Faculty Publications: July, 2016

Query Results from the Smithsonian/NASA Astrophysics Data System (ADS)

The following are Harvard Physics faculty members' publications, added to the ADS database last month. Please note that some publications which appeared in print last month may not be included in the database (and therefore may not appear on this list) until the following month.

Title:
The Glass Cage: How Our Computers are Changing Us
Authors:
Huth, John
Publication:
American Journal of Physics, Volume 84, Issue 7, p.565-566
Publication Date:
07/2016
Origin:
AIP
DOI:
10.1119/1.4946823
Bibliographic Code:
2016AmJPh..84..565H

Abstract

Not Available

 

Title:
BICEP2/Keck Array. VII. Matrix Based E/B Separation Applied to Bicep2 and the Keck Array
Authors:
BICEP2 Collaboration; Keck Array Collaboration; Ade, P. A. R.; Ahmed, Z.; Aikin, R. W.;... Dvorkin, C.;... Kovac, J. M.; ... and 57 coauthors
Publication:
The Astrophysical Journal, Volume 825, Issue 1, article id. 66, pp. (2016). (ApJ Homepage)
Publication Date:
07/2016
Origin:
IOP
Astronomy Keywords:
cosmic background radiation, cosmology: observations, gravitational waves, inflation, polarization
DOI:
10.3847/0004-637X/825/1/66
Bibliographic Code:
2016ApJ...825...66B

Abstract

A linear polarization field on the sphere can be uniquely decomposed into an E-mode and a B-mode component. These two components are analytically defined in terms of spin-2 spherical harmonics. Maps that contain filtered modes on a partial sky can also be decomposed into E-mode and B-mode components. However, the lack of full sky information prevents orthogonally separating these components using spherical harmonics. In this paper, we present a technique for decomposing an incomplete map into E and B-mode components using E and B eigenmodes of the pixel covariance in the observed map. This method is found to orthogonally define E and B in the presence of both partial sky coverage and spatial filtering. This method has been applied to the Bicep2 and the Keck Array maps and results in reducing E to B leakage from ΛCDM E-modes to a level corresponding to a tensor-to-scalar ratio of r\lt 1× {10}-4.

 

Title:
Localization and Broadband Follow-up of the Gravitational-wave Transient GW150914
Authors:
Abbott, B. P.; Abbott, R.; Abbott, T. D.;...
Publication:
The Astrophysical Journal Letters, Volume 826, Issue 1, article id. L13, pp. (2016). (ApJL Homepage)
Publication Date:
07/2016
Origin:
IOP
Astronomy Keywords:
gravitational waves, methods: observational
DOI:
10.3847/2041-8205/826/1/L13
Bibliographic Code:
2016ApJ...826L..13A

Abstract

A gravitational-wave (GW) transient was identified in data recorded by the Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) detectors on 2015 September 14. The event, initially designated G184098 and later given the name GW150914, is described in detail elsewhere. By prior arrangement, preliminary estimates of the time, significance, and sky location of the event were shared with 63 teams of observers covering radio, optical, near-infrared, X-ray, and gamma-ray wavelengths with ground- and space-based facilities. In this Letter we describe the low-latency analysis of the GW data and present the sky localization of the first observed compact binary merger. We summarize the follow-up observations reported by 25 teams via private Gamma-ray Coordinates Network circulars, giving an overview of the participating facilities, the GW sky localization coverage, the timeline, and depth of the observations. As this event turned out to be a binary black hole merger, there is little expectation of a detectable electromagnetic (EM) signature. Nevertheless, this first broadband campaign to search for a counterpart of an Advanced LIGO source represents a milestone and highlights the broad capabilities of the transient astronomy community and the observing strategies that have been developed to pursue neutron star binary merger events. Detailed investigations of the EM data and results of the EM follow-up campaign are being disseminated in papers by the individual teams.

 

Title:
Complementarity and Stability Conditions
Authors:
Georgi, Howard
Publication:
eprint arXiv:1607.00369
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
High Energy Physics - Phenomenology, High Energy Physics - Theory
Comment:
13 pages
Bibliographic Code:
2016arXiv160700369G

Abstract

We discuss the issue of complementarity between the confining phase and the Higgs phase for gauge theories in which there are no light particles below the scale of confinement or spontaneous symmetry breaking. We show with a number of examples that even though the low energy effective theories are the same (and trivial), we can sometimes argue that the two phases have different heavy stable particles and thus cannot be complementary. We suggest that such "stability conditions" can be a useful physical check for complementarity.

 

Title:
Dynamics of soft filaments that can stretch, shear, bend and twist
Authors:
Gazzola, Mattia; Dudte, Levi H.; McCormick, Andrew G.; Mahadevan, L.
Publication:
eprint arXiv:1607.00430
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Physics - Fluid Dynamics, Condensed Matter - Soft Condensed Matter
Bibliographic Code:
2016arXiv160700430G

Abstract

Soft slender structures are ubiquitous in natural and artificial systems and can be observed at scales that range from the nanometric to the kilometric, from polymers to space tethers. We present a general numerical approach to simulate the dynamics of filaments that, at every cross-section, can undergo all six possible modes of deformation, allowing the filament to bend, twist, shear and stretch, consistent with dynamics on the full Euclidean group SE(3). Additionally, we also account for the interaction of an active filament with itself and the environment via self-contact, surface friction and hydrodynamics. We examine the accuracy of our energy preserving and second order spatio-temporal method by means of a number of benchmark problems with known analytic solutions. Finally, we demonstrate the capabilities of our approach both on passive physical problems related to solenoid and plectoneme formation in twisted, stretched filaments, and active biophysical problems in the context of limbless locomotion on solid surfaces and in bulk liquids. All together, our approach allows for a broad computational generalization of available methods to study the dynamics of soft filaments.

 

Title:
A search for sterile neutrinos mixing with muon neutrinos in MINOS
Authors:
Adamson, P.; Anghel, I.; Aurisano, A.;... Feldman, G. J.; ; and 116 coauthors
Publication:
eprint arXiv:1607.01176
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
High Energy Physics - Experiment, High Energy Physics - Phenomenology
Comment:
Submitted to Phys. Rev. Lett.; 6 pages, 4 figures
Bibliographic Code:
2016arXiv160701176A

Abstract

We report results of a search for oscillations involving a light sterile neutrino over distances of 1.04 km and 735 km in a $\nu_{\mu}$-dominated beam with peak energy of 3 GeV. The data, from an exposure of $10.56\times 10^{20}$ protons-on-target, are analyzed using a phenomenological model with one sterile neutrino. We constrain the mixing parameters $\theta_{24}$ and $\Delta m^{2}_{41}$ and set limits on parameters of the four-dimensional PMNS matrix, $|U_{\mu 4}|^{2}$ and $|U_{\tau 4}|^{2}$, under the assumption that mixing between $\nu_{e}$ and $\nu_{s}$ is negligible ($|U_{e4}|^{2}=0$). No evidence for $\nu_{\mu} \to \nu_{s}$ transitions is found and we set a world-leading limit on $\theta_{24}$ for values of $\Delta m^{2}_{41} \lesssim 1 \mathrm{eV}^{2}$.

 

Title:
Limits on Active to Sterile Neutrino Oscillations from Disappearance Searches in the MINOS, Daya Bay, and Bugey-3 Experiments
Authors:
Bay, Daya; MINOS Collaborations; :; Adamson, P.; An, F. P.; Anghel, I.;... Feldman, G. J.; ... and 322 coauthors
Publication:
eprint arXiv:1607.01177
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
High Energy Physics - Experiment
Comment:
8 pages, 4 figures, to be submitted to Phys. Rev. Letters
Bibliographic Code:
2016arXiv160701177B

Abstract

Searches for a light sterile neutrino have been independently performed by the MINOS and the Daya Bay experiments using the muon (anti)neutrino and electron antineutrino disappearance channels, respectively. In this Letter, results from both experiments are combined with those from the Bugey-3 reactor neutrino experiment to constrain oscillations into light sterile neutrinos. The three experiments are sensitive to complementary regions of parameter space, enabling the combined analysis to probe regions allowed by the LSND and MiniBooNE experiments in a minimally extended four-neutrino flavor framework. Stringent limits on $\sin^2 2\theta_{\mu e}$ are set over six orders of magnitude in the sterile mass-squared splitting $\Delta m^2_{41}$. The sterile-neutrino mixing phase space allowed by the LSND and MiniBooNE experiments is excluded for $\Delta m^2_{41} < 0.8$ eV$^2$ at 95\% C.L.

 

Title:
A low-temperature external cavity diode laser for broad wavelength tuning
Authors:
Tobias, William G.; Rosenberg, Jason S.; Hutzler, Nicholas R.; Ni, Kang-Kuen
Publication:
eprint arXiv:1607.01347
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Physics - Atomic Physics, Physics - Chemical Physics, Physics - Instrumentation and Detectors
Comment:
6 pages, 6 figures
Bibliographic Code:
2016arXiv160701347T

Abstract

We report on the design and characterization of a low-temperature external cavity diode laser (ECDL) system for broad wavelength tuning. The performance achieved with multiple diode models addresses the scarcity of commercial red laser diodes below 633 nm, which is a wavelength range relevant to spectroscopy of many molecules and ions. Using a combination of multiple-stage thermoelectric cooling and water cooling, the operating temperature of a laser diode is lowered to -64{\deg}C, more than 85{\deg}C below the ambient temperature. The laser system integrates temperature and diffraction grating feedback tunability for coarse and fine wavelength adjustments, respectively. For two different diode models, single-mode operation was achieved with 38 mW output power at 616.8 nm and 69 mW at 622.6 nm, more than 15 nm below their ambient temperature free-running wavelengths. The ECDL design can be used for diodes of any available wavelength, allowing individual diodes to be tuned continuously over tens of nanometers and extending the wavelength coverage of commercial laser diodes.

 

Title:
An Underappreciated Radiation Hazard from High Voltage Electrodes in Vacuum
Authors:
West, Adam; Lasner, Zack; DeMille, David; West, Elizabeth; Panda, Cristian; Doyle, John; Gabrielse, Gerald; Kryskow, Adam; Mitchell, Corinne
Publication:
eprint arXiv:1607.01389
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Physics - Medical Physics, Physics - Instrumentation and Detectors
Comment:
Submitted to Health Physics
Bibliographic Code:
2016arXiv160701389W

Abstract

The use of high voltage (HV) electrodes in vacuum is commonplace in physics laboratories. In such systems, it has long been known that electron emission from an HV cathode can lead to bremsstrahlung X-rays; indeed, this is the basic principle behind the operation of standard X-ray sources. However, in laboratory setups where X-ray production is not the goal and no electron source is deliberately introduced, field-emitted electrons accelerated by HV can produce X-rays as an unintended hazardous byproduct. Both the level of hazard and the safe operating regimes for HV vacuum electrode systems are not widely appreciated, at least in university laboratories. A reinforced awareness of the radiation hazards associated with vacuum HV setups would be beneficial. We present a case study of a HV vacuum electrode device operated in a university atomic physics laboratory. We describe the characterisation of the observed X-ray radiation, its relation to the observed leakage current in the device, the steps taken to contain and mitigate the radiation hazard, and suggest safety guidelines.

 

Title:
Interferometric Approach to Probing Fast Scrambling
Authors:
Yao, Norman Y.; Grusdt, Fabian; Swingle, Brian; Lukin, Mikhail D.; Stamper-Kurn, Dan M.; Moore, Joel E.; Demler, Eugene A.
Publication:
eprint arXiv:1607.01801
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Quantum Physics, Condensed Matter - Disordered Systems and Neural Networks, Condensed Matter - Quantum Gases, Condensed Matter - Statistical Mechanics, High Energy Physics - Theory
Comment:
6 pages, 3 figures
Bibliographic Code:
2016arXiv160701801Y

Abstract

Out-of-time-order correlation functions provide a proxy for diagnosing chaos in quantum systems. We propose and analyze an interferometric scheme for their measurement, using only local quantum control and no reverse time evolution. Our approach utilizes a combination of Ramsey interferometry and the recently demonstrated ability to directly measure Renyi entropies. To implement our scheme, we present a pair of cold-atom-based experimental blueprints; moreover, we demonstrate that within these systems, one can naturally realize the transverse-field Sherrington-Kirkpatrick (TFSK) model, which exhibits certain similarities with fast scrambling black holes. We perform a detailed numerical study of scrambling in the TFSK model, observing an interesting interplay between the fast scrambling bound and the onset of spin-glass order.

 

Title:
Interacting in-plane molecular dipoles in a zig-zag chain
Authors:
Wang, Qingyang; Otterbach, Johannes; Yelin, Susanne F.
Publication:
eprint arXiv:1607.01851
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Quantum Gases, Quantum Physics
Comment:
11 pages, 6 figures
Bibliographic Code:
2016arXiv160701851W

Abstract

The system with externally polarized dipole molecules at half-filling moving along a one-dimensional zig-zag chain is studied theoretically, including the ground-state phase diagram. The dipoles are oriented in-plane. Together with the geometry of the chain this gives rise to a bond-alternating nearest neighbor interaction due to simultaneous attractive and repulsive interactions. Because of the quantum Zeno effect due to the reactive nature of molecules the system can be treated as hard-core. By tuning the ratio between the nearest-neighbor interaction and hopping, various phases can be accessed by controlling the polarization angle. In the ultra-strong coupling limit, the system simplifies to a frustrated extended axial Ising model. For the small coupling limit, qualitative discussion of the ordering behavior using effective field theory arguments is provided. We show that when chain angle is small, the system mostly exhibits BKT-type phase transitions, whereas large chain angle would drive the system into a gapped (Ising) dimerized phase, where the hopping strength is closely related to the orientation of dimerized pairs.

 

Title:
Anomalous conductances in an ultracold quantum wire
Authors:
Kanász-Nagy, Márton; Glazman, Leonid; Esslinger, Tilman; Demler, Eugene A.
Publication:
eprint arXiv:1607.02509
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Quantum Gases, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity, Physics - Atomic Physics
Comment:
5 pages, 4 figures. Supplementary Material available as an ancillary file
Bibliographic Code:
2016arXiv160702509K

Abstract

We analyze the recently measured anomalous transport properties of an ultracold gas through a ballistic constriction [S. Krinner et al., PNAS 201601812 (2016)]. The quantized conductance observed at weak interactions increases several-fold 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:
Mapping Reactive Flow Patterns in Monolithic Nanoporous Catalysts
Authors:
Falcucci, Giacomo; Succi, Sauro; Montessori, Andrea; Melchionna, Simone; Prestininzi, Pietro; Barroo, Cedric; Bell, David C.; Biener, Monika M.; Biener, Juergen; Zugic, Branko; Kaxiras, Efthimios
Publication:
eprint arXiv:1607.02874
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Physics - Fluid Dynamics, Condensed Matter - Materials Science, Physics - Chemical Physics, Physics - Computational Physics
Comment:
Microfluidics and Nanofluidics, 20(7), 1-13, 2016; doi:10.1007/s10404-016-1767-5
Bibliographic Code:
2016arXiv160702874F

Abstract

The development of high-efficiency porous catalyst membranes critically depends on our understanding of where the majority of the chemical conversions occur within the porous structure. This requires mapping of chemical reactions and mass transport inside the complex nano-scale architecture of porous catalyst membranes which is a multiscale problem in both the temporal and spatial domain. To address this problem, we developed a multi-scale mass transport computational framework based on the Lattice Boltzmann Method (LBM) that allows us to account for catalytic reactions at the gas-solid interface by introducing a new boundary condition. In good agreement with experiments, the simulations reveal that most catalytic reactions occur near the gas-flow facing side of the catalyst membrane if chemical reactions are fast compared to mass transport within the porous catalyst membrane.

 

Title:
Cold Matter Assembled Atom-by-Atom
Authors:
Endres, Manuel; Bernien, Hannes; Keesling, Alexander; Levine, Harry; Anschuetz, Eric R.; Krajenbrink, Alexandre; Senko, Crystal; Vuletic, Vladan; Greiner, Markus; Lukin, Mikhail D.
Publication:
eprint arXiv:1607.03044
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Quantum Physics, Condensed Matter - Quantum Gases, Physics - Atomic Physics
Comment:
12 pages, 9 figures, 3 movies as ancillary files
Bibliographic Code:
2016arXiv160703044E

Abstract

The realization of large-scale fully controllable quantum systems is an exciting frontier in modern physical science. We use atom-by-atom assembly to implement a novel platform for the deterministic preparation of regular arrays of individually controlled cold atoms. In our approach, a measurement and feedback procedure eliminates the entropy associated with probabilistic trap occupation and results in defect-free arrays of over 50 atoms in less than 400 ms. The technique is based on fast, real-time control of 100 optical tweezers, which we use to arrange atoms in desired geometric patterns and to maintain these configurations by replacing lost atoms with surplus atoms from a reservoir. This bottom-up approach enables controlled engineering of scalable many-body systems for quantum information processing, quantum simulations, and precision measurements.

 

Title:
Shear viscosity at the Ising-nematic quantum critical point in two dimensional metals
Authors:
Patel, Aavishkar A.; Eberlein, Andreas; Sachdev, Subir
Publication:
eprint arXiv:1607.03894
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons, High Energy Physics - Theory
Comment:
13 pages, 3 figures including supplementary material
Bibliographic Code:
2016arXiv160703894P

Abstract

In a strongly interacting quantum liquid without quasiparticles, general scaling arguments imply that the dimensionless ratio $(k_B /\hbar)\, \eta/s$, where $\eta$ is the shear viscosity and $s$ is the entropy density, is a universal number. We compute the shear viscosity of the Ising-nematic critical point of metals in spatial dimension $d=2$ by an expansion below $d=5/2$. The anisotropy associated with directions parallel and normal to the Fermi surface leads to a violation of the scaling expectations: $\eta$ scales in the same manner as a chiral conductivity, and the ratio $\eta/s$ diverges as $T^{-2/z}$, where $z$ is the dynamic critical exponent for fermionic excitations dispersing normal to the Fermi surface.

 

Title:
Optical Characterization of the BICEP3 CMB Polarimeter at the South Pole
Authors:
Karkare, K. S.; Ade, P. A. R.; Ahmed, Z.; Alexander, K. D.; Amiri, M.; Barkats, D.; Benton, S. J.; Bischoff, C. A.; Bock, J. J.; Boenish, H.; Bowens-Rubin, R.; Buder, I.; Bullock, E.; Buza, V.; Connors, J.; Filippini, J. P.; Fliescher, S. T.; Grayson, J. A.; Halpern, M.; Harrison, S. A.; Hilton, G. C.; Hristov, V. V.; Hui, H.; Irwin, K. D.; Kang, J. H.; Karpel, E.; Kefeli, S.; Kernasovskiy, S. A.; Kovac, J. M.; Kuo, C. L.; Leitch, E. M.; Lueker, M.; Megerian, K. G.; Monticue, V.; Namikawa, T.; Netterfield, C. B.; Nguyen, H. T.; O'Brient, R.; Ogburn, R. W., IV; Pryke, C.; Reintsema, C. D.; Richter, S.; St. Germaine, M. T.; Schwarz, R.; Sheehy, C. D.; Staniszewski, Z. K.; Steinbach, B.; Teply, G. P.; Thompson, K. L.; Tolan, J. E.; Tucker, C.; Turner, A. D.; Vieregg, A. G.; Wandui, A.; Weber, A.; Willmert, J.; Wong, C. L.; Wu, W. L. K.; Yoon, K. W.
Publication:
eprint arXiv:1607.04567
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics
Comment:
17 pages, 9 figures. Presented at SPIE Astronomical Telescopes and Instrumentation Conference 9914: Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VIII, June 2016
Bibliographic Code:
2016arXiv160704567K

Abstract

BICEP3 is a small-aperture refracting cosmic microwave background (CMB) telescope designed to make sensitive polarization maps in pursuit of a potential B-mode signal from inflationary gravitational waves. It is the latest in the BICEP/Keck Array series of CMB experiments at the South Pole, which has provided the most stringent constraints on inflation to date. For the 2016 observing season, BICEP3 was outfitted with a full suite of 2400 optically coupled detectors operating at 95 GHz. In these proceedings we report on the far field beam performance using calibration data taken during the 2015-2016 summer deployment season in situ with a thermal chopped source. We generate high-fidelity per-detector beam maps, show the array-averaged beam profile, and characterize the differential beam response between co-located, orthogonally polarized detectors which contributes to the leading instrumental systematic in pair differencing experiments. We find that the levels of differential pointing, beamwidth, and ellipticity are similar to or lower than those measured for BICEP2 and Keck Array. The magnitude and distribution of BICEP3's differential beam mismatch - and the level to which temperature-to-polarization leakage may be marginalized over or subtracted in analysis - will inform the design of next-generation CMB experiments with many thousands of detectors.

 

Title:
Inference of Unresolved Point Sources At High Galactic Latitudes Using Probabilistic Catalogs
Authors:
Daylan, Tansu; Portillo, Stephen K. N.; Finkbeiner, Douglas P.
Publication:
eprint arXiv:1607.04637
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Phenomenology
Bibliographic Code:
2016arXiv160704637D

Abstract

We construct a Bayesian framework to perform inference of dim or overlapping point sources. The method involves probabilistic cataloging, where samples are taken from the posterior probability distribution of catalogs consistent with an observed photon count map. By implementing across-model jumps between point source models of different dimensionality, we collect a representative ensemble of catalogs consistent with the image. In order to validate our method we sample random catalogs of the gamma-ray sky in the direction of the North Galactic Pole (NGP) by binning the data in energy and PSF (Point Spread Function) classes. Using three energy bins between $0.3 - 1$, $1 - 3$ and $3 - 10$ GeV, we identify $270\substack{+30 -10}$ point sources inside a $40^\circ \times 40^\circ$ region around the NGP above our point-source inclusion limit of $3 \times 10^{-11}$/cm$^2$/s/sr/GeV at the $1-3$ GeV energy bin. Most of these point sources are time-variable blazars. Modeling the flux distribution as a single power law, we infer the slope to be $-1.92\substack{+0.07 -0.05}$ and estimate the contribution of point sources (resolved and unresolved) to the total emission as $18\substack{+2 -2}$\%. Further analyses that rely on the ensemble of sample catalogs instead of only the most likely catalog, can perform reliable marginalization over uncertainties in the number as well as spatial and spectral properties of the point sources. This marginalization allows a robust test of whether the apparently isotropic emission in an image is due to unresolved point sources or of truly diffuse origin. With the increase in the availability of computational resources in the near future, probabilistic cataloging can potentially be applied to full sky datasets or optical images and replace the standard data reduction pipelines for crowded fields.

 

itle:
BICEP3 performance overview and planned Keck Array upgrade
Authors:
Grayson, J. A.; Ade, P. A. R.; Ahmed, Z.; Alexander, K. D.; Amiri, M.; Barkats, D.; Benton, S. J.; Bischoff, C. A.; Bock, J. J.; Boenish, H.; Bowens-Rubin, R.; Buder, I.; Bullock, E.; Buza, V.; Connors, J.; Filippini, J. P.; Fliescher, S.; Halpern, M.; Harrison, S.; Hilton, G. C.; Hristov, V. V.; Hui, H.; Irwin, K. D.; Kang, J.; Karkare, K. S.; Karpel, E.; Kefeli, S.; Kernasovskiy, S. A.; Kovac, J. M.; Kuo, C. L.; Leitch, E. M.; Lueker, M.; Megerian, K. G.; Monticue, V.; Namikawa, T.; Netterfield, C. B.; Nguyen, H. T.; O'Brient, R.; Ogburn, R. W., IV; Pryke, C.; Reintsema, C. D.; Richter, S.; Schwarz, R.; Sorensen, C.; Sheehy, C. D.; Staniszewski, Z. K.; Steinbach, B.; Teply, G. P.; Thompson, K. L.; Tolan, J. E.; Tucker, C.; Turner, A. D.; Vieregg, A. G.; Wandui, A.; Weber, A. C.; Wiebe, D. V.; Willmert, J.; Wu, W. L. K.; Yoon, K. W.
Publication:
eprint arXiv:1607.04668
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics
Comment:
17 pages, 6 figures. To be published in Proc. SPIE. Presented at SPIE Astronomical Telescopes and Instrumentation Conference 9914: Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VIII, June 2016
Bibliographic Code:
2016arXiv160704668G

Abstract

BICEP3 is a 520 mm aperture, compact two-lens refractor designed to observe the polarization of the cosmic microwave background (CMB) at 95 GHz. Its focal plane consists of modularized tiles of antenna-coupled transition edge sensors (TESs), similar to those used in BICEP2 and the Keck Array. The increased per-receiver optical throughput compared to BICEP2/Keck Array, due to both its faster f/1.7 optics and the larger aperture, more than doubles the combined mapping speed of the BICEP/Keck program. The BICEP3 receiver was recently upgraded to a full complement of 20 tiles of detectors (2560 TESs) and is now beginning its second year of observation (and first science season) at the South Pole. We report on its current performance and observing plans. Given its high per-receiver throughput while maintaining the advantages of a compact design, BICEP3-class receivers are ideally suited as building blocks for a 3rd-generation CMB experiment, consisting of multiple receivers spanning 35 GHz to 270 GHz with total detector count in the tens of thousands. We present plans for such an array, the new "BICEP Array" that will replace the Keck Array at the South Pole, including design optimization, frequency coverage, and deployment/observing strategies.

 

Title:
Superlattice-induced insulating states and valley-protected orbits in twisted bilayer graphene
Authors:
Cao, Y.; Luo, J. Y.; Fatemi, V.; Fang, S.; Sanchez-Yamagishi, J. D.; Watanabe, K.; Taniguchi, T.; Kaxiras, E.; Jarillo-Herrero, P.
Publication:
eprint arXiv:1607.05147
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Mesoscale and Nanoscale Physics
Comment:
5 pages, 4 figures
Bibliographic Code:
2016arXiv160705147C

Abstract

Twisted bilayer graphene (TwBLG) is one of the simplest van der Waals heterostructures, yet it yields a complex electronic system with intricate interplay between moir\'{e} physics and interlayer hybridization effects. We report on electronic transport measurements of high mobility small angle TwBLG devices showing clear evidence for insulating states at the superlattice band edges, with thermal activation gaps several times larger than theoretically predicted. Moreover, Shubnikov-de Haas oscillations and tight binding calculations reveal that the band structure consists of two intersecting Fermi contours whose crossing points are effectively unhybridized. We attribute this to exponentially suppressed interlayer hopping amplitudes for momentum transfers larger than the moir\'{e} wavevector.

 

Title:
Multitracing Anisotropic Non-Gaussianity with Galaxy Shapes
Authors:
Chisari, Nora Elisa; Dvorkin, Cora; Schmidt, Fabian; Spergel, David
Publication:
eprint arXiv:1607.05232
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Astrophysics of Galaxies
Comment:
11 pages, 4 figures
Bibliographic Code:
2016arXiv160705232C

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 multi-tracer 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, $A_2$, is forecast to be $\sigma(A_2)\approx 50$, $\sim 40\%$ 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:
Spectrum of conformal gauge theories on a torus
Authors:
Thomson, Alex; Sachdev, Subir
Publication:
eprint arXiv:1607.05279
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Statistical Mechanics, High Energy Physics - Theory
Comment:
33 pages
Bibliographic Code:
2016arXiv160705279T

Abstract

Many model quantum spin systems have been proposed to realize critical points or phases described by 2+1 dimensional conformal gauge theories. On a torus of size $L$ and modular parameter $\tau$, the energy levels of such gauge theories equal $(1/L)$ times universal functions of $\tau$. We compute the universal spectrum of QED$_3$, a U(1) gauge theory with $N_f$ two-component massless Dirac fermions, in the large $N_f$ limit. We also allow for a Chern-Simons term at level $k$, and show how the topological $k$-fold ground state degeneracy in the absence of fermions transforms into the universal spectrum in the presence of fermions; these computations are performed at fixed $N_f/k$ in the large $N_f$ limit.

 

Title:
A fractionalized Fermi liquid with bosonic chargons as a candidate for the pseudogap metal
Authors:
Chatterjee, Shubhayu; Sachdev, Subir
Publication:
eprint arXiv:1607.05727
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Superconductivity
Comment:
25 + 5 pages, 7 figures, 1 table
Bibliographic Code:
2016arXiv160705727C

Abstract

Doping a Mott-insulating $\mathbb{Z}_2$ spin liquid can lead to a fractionalized Fermi liquid (FL*). Such a phase has several favorable features that make it a candidate for the pseudogap metal for the underdoped cuprates. We focus on a particular, simple $\mathbb{Z}_2$-FL* state which can undergo a confinement transition to a spatially uniform superconductor which is smoothly connected to the `plain vanilla' BCS superconductor with $d$-wave pairing. Such a transition occurs by the condensation of bosonic particles carrying $+e$ charge but no spin (`chargons'). We show that modifying the dispersion of the bosonic chargons can lead to confinement transitions with charge density waves and pair density waves at the same wave-vector $\mathbf{K}$, co-existing with $d$-wave superconductivity. We also compute the evolution of the Hall number in the normal state during the transition from the plain vanilla FL* state to a Fermi liquid, and argue, following Coleman $\it{ et \, al.}$, that it exhibits a discontinuous jump near optimal doping. We note the distinction between these results and those obtained from models of the pseudogap with fermionic chargons.

 

Title:
Mutation at Expanding Front of Self-Replicating Colloidal Clusters
Authors:
Tanaka, Hidenori; Zeravcic, Zorana; Brenner, Michael P.
Publication:
eprint arXiv:1607.05802
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Soft Condensed Matter, Physics - Biological Physics
Bibliographic Code:
2016arXiv160705802T

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:
Photon Emission Near Extreme Kerr Black Holes
Authors:
Porfyriadis, Achilleas P.; Shi, Yichen; Strominger, Andrew
Publication:
eprint arXiv:1607.06028
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
General Relativity and Quantum Cosmology, Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Theory
Comment:
11 pages
Bibliographic Code:
2016arXiv160706028P

Abstract

Ongoing astronomical efforts extract physical properties of black holes from electromagnetic emissions in their near-vicinity. This requires finding the null geodesics which extend from the near-horizon region out to a distant observatory. In general these can only be found numerically. In this paper, for the interesting special case of extremally spinning Kerr black holes, we use an emergent near-horizon conformal symmetry to find near-superradiant geodesics analytically.

 

Title:
Fermi surface reconstruction and drop of Hall number due to spiral antiferromagnetism in high-$T_c$ cuprates
Authors:
Eberlein, Andreas; Metzner, Walter; Sachdev, Subir; Yamase, Hiroyuki
Publication:
eprint arXiv:1607.06087
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Superconductivity
Comment:
6 pages, 4 figures
Bibliographic Code:
2016arXiv160706087E

Abstract

We show that a Fermi surface reconstruction due to spiral antiferromagnetic order may explain the rapid change in the Hall number as recently observed near optimal doping in cuprate superconductors [Badoux~\textit{et. al.}, Nature \textbf{531}, 210 (2016)]. The single-particle spectral function in the spiral state exhibits hole pockets which look like Fermi arcs due to a strong momentum dependence of the spectral weight. Adding charge-density wave order further reduces the Fermi surface to a single electron pocket. We propose quantum oscillation measurements to distinguish between commensurate and spiral antiferromagnetic order.

 

Title:
A Synoptic Map of Halo Substructures from the Pan-STARRS1 3\pi\ 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; Martinez-Delgado, David; Sesar, Branimir; Wyse, Rosemary F. G.; Burgett, William S.; Chambers, Kenneth C.; Draper, Peter W.; Hodapp, Klaus W.; Kudritzki, Rolf-Peter; Magnier, Eugene A.; Metcalfe, Nigel; Wainscoat, Richard J.; Waters, Christopher
Publication:
eprint arXiv:1607.06088
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Astrophysics - Astrophysics of Galaxies
Comment:
11 pages, 6 figures. Submitted to MNRAS. A high-resolution version of Figure 1 is available at http://www.roe.ac.uk/~ejb/files/3maps.eps.gz, while full sky colour maps in various projections are provided at http://www.roe.ac.uk/~ejb/streams.html
Bibliographic Code:
2016arXiv160706088B

Abstract

We present a panoramic map of the entire Milky Way halo north of dec~-30 degrees (~30,000 deg^2), constructed by applying the matched-filter technique to the Pan-STARRS1 3Pi Survey dataset. 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 datasets 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 degrees), 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 3Pi data is currently too shallow to determine their properties or produce convincing CMDs. 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:
BICEP3 focal plane design and detector performance
Authors:
Hui, H.; Ade, P. A. R.; Ahmed, Z.; Alexander, K. D.; Amiri, M.; Barkats, D.; Benton, S. J.; Bischoff, C. A.; Bock, J. J.; Boenish, H.; Bowens-Rubin, R.; Buder, I.; Bullock, E.; Buza, V.; Connors, J.; Filippini, J. P.; Fliescher, S.; Grayson, J. A.; Halpern, M.; Harrison, S.; Hilton, G. C.; Hristov, V. V.; Irwin, K. D.; Kang, J.; Karkare, K. S.; Karpel, E.; Kefeli, S.; Kernasovskiy, S. A.; Kovac, J. M.; Kuo, C. L.; Leitch, E. M.; Lueker, M.; Megerian, K. G.; Monticue, V.; Namikawa, T.; Netterfield, C. B.; Nguyen, H. T.; O'Brient, R.; Ogburn, R. W., IV; Pryke, C.; Reintsema, C. D.; Richter, S.; Schwarz, R.; Sorensen, C.; Sheehy, C. D.; Staniszewski, Z. K.; Steinbach, B.; Teply, G. P.; Thompson, K. L.; Tolan, J. E.; Tucker, C.; Turner, A. D.; Vieregg, A. G.; Wandui, A.; Weber, A. C.; Wiebe, D. V.; Willmert, J.; Wu, W. L. K.; Yoon, K. W.
Publication:
eprint arXiv:1607.06861
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Astrophysics - Instrumentation and Methods for Astrophysics
Comment:
11 pages, 10 figures. To be published in Proc. SPIE. Presented at SPIE Astronomical Telescopes and Instrumentation Conference 9914: Millimeter, Submillimeter, and Far-Infrared Detectors and Instrumentation for Astronomy VIII, June 2016
Bibliographic Code:
2016arXiv160706861H

Abstract

BICEP3, the latest telescope in the BICEP/Keck program, started science observations in March 2016. It is a 550mm aperture refractive telescope observing the polarization of the cosmic microwave background at 95 GHz. We show the focal plane design and detector performance, including spectral response, optical efficiency and preliminary sensitivity of the upgraded BICEP3. We demonstrate 9.72$\mu$K$\sqrt{\textrm{s}}$ noise performance of the BICEP3 receiver.

 

Title:
The Relationship Between Local Structure and Relaxation in Out-of-Equilibrium Glassy Systems
Authors:
Schoenholz, Samuel S.; Cubuk, Ekin D.; Kaxiras, Efthimios; Liu, Andrea J.
Publication:
eprint arXiv:1607.06969
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Soft Condensed Matter
Bibliographic Code:
2016arXiv160706969S

Abstract

The dynamical glass transition is typically taken to be the temperature at which a glassy liquid is no longer able to equilibrate on experimental timescales. Consequently, the physical properties of these systems just above or below the dynamical glass transition, such as viscosity, can change by many orders of magnitude over long periods of time following external perturbation. During this progress towards equilibrium, glassy systems exhibit a history dependence that has complicated their study. In previous work, we bridged the gap between structure and dynamics in glassy liquids above their dynamical glass transition temperatures by introducing a scalar field called "softness", a quantity obtained using machine learning methods. Softness is designed to capture the hidden patterns in relative particle positions that correlate strongly with dynamical rearrangements of particle positions. Here we show that the out-of-equilibrium behavior of a model glassforming system can be understood in terms of softness. To do this we first demonstrate that the evolution of behavior following a temperature quench is a primarily structural phenomenon: the structure changes considerably, but the relationship between structure and dynamics remains invariant. We then show that the history-dependent relaxation time can be robustly computed from structure as quantified by softness. Together, these results motivate the use of softness to characterize the history dependence of glasses.

 

Title:
Contact-line pinning controls how quickly colloidal particles equilibrate with liquid interfaces
Authors:
Wang, Anna; McGorty, Ryan; Kaz, David M.; Manoharan, Vinothan N.
Publication:
eprint arXiv:1607.08154
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Soft Condensed Matter
Comment:
24 pages, 7 figures
Bibliographic Code:
2016arXiv160708154W

Abstract

Previous experiments have shown that spherical colloidal particles relax to equilibrium slowly after they adsorb to a liquid-liquid interface, despite the large interfacial energy gradient driving the adsorption. The slow relaxation has been explained in terms of transient pinning and depinning of the contact line on the surface of the particles. However, the nature of the pinning sites has not been investigated in detail. We use digital holographic microscopy to track a variety of colloidal spheres---inorganic and organic, charge-stabilized and sterically stabilized, aqueous and non-aqueous---as they breach liquid interfaces. We find that nearly all of these particles relax logarithmically in time over timescales much larger than those expected from viscous dissipation alone. By comparing our results to theoretical models of the pinning dynamics, we infer the area per defect to be on the order of a few square nanometers for each of the colloids we examine, whereas the energy per defect can vary from a few $kT$ for non-aqueous and inorganic spheres to tens of $kT$ for aqueous polymer particles. The results suggest that the likely pinning sites are topographical features inherent to colloidal particles---surface roughness in the case of silica particles and grafted polymer "hairs" in the case of polymer particles. We conclude that the slow relaxation must be taken into account in experiments and applications, such as Pickering emulsions, that involve colloids attaching to interfaces. The effect is particularly important for aqueous polymer particles, which pin the contact line strongly.

 

Title:
Effects of contact-line pinning on the adsorption of nonspherical colloids at liquid interfaces
Authors:
Wang, Anna; Rogers, W. Benjamin; Manoharan, Vinothan N.
Publication:
eprint arXiv:1607.08167
Publication Date:
07/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Soft Condensed Matter
Comment:
15 pages, 5 figures, 1 movie
Bibliographic Code:
2016arXiv160708167W

Abstract

The effects of contact-line pinning are well-known in macroscopic systems, but are only just beginning to be explored at the microscale in colloidal suspensions. We use digital holography to capture the fast three-dimensional dynamics of micrometer-sized ellipsoids breaching an oil-water interface. We find that the particle angle varies approximately linearly with the height, in contrast to results from simulations based on minimization of the interfacial energy. Using a simple model of the motion of the contact line, we show that the observed coupling between translational and rotational degrees of freedom is likely due to contact-line pinning. We conclude that the dynamics of colloidal particles adsorbing to a liquid interface are not determined by interfacial minimization and viscous dissipation alone; contact-line pinning dictates both the timescale and pathway to equilibrium.

 

Title:
Heterotic String Compactification and New Vector Bundles
Authors:
Lin, Hai; Wu, Baosen; Yau, Shing-Tung
Publication:
Communications in Mathematical Physics, Volume 345, Issue 2, pp.457-475
Publication Date:
07/2016
Origin:
SPRINGER
Abstract Copyright:
(c) 2016: Springer-Verlag Berlin Heidelberg
DOI:
10.1007/s00220-016-2679-7
Bibliographic Code:
2016CMaPh.345..457L

Abstract

We propose a construction of Kähler and non-Kähler Calabi-Yau manifolds by branched double covers of twistor spaces. In this construction we use the twistor spaces of four-manifolds with self-dual conformal structures, with the examples of connected sum of n {mathbb{P}2}s. We also construct K3-fibered Calabi-Yau manifolds from the branched double covers of the blow-ups of the twistor spaces. These manifolds can be used in heterotic string compactifications to four dimensions. We also construct stable and polystable vector bundles. Some classes of these vector bundles can give rise to supersymmetric grand unified models with three generations of quarks and leptons in four dimensions.

 

Title:
Measurement of event-shape observables in Z → ℓ+- events in pp collisions at √{s}=7 {TeV} with the ATLAS detector at the LHC
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2863 coauthors
Publication:
The European Physical Journal C, Volume 76, Issue 7, article id. #375, 40 pp. (EPJC Homepage)
Publication Date:
07/2016
Origin:
SPRINGER
Abstract Copyright:
(c) 2016: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-016-4176-8
Bibliographic Code:
2016EPJC...76..375A

Abstract

Event-shape observables measured using charged particles in inclusive Z-boson events are presented, using the electron and muon decay modes of the Z bosons. The measurements are based on an integrated luminosity of 1.1 fb^{-1} of proton-proton collisions recorded by the ATLAS detector at the LHC at a centre-of-mass energy √{s}=7 {TeV}. Charged-particle distributions, excluding the lepton-antilepton pair from the Z-boson decay, are measured in different ranges of transverse momentum of the Z boson. Distributions include multiplicity, scalar sum of transverse momenta, beam thrust, transverse thrust, spherocity, and F-parameter, which are in particular sensitive to properties of the underlying event at small values of the Z-boson transverse momentum. The measured observables are compared with predictions from P ythia 8, S herpa, and H erwig 7. Typically, all three Monte Carlo generators provide predictions that are in better agreement with the data at high Z-boson transverse momenta than at low Z-boson transverse momenta, and for the observables that are less sensitive to the number of charged particles in the event.

 

Title:
Search for squarks and gluinos in final states with jets and missing transverse momentum at √{s} =13 {TeV}with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2847 coauthors
Publication:
The European Physical Journal C, Volume 76, Issue 7, article id. #392, 29 pp. (EPJC Homepage)
Publication Date:
07/2016
Origin:
SPRINGER
Abstract Copyright:
(c) 2016: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-016-4184-8
Bibliographic Code:
2016EPJC...76..392A

Abstract

A search for squarks and gluinos in final states containing hadronic jets, missing transverse momentum but no electrons or muons is presented. The data were recorded in 2015 by the ATLAS experiment in √{s}=13 {TeV} proton-proton collisions at the Large Hadron Collider. No excess above the Standard Model background expectation was observed in 3.2 fb^{-1} of analyzed data. Results are interpreted within simplified models that assume R-parity is conserved and the neutralino is the lightest supersymmetric particle. An exclusion limit at the 95 % confidence level on the mass of the gluino is set at 1.51 {TeV} for a simplified model incorporating only a gluino octet and the lightest neutralino, assuming the lightest neutralino is massless. For a simplified model involving the strong production of mass-degenerate first- and second-generation squarks, squark masses below 1.03 {TeV} are excluded for a massless lightest neutralino. These limits substantially extend the region of supersymmetric parameter space excluded by previous measurements with the ATLAS detector.

 

Title:
Stealth Supersymmetry simplified
Authors:
Fan, JiJi; Krall, Rebecca; Pinner, David; Reece, Matthew; Ruderman, Joshua T.
Publication:
Journal of High Energy Physics, Volume 2016, Issue 7, article id. #16, 36 pp.
Publication Date:
07/2016
Origin:
SPRINGER
Keywords:
Supersymmetry Phenomenology
Abstract Copyright:
(c) 2016: The Author(s)
DOI:
10.1007/JHEP07(2016)016
Bibliographic Code:
2016JHEP...07..016F

Abstract

In Stealth Supersymmetry, bounds on superpartners from direct searches can be notably weaker than in standard supersymmetric scenarios, due to suppressed missing energy. We present a set of simplified models of Stealth Supersymmetry that motivate 13 TeV LHC searches. We focus on simplified models within the Natural Supersymmetry framework, in which the gluino, stop, and Higgsino are assumed to be lighter than other superpartners. Our simplified models exhibit novel decay patterns that differ significantly from topologies of the Minimal Supersymmetric Standard Model, with and without R-parity. We determine limits on stops and gluinos from searches at the 8 TeV LHC. Existing searches constitute a powerful probe of Stealth Supersymmetry gluinos with certain topologies. However, we identify simplified models where the gluino can be considerably lighter than 1 TeV. Stops are significantly less constrained in Stealth Supersymmetry than the MSSM, and we have identified novel stop decay topologies that are completely unconstrained by existing LHC searches.

 

Title:
Radiation pressure force from optical cycling on a polyatomic molecule
Authors:
Kozyryev, Ivan; Baum, Louis; Matsuda, Kyle; Hemmerling, Boerge; Doyle, John M.
Publication:
Journal of Physics B: Atomic, Molecular, and Optical Physics, Volume 49, Issue 13, article id. 134002 (2016).
Publication Date:
07/2016
Origin:
IOP
DOI:
10.1088/0953-4075/49/13/134002
Bibliographic Code:
2016JPhB...49m4002K

Abstract

We demonstrate multiple photon cycling and radiative force deflection on the triatomic free radical strontium monohydroxide (SrOH). Optical cycling is achieved on SrOH in a cryogenic buffer-gas beam by employing the rotationally closed P(N\prime\prime =1) branch of the vibronic transition {\tilde{X}}2{{{Σ }}}+(000)≤ftrightarrow {\tilde{A}}2{{{\Pi }}}1/2(000). A single repumping laser excites the Sr–O stretching vibrational mode, and photon cycling of the molecule deflects the SrOH beam by an angle of 0.2^\circ via scattering of ∼100 photons per molecule. This approach can be used for direct laser cooling of SrOH and more complex, isoelectronic species.

 

Title:
A search for an excited muon decaying to a muon and two jets in pp collisions at \sqrt{s}\;=\;8\;{\rm{TeV}} with the ATLAS detector
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2822 coauthors
Publication:
New Journal of Physics, Volume 18, Issue 7, article id. 073021 (2016).
Publication Date:
07/2016
Origin:
IOP
DOI:
10.1088/1367-2630/18/7/073021
Bibliographic Code:
2016NJPh...18g3021A

Abstract

A new search signature for excited leptons is explored. Excited muons are sought in the channel {pp}\to μ {μ }* \to μ μ
{{jet}} {{jet}}, assuming both the production and decay occur via a contact interaction. The analysis is based on 20.3 fb‑1 of pp collision data at a centre-of-mass energy of \sqrt{s} = 8 {{TeV}} taken with the ATLAS detector at the large hadron collider. No evidence of excited muons is found, and limits are set at the 95% confidence level on the cross section times branching ratio as a function of the excited-muon mass {m}* }. For {m}* } between 1.3 and 3.0 TeV, the upper limit on σ B({μ }* \to μ q\bar{q}) is between 0.6 and 1 fb. Limits on σ B are converted to lower bounds on the compositeness scale Λ. In the limiting case {{Λ }}={m}* }, excited muons with a mass below 2.8 TeV are excluded. With the same model assumptions, these limits at larger {μ }* masses improve upon previous limits from traditional searches based on the gauge-mediated decay {μ }* \to μ γ.

 

Title:
Charged-particle distributions in √{ s} = 13 TeVpp interactions measured with the ATLAS detector at the LHC
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2864 coauthors
Publication:
Physics Letters B, Volume 758, p. 67-88.
Publication Date:
07/2016
Origin:
ELSEVIER
Abstract Copyright:
(c) 2016 CERN for the benefit of the ATLAS Collaboration
DOI:
10.1016/j.physletb.2016.04.050
Bibliographic Code:
2016PhLB..758...67A

Abstract

Charged-particle distributions are measured in proton-proton collisions at a centre-of-mass energy of 13 TeV, using a data sample of nearly 9 million events, corresponding to an integrated luminosity of 170 μb-1, recorded by the ATLAS detector during a special Large Hadron Collider fill. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the dependence of the mean transverse momentum on the charged-particle multiplicity are presented. The measurements are performed with charged particles with transverse momentum greater than 500 MeV and absolute pseudorapidity less than 2.5, in events with at least one charged particle satisfying these kinematic requirements. Additional measurements in a reduced phase space with absolute pseudorapidity less than 0.8 are also presented, in order to compare with other experiments. The results are corrected for detector effects, presented as particle-level distributions and are compared to the predictions of various Monte Carlo event generators.

 

Title:
Search for single production of a vector-like quark via a heavy gluon in the 4b final state with the ATLAS detector in pp collisions at √{ s} = 8 TeV
Authors:
Aad, G.; Abbott, B.; Abdallah, J.; ;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2839 coauthors
Publication:
Physics Letters B, Volume 758, p. 249-268.
Publication Date:
07/2016
Origin:
ELSEVIER
Abstract Copyright:
(c) 2016 Elsevier Science B.V. All rights reserved.
DOI:
10.1016/j.physletb.2016.04.061
Bibliographic Code:
2016PhLB..758..249A

Abstract

A search is performed for the process pp →G* →BH b bar /BbarH b → Hb b bar → b b bar b b bar , predicted in composite Higgs scenarios, where G* is a heavy colour octet vector resonance and BH a vector-like quark of charge - 1 / 3. The data were obtained from pp collisions at a centre-of-mass energy of 8 TeV corresponding to an integrated luminosity of 19.5 fb-1, recorded by the ATLAS detector at the LHC. The largest background, multijet production, is estimated using a data-driven method. No significant excess of events with respect to Standard Model predictions is observed, and upper limits on the production cross section times branching ratio are set. Comparisons to the predictions from a specific benchmark model are made, resulting in lower mass limits in the two-dimensional mass plane of mG* vs. mBH.

 

Title:
Superconductivity from a confinement transition out of a fractionalized Fermi liquid with Z2 topological and Ising-nematic orders
Authors:
Chatterjee, Shubhayu; Qi, Yang; Sachdev, Subir; Steinberg, Julia
Publication:
Physical Review B, Volume 94, Issue 2, id.024502 (PhRvB Homepage)
Publication Date:
07/2016
Origin:
APS
Abstract Copyright:
2016: American Physical Society
DOI:
10.1103/PhysRevB.94.024502
Bibliographic Code:
2016PhRvB..94b4502C

Abstract

The Schwinger boson theory of the frustrated square lattice antiferromagnet yields a stable, gapped Z2 spin liquid ground state with time-reversal symmetry, incommensurate spin correlations, and long-range Ising-nematic order. We obtain an equivalent description of this state using fermionic spinons (the fermionic spinons can be considered to be bound states of the bosonic spinons and the visons). Upon doping, the Z2 spin liquid can lead to a fractionalized Fermi liquid (FL*) with small Fermi pockets of electronlike quasiparticles, while preserving the Z2 topological and Ising-nematic orders. We describe a Higgs transition out of this deconfined metallic state into a confining superconducting state which is almost always of the Fulde-Ferrell-Larkin-Ovchinnikov type, with spatial modulation of the superconducting order.

 

Title:
Numerical study of fermion and boson models with infinite-range random interactions
Authors:
Fu, Wenbo; Sachdev, Subir
Publication:
Physical Review B, Volume 94, Issue 3, id.035135 (PhRvB Homepage)
Publication Date:
07/2016
Origin:
APS
Abstract Copyright:
2016: American Physical Society
DOI:
10.1103/PhysRevB.94.035135
Bibliographic Code:
2016PhRvB..94c5135F

Abstract

We present numerical studies of fermion and boson models with random all-to-all interactions (the Sachdev-Ye-Kitaev models). The high-temperature expansion and exact diagonalization of the N -site fermion model are used to compute the entropy density: our results are consistent with the numerical solution of N =∞ saddle-point equations, and the presence of a nonzero entropy density in the limit of vanishing temperature. The exact-diagonalization results for the fermion Green's function also appear to converge well to the N =∞ solution. For the hard-core boson model, the exact-diagonalization study indicates spin-glass order. Some results on the entanglement entropy and the out-of-time-order correlators are also presented.

 

Title:
Optically Controlled Oscillators in an Engineered Bioelectric Tissue
Authors:
McNamara, Harold M.; Zhang, Hongkang; Werley, Christopher A.; Cohen, Adam E.
Publication:
Physical Review X, Volume 6, Issue 3, id.031001
Publication Date:
07/2016
Origin:
APS
Abstract Copyright:
2016: authors
DOI:
10.1103/PhysRevX.6.031001
Bibliographic Code:
2016PhRvX...6c1001M

Abstract

Complex electrical dynamics in excitable tissues occur throughout biology, but the roles of individual ion channels can be difficult to determine due to the complex nonlinear interactions in native tissue. Here, we ask whether we can engineer a tissue capable of basic information storage and processing, where all functional components are known and well understood. We develop a cell line with four transgenic components: two to enable collective propagation of electrical waves and two to enable optical perturbation and optical readout of membrane potential. We pattern the cell growth to define simple cellular ring oscillators that run stably for >2 h (˜104 cycles ) and that can store data encoded in the direction of electrical circulation. Using patterned optogenetic stimulation, we probe the biophysical attributes of this synthetic excitable tissue in detail, including dispersion relations, curvature-dependent wave front propagation, electrotonic coupling, and boundary effects. We then apply the biophysical characterization to develop an optically reconfigurable bioelectric oscillator. These results demonstrate the feasibility of engineering bioelectric tissues capable of complex information processing with optical input and output.

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