, we show explicitly that their three-point amplitude reduces to the known unique form of a 2D CFT primary three-point function and compute the coefficient. The computation proceeds naturally via Witten-like diagrams on a hyperbolic slicing of Minkowski space and has a holographic flavor.

 


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