Faculty Publications: September, 2016

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

 go to Most Recent Faculty Publications

Title:
Molecular beam epitaxial growth and electronic transport properties of high quality topological insulator Bi2Se3 thin films on hexagonal boron nitride
Authors:
Park, Joon Young; Lee, Gil-Ho; Jo, Janghyun; Cheng, Austin K.; Yoon, Hosang; Watanabe, Kenji; Taniguchi, Takashi; Kim, Miyoung; Kim, Philip; Yi, Gyu-Chul
Publication:
2D Materials, Volume 3, Issue 3, article id. 035029 (2016). (IOP Homepage)
Publication Date:
09/2016
Origin:
IOP
DOI:
10.1088/2053-1583/3/3/035029
Bibliographic Code:
2016TDM.....3c5029P

Abstract

We report the molecular beam epitaxial growth and characterization of high quality topological insulator Bi2Se3 thin films on hexagonal boron nitride (h-BN). A two-step growth was developed, enhancing both the surface coverage and crystallinity of the films on h-BN. High-resolution transmission electron microscopy study showed an atomically abrupt and epitaxial interface formation between the h-BN substrate and Bi2Se3. We performed gate tuned magnetotransport characterizations of the device fabricated on the thin film and confirmed a high mobility surface state at the Bi2Se3/h-BN interface. The Berry phase obtained from Shubnikov-de Haas oscillations suggested this interfacial electronic state is a topologically protected Dirac state.

 

Title:
Two-dimensional van der Waals materials
Authors:
Ajayan, Pulickel; Kim, Philip; Banerjee, Kaustav
Publication:
Physics Today, vol. 69, issue 9, pp. 38-44
Publication Date:
09/2016
Origin:
CROSSREF
DOI:
10.1063/PT.3.3297
Bibliographic Code:
2016PhT....69i..38A

Abstract

Not Available

 

Title:
Search for heavy long-lived charged R-hadrons with the ATLAS detector in 3.2 fb-1 of proton-proton collision data at √{ s} = 13 TeV
Authors:
Aaboud, M.; Aad, G.; Abbott, B.;
Publication:
Physics Letters B, Volume 760, p. 647-665.
Publication Date:
09/2016
Origin:
ELSEVIER
Abstract Copyright:
(c) 2016 Elsevier Science B.V. All rights reserved.
DOI:
10.1016/j.physletb.2016.07.042
Bibliographic Code:
2016PhLB..760..647A

Abstract

A search for heavy long-lived charged R-hadrons is reported using a data sample corresponding to 3.2 fb-1 of proton-proton collisions at √{ s} = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider at CERN. The search is based on observables related to large ionisation losses and slow propagation velocities, which are signatures of heavy charged particles travelling significantly slower than the speed of light. No significant deviations from the expected background are observed. Upper limits at 95% confidence level are provided on the production cross section of long-lived R-hadrons in the mass range from 600 GeV to 2000 GeV and gluino, bottom and top squark masses are excluded up to 1580 GeV, 805 GeV and 890 GeV, respectively.

 

 

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:
Physical Review Letters, Volume 117, Issue 11, id.116804 (PhRvL Homepage)
Publication Date:
09/2016
Origin:
APS
Abstract Copyright:
2016: American Physical Society
DOI:
10.1103/PhysRevLett.117.116804
Bibliographic Code:
2016PhRvL.117k6804C

Abstract

Twisted bilayer graphene (TBLG) is one of the simplest van der Waals heterostructures, yet it yields a complex electronic system with intricate interplay between moiré physics and interlayer hybridization effects. We report on electronic transport measurements of high mobility small angle TBLG 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 moiré wave vector.

 

Title:
Water retention against drying with soft-particle suspensions in porous media
Authors:
Keita, E.; Kodger, T. E.; Faure, P.; Rodts, S.; Weitz, D. A.; Coussot, P.
Publication:
Physical Review E, Volume 94, Issue 3, id.033104 (PhRvE Homepage)
Publication Date:
09/2016
Origin:
APS
Abstract Copyright:
2016: American Physical Society
DOI:
10.1103/PhysRevE.94.033104
Bibliographic Code:
2016PhRvE..94c3104K

Abstract

Polymers suspended in granular packings have a significant impact on water retention, which is important for soil irrigation and the curing of building materials. Whereas the drying rate remains constant during a long period for pure water due to capillary flow providing liquid water to the evaporating surface, we show that it is not the case for a suspension made of soft polymeric particles called microgels: The drying rate decreases immediately and significantly. By measuring the spatial water saturation and concentration of suspended particles with magnetic resonance imaging, we can explain these original trends and model the process. In low-viscosity fluids, the accumulation of particles at the free surface induces a recession of the air-liquid interface. A simple model, assuming particle transport and accumulation below the sample free surface, is able to reproduce our observations without any fitting parameters. The high viscosity of the microgel suspension inhibits flow towards the free surface and a drying front appears. We show that water vapor diffusion over a defined and increasing length sets the drying rate. These results and model allow for better controlling the drying and water retention in granular porous materials.

 

Title:
Plastic deformation of tubular crystals by dislocation glide
Authors:
Beller, Daniel A.; Nelson, David R.
Publication:
Physical Review E, Volume 94, Issue 3, id.033004 (PhRvE Homepage)
Publication Date:
09/2016
Origin:
APS
Abstract Copyright:
2016: American Physical Society
DOI:
10.1103/PhysRevE.94.033004
Bibliographic Code:
2016PhRvE..94c3004B

Abstract

Tubular crystals, two-dimensional lattices wrapped into cylindrical topologies, arise in many contexts, including botany and biofilaments, and in physical systems such as carbon nanotubes. The geometrical principles of botanical phyllotaxis, describing the spiral packings on cylinders commonly found in nature, have found application in all these systems. Several recent studies have examined defects in tubular crystals associated with crystalline packings that must accommodate a fixed tube radius. Here we study the mechanics of tubular crystals with variable tube radius, with dislocations interposed between regions of different phyllotactic packings. Unbinding and separation of dislocation pairs with equal and opposite Burgers vectors allow the growth of one phyllotactic domain at the expense of another. In particular, glide separation of dislocations offers a low-energy mode for plastic deformations of solid tubes in response to external stresses, reconfiguring the lattice step by step. Through theory and simulation, we examine how the tube's radius and helicity affects, and is in turn altered by, the mechanics of dislocation glide. We also discuss how a sufficiently strong bending rigidity can alter or arrest the deformations of tubes with small radii.

 

Title:
Search for top squarks in final states with one isolated lepton, jets, and missing transverse momentum in √{s }=13 TeV p p collisions with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2855 coauthors; Atlas Collaboration
Publication:
Physical Review D, Volume 94, Issue 5, id.052009 (PhRvD Homepage)
Publication Date:
09/2016
Origin:
APS
Abstract Copyright:
2016: CERN
DOI:
10.1103/PhysRevD.94.052009
Bibliographic Code:
2016PhRvD..94e2009A

Abstract

The results of a search for the top squark, the supersymmetric partner of the top quark, in final states with one isolated electron or muon, jets, and missing transverse momentum are reported. The search uses the 2015 LHC p p collision data at a center-of-mass energy of √{s }=13 TeV recorded by the ATLAS detector and corresponding to an integrated luminosity of 3.2 fb-1 . The analysis targets two types of signal models: gluino-mediated pair production of top squarks with a nearly mass-degenerate top squark and neutralino and direct pair production of top squarks, decaying to the top quark and the lightest neutralino. The experimental signature in both signal scenarios is similar to that of a top quark pair produced in association with large missing transverse momentum. No significant excess over the Standard Model background prediction is observed, and exclusion limits on gluino and top squark masses are set at 95% confidence level. The results extend the LHC run-1 exclusion limit on the gluino mass up to 1460 GeV in the gluino-mediated scenario in the high gluino and low top squark mass region and add an excluded top squark mass region from 745 to 780 GeV for the direct top squark model with a massless lightest neutralino. The results are also reinterpreted to set exclusion limits in a model of vectorlike top quarks.

 

Title:
Search for pair production of Higgs bosons in the b b xAFb b xAF final state using proton-proton collisions at √{s }=13 TeV with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2850 coauthors
Publication:
Physical Review D, Volume 94, Issue 5, id.052002 (PhRvD Homepage)
Publication Date:
09/2016
Origin:
APS
Abstract Copyright:
2016: CERN
DOI:
10.1103/PhysRevD.94.052002
Bibliographic Code:
2016PhRvD..94e2002A

Abstract

A search for Higgs-boson pair production in the b b ¯b b ¯ final state is carried out with 3.2 fb-1 of proton-proton collision data collected at √{s }=13 TeV with the ATLAS detector. The data are consistent with the estimated background and are used to set upper limits on the production cross section of Higgs-boson pairs times branching ratio to b b ¯b b ¯ for both nonresonant and resonant production. In the case of resonant production of Kaluza-Klein gravitons within the Randall-Sundrum model, upper limits in the 24 to 91 fb range are obtained for masses between 600 and 3000 GeV, at the 95% confidence level. The production cross section times branching ratio for nonresonant Higgs-boson pairs is also constrained to be less than 1.22 pb, at the 95% confidence level.

 

Title:
Spin density wave order, topological order, and Fermi surface reconstruction
Authors:
Sachdev, Subir; Berg, Erez; Chatterjee, Shubhayu; Schattner, Yoni
Publication:
Physical Review B, Volume 94, Issue 11, id.115147 (PhRvB Homepage)
Publication Date:
09/2016
Origin:
APS
Abstract Copyright:
2016: American Physical Society
DOI:
10.1103/PhysRevB.94.115147
Bibliographic Code:
2016PhRvB..94k5147S

Abstract

In the conventional theory of density wave ordering in metals, the onset of spin density wave (SDW) order coincides with the reconstruction of the Fermi surfaces into small "pockets." We present models which display this transition, while also displaying an alternative route between these phases via an intermediate phase with topological order, no broken symmetry, and pocket Fermi surfaces. The models involve coupling emergent gauge fields to a fractionalized SDW order, but retain the canonical electron operator in the underlying Hamiltonian. We establish an intimate connection between the suppression of certain defects in the SDW order and the presence of Fermi surface sizes distinct from the Luttinger value in Fermi liquids. We discuss the relevance of such models to the physics of the hole-doped cuprates near optimal doping.

 

Title:
Electronic quasiparticles in the quantum dimer model: Density matrix renormalization group results
Authors:
Lee, Junhyun; Sachdev, Subir; White, Steven R.
Publication:
Physical Review B, Volume 94, Issue 11, id.115112 (PhRvB Homepage)
Publication Date:
09/2016
Origin:
APS
Abstract Copyright:
2016: American Physical Society
DOI:
10.1103/PhysRevB.94.115112
Bibliographic Code:
2016PhRvB..94k5112L

Abstract

We study a recently proposed quantum dimer model for the pseudogap metal state of the cuprates. The model contains bosonic dimers, representing a spin-singlet valence bond between a pair of electrons, and fermionic dimers, representing a quasiparticle with spin-1/2 and charge +e . By density matrix renormalization group calculations on a long but finite cylinder, we obtain the ground-state density distribution of the fermionic dimers for a number of different total densities. From the Friedel oscillations at open boundaries, we deduce that the Fermi surface consists of small hole pockets near (π /2 ,π /2 ) , and this feature persists up to a doping density of 1/16. We also compute the entanglement entropy and find that it closely matches the sum of the entanglement entropies of a critical boson and a low density of free fermions. Our results support the existence of a fractionalized Fermi liquid in this model.

 

Title:
Superconducting pairing in resonant inelastic x-ray scattering
Authors:
Shi, Yifei; Benjamin, David; Demler, Eugene; Klich, Israel
Publication:
Physical Review B, Volume 94, Issue 9, id.094516 (PhRvB Homepage)
Publication Date:
09/2016
Origin:
APS
Abstract Copyright:
2016: American Physical Society
DOI:
10.1103/PhysRevB.94.094516
Bibliographic Code:
2016PhRvB..94i4516S

Abstract

We develop a method to study the effect of the superconducting transition on the resonant inelastic x-ray scattering (RIXS) signal in superconductors with an order parameter with an arbitrary symmetry within a quasiparticle approach. As an example, we compare the direct RIXS signal below and above the superconducting transition for p -wave-type order parameters. For a p -wave order parameter with a nodal line, we show that, counterintuitively, the effect of the gap is most noticeable for momentum transfers in the nodal direction. This phenomenon may be naturally explained as a type of nesting effect.

 

Title:
Rydberg-atom-mediated nondestructive readout of collective rotational states in polar-molecule arrays
Authors:
Kuznetsova, Elena; Rittenhouse, Seth T.; Sadeghpour, H. R.; Yelin, Susanne F.
Publication:
Physical Review A, Volume 94, Issue 3, id.032325 (PhRvA Homepage)
Publication Date:
09/2016
Origin:
APS
Abstract Copyright:
2016: American Physical Society
DOI:
10.1103/PhysRevA.94.032325
Bibliographic Code:
2016PhRvA..94c2325K

Abstract

We analyze the possibility to exploit charge-dipole interaction between a single polar molecule or a one-dimensional (1D) molecular array and a single Rydberg atom to read out molecular rotational populations. We calculate the energy shift of a single Rb (60 s ) atom interacting with a single KRb or RbYb molecule in their lowest two rotational states. At atom-molecule distances, relevant to trapping of molecules in optical lattices, the Rydberg electron energy shifts conditioned on the rotational states, are of the order of several MHz. Atom excitation to a Rydberg state and detection of atomic fluorescence conditioned on a rotational state preserves the molecule, making our scheme a nondestructive measurement of the rotational state. Similarly, a 1D array of polar molecules can shift the electron energy of a blockaded Rydberg superatom. We consider a scheme to read out the molecular array collective rotational states using the conditioned Rydberg energy shifts, and numerically analyze a system with three and five KRb or RbYb molecules interacting with Rb (60 s ) superatom.

 

Title:
Search for heavy long-lived charged R-hadrons with the ATLAS detector in 3.2 fb-1 of proton-proton collision data at √{ s} = 13 TeV
Authors:
Aaboud, M.; Aad, G.; Abbott, B.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2851 coauthors;
Publication:
Physics Letters B, Volume 760, p. 647-665.
Publication Date:
09/2016
Origin:
ELSEVIER
Abstract Copyright:
(c) 2016 Elsevier Science B.V. All rights reserved.
DOI:
10.1016/j.physletb.2016.07.042
Bibliographic Code:
2016PhLB..760..647A

Abstract

A search for heavy long-lived charged R-hadrons is reported using a data sample corresponding to 3.2 fb-1 of proton-proton collisions at √{ s} = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider at CERN. The search is based on observables related to large ionisation losses and slow propagation velocities, which are signatures of heavy charged particles travelling significantly slower than the speed of light. No significant deviations from the expected background are observed. Upper limits at 95% confidence level are provided on the production cross section of long-lived R-hadrons in the mass range from 600 GeV to 2000 GeV and gluino, bottom and top squark masses are excluded up to 1580 GeV, 805 GeV and 890 GeV, respectively.

 

Title:
Search for TeV-scale gravity signatures in high-mass final states with leptons and jets with the ATLAS detector at √{ s} = 13 TeV
Authors:
Aaboud, M.; Aad, G.; Abbott, B.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2857 coauthors;
Publication:
Physics Letters B, Volume 760, p. 520-537.
Publication Date:
09/2016
Origin:
ELSEVIER
Abstract Copyright:
(c) 2016 Elsevier Science B.V. All rights reserved.
DOI:
10.1016/j.physletb.2016.07.030
Bibliographic Code:
2016PhLB..760..520A

Abstract

A search for physics beyond the Standard Model, in final states with at least one high transverse momentum charged lepton (electron or muon) and two additional high transverse momentum leptons or jets, is performed using 3.2 fb-1 of proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015 at √{ s} = 13 TeV. The upper end of the distribution of the scalar sum of the transverse momenta of leptons and jets is sensitive to the production of high-mass objects. No excess of events beyond Standard Model predictions is observed. Exclusion limits are set for models of microscopic black holes with two to six extra dimensions.

 

Title:
Search for scalar leptoquarks in pp collisions at \sqrt{s} = 13 TeV with the ATLAS experiment
Authors:
The ATLAS Collaboration; Aaboud, M.; Aad, G.; Abbott, B.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2846 coauthors;
Publication:
New Journal of Physics, Volume 18, Issue 9, article id. 093016 (2016).
Publication Date:
09/2016
Origin:
IOP
DOI:
10.1088/1367-2630/18/9/093016
Bibliographic Code:
2016NJPh...18i3016T

Abstract

An inclusive search for a new-physics signature of lepton-jet resonances has been performed by the ATLAS experiment. Scalar leptoquarks, pair-produced in pp collisions at \sqrt{s} = 13 TeV at the large hadron collider, have been considered. An integrated luminosity of 3.2 fb-1, corresponding to the full 2015 dataset was used. First (second) generation leptoquarks were sought in events with two electrons (muons) and two or more jets. The observed event yield in each channel is consistent with Standard Model background expectations. The observed (expected) lower limits on the leptoquark mass at 95% confidence level are 1100 and 1050 GeV (1160 and 1040 GeV) for first and second generation leptoquarks, respectively, assuming a branching ratio into a charged lepton and a quark of 100%. Upper limits on the aforementioned branching ratio are also given as a function of leptoquark mass. Compared with the results of earlier ATLAS searches, the sensitivity is increased for leptoquark masses above 860 GeV, and the observed exclusion limits confirm and extend the published results.

 

Title:
Physics of waves: Warning from the deep
Authors:
Heller, Eric
Affiliation:
AA(Eric Heller is in the Departments of Physics and Chemistry and Chemical Biology at Harvard University, Cambridge, Massachusetts 02138, USA; )
Publication:
Nature Physics, Volume 12, Issue 9, pp. 824-825 (2016).
Publication Date:
09/2016
Origin:
NATURE
Abstract Copyright:
(c) 2016: Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.
DOI:
10.1038/nphys3558
Bibliographic Code:
2016NatPh..12..824H

Abstract

Insights from the emerging field of branched flow are directing us towards a way of anticipating the effects of tsunamis. A framework linking bathymetric fluctuations to wave physics marks a promising step forward.

 

Title:
Quasi-two-dimensional metallic hydrogen inside di-phosphide at high pressure
Authors:
Degtyarenko, N. N.; Mazur, E. A.
Affiliation:
AA(National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Kashirskoe sh. 31, 115409 Moscow, Russia), AB(National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Kashirskoe sh. 31, 115409 Moscow, Russia)
Publication:
Journal of Physics: Conference Series, Volume 747, Issue 1, article id. 012029 (2016).
Publication Date:
09/2016
Origin:
IOP
DOI:
10.1088/1742-6596/747/1/012029
Bibliographic Code:
2016JPhCS.747a2029D

Abstract

The method of mathematical modelling was used for the calculation of the structural, electronic, phononic, and other characteristics of various normal phases of phosphorus hydrides with stoichiometry PHk. It was shown that the di-phosphine may form 2D lattice of the metallic hydrogen in it, stabilized by phosphorus atoms under high hydrostatic pressure. The resulting structure with the elements of H-P-H has a locally stable (or metastable) phonon spectrum. The properties of di-phosphine were compared with the properties of similar structures such as the sulphur hydrides.

 

Title:
Laser slowing of CaF molecules to near the capture velocity of a molecular MOT
Authors:
Hemmerling, Boerge; Chae, Eunmi; Ravi, Aakash; Anderegg, Loic; Drayna, Garrett K.; Hutzler, Nicholas R.; Collopy, Alejandra L.; Ye, Jun; Ketterle, Wolfgang; Doyle, John M.
Publication:
Journal of Physics B: Atomic, Molecular, and Optical Physics, Volume 49, Issue 17, article id. 174001 (2016).
Publication Date:
09/2016
Origin:
IOP
DOI:
10.1088/0953-4075/49/17/174001
Bibliographic Code:
2016JPhB...49q4001H

Abstract

Laser slowing of CaF molecules down to the capture velocity of a magneto-optical trap for molecules is achieved. Starting from a two-stage buffer gas beam source, we apply frequency-broadened ‘white-light’ slowing and observe approximately 6× {10}4 CaF molecules in a single pulse with velocities 10 ± 4 m s-1. CaF is a candidate for collisional studies in the mK regime. This work represents a significant step towards magneto-optical trapping of CaF.

 

Title:
Roadmap on neurophotonics
Authors:
Cho, Yong Ku; Zheng, Guoan; Augustine, George J.; Hochbaum, Daniel; Cohen, Adam; Knöpfel, Thomas; Pisanello, Ferruccio; Pavone, Francesco S.; Vellekoop, Ivo M.; Booth, Martin J.; Hu, Song; Zhu, Jiang; Chen, Zhongping; Hoshi, Yoko
Publication:
Journal of Optics, Volume 18, Issue 9, article id. 093007 (2016).
Publication Date:
09/2016
Origin:
IOP
DOI:
10.1088/2040-8978/18/9/093007
Bibliographic Code:
2016JOpt...18i3007C

Abstract

Mechanistic understanding of how the brain gives rise to complex behavioral and cognitive functions is one of science’s grand challenges. The technical challenges that we face as we attempt to gain a systems-level understanding of the brain are manifold. The brain’s structural complexity requires us to push the limit of imaging resolution and depth, while being able to cover large areas, resulting in enormous data acquisition and processing needs. Furthermore, it is necessary to detect functional activities and ‘map’ them onto the structural features. The functional activity occurs at multiple levels, using electrical and chemical signals. Certain electrical signals are only decipherable with sub-millisecond timescale resolution, while other modes of signals occur in minutes to hours. For these reasons, there is a wide consensus that new tools are necessary to undertake this daunting task. Optical techniques, due to their versatile and scalable nature, have great potentials to answer these challenges. Optical microscopy can now image beyond the diffraction limit, record multiple types of brain activity, and trace structural features across large areas of tissue. Genetically encoded molecular tools opened doors to controlling and detecting neural activity using light in specific cell types within the intact brain. Novel sample preparation methods that reduce light scattering have been developed, allowing whole brain imaging in rodent models. Adaptive optical methods have the potential to resolve images from deep brain regions. In this roadmap article, we showcase a few major advances in this area, survey the current challenges, and identify potential future needs that may be used as a guideline for the next steps to be taken.

 

Title:
Nonthermal production of dark radiation and dark matter
Authors:
Reece, Matthew; Roxlo, Thomas
Affiliation:
AA(Department of Physics, Harvard University), AB(Department of Physics, Harvard University)
Publication:
Journal of High Energy Physics, Volume 2016, Issue 9, article id.96, 30 pp.
Publication Date:
09/2016
Origin:
SPRINGER
Keywords:
Cosmology of Theories beyond the SM, CP violation, Supersymmetric Standard Model
Abstract Copyright:
(c) 2016: The Author(s)
DOI:
10.1007/JHEP09(2016)096
Bibliographic Code:
2016JHEP...09..096R

Abstract

Dark matter may be coupled to dark radiation: light degrees of freedom that mediate forces between dark sector particles. Cosmological constraints favor dark radiation that is colder than Standard Model radiation. In models with fixed couplings between dark matter and the Standard Model, these constraints can be difficult to satisfy if thermal equilibrium is assumed in the early universe. We construct a model of asymmetric reheating of the visible and dark sectors from late decays of a long-lived particle (for instance, a modulus). We show, as a proof of principle, that such a model can populate a sufficiently cold dark sector while also generating baryon and dark matter asymmetries through the out-of-equilibrium decay. We frame much of our discussion in terms of the scenario of dissipative dark matter, as in the Double-Disk Dark Matter scenario. However, our results may also be of interest for other scenarios like the Twin Higgs model that are in danger of overproducing dark radiation due to nonnegligible dark-visible couplings.

 

Title:
Measurement of jet activity in top quark events using the eμ final state with two b-tagged jets in pp collisions at √{s}=8 TeV with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2857 coauthors;
Publication:
Journal of High Energy Physics, Volume 2016, Issue 9, article id.74, 62 pp.
Publication Date:
09/2016
Origin:
SPRINGER
Keywords:
Hadron-Hadron scattering (experiments)
Abstract Copyright:
(c) 2016: The Author(s)
DOI:
10.1007/JHEP09(2016)074
Bibliographic Code:
2016JHEP...09..074A

Abstract

Measurements of the jet activity in toverline{t} events produced in proton-proton collisions at √{s}=8 TeV are presented, using 20.3 fb-1 of data collected by the ATLAS experiment at the Large Hadron Collider. The events were selected in the dilepton eμ decay channel with two identified b-jets. The numbers of additional jets for various jet transverse momentum ( p T) thresholds, and the normalised differential cross-sections as a function of p T for the five highest- p T additional jets, were measured in the jet pseudo-rapidity range | η| < 4 .5. The gap fraction, the fraction of events which do not contain an additional jet in a central rapidity region, was measured for several rapidity intervals as a function of the minimum p T of a single jet or the scalar sum of p T of all additional jets. These fractions were also measured in different intervals of the invariant mass of the eμ boverline{b} system. All measurements were corrected for detector effects, and found to be mostly well-described by predictions from next-to-leading-order and leading-order toverline{t} event generators with appropriate parameter choices. The results can be used to further optimise the parameters used in such generators. [Figure not available: see fulltext.]

 

Title:
The gravity duals of modular Hamiltonians
Authors:
Jafferis, Daniel L.; Suh, S. Josephine
Affiliation:
AA(Center for Fundamental Laws of Nature, Harvard University), AB(Center for Theoretical Physics, Massachusetts Institute of Technology)
Publication:
Journal of High Energy Physics, Volume 2016, Issue 9, article id.68, 30 pp.
Publication Date:
09/2016
Origin:
SPRINGER
Keywords:
AdS-CFT Correspondence, Field Theories in Higher Dimensions
Abstract Copyright:
(c) 2016: The Author(s)
DOI:
10.1007/JHEP09(2016)068
Bibliographic Code:
2016JHEP...09..068J

Abstract

In this work, we investigate modular Hamiltonians defined with respect to arbitrary spatial regions in quantum field theory states which have semi-classical gravity duals. We find prescriptions in the gravity dual for calculating the action of the modular Hamiltonian on its defining state, including its dual metric, and also on small excitations around the state. Curiously, use of the covariant holographic entanglement entropy formula leads us to the conclusion that the modular Hamiltonian, which in the quantum field theory acts only in the causal completion of the region, does not commute with bulk operators whose entire gauge-invariant description is space-like to the causal completion of the region.

 

Title:
Measurement of total and differential W + W - production cross sections in proton-proton collisions at √{s}=8 TeV with the ATLAS detector and limits on anomalous triple-gauge-boson couplings
Authors:
Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2844 coauthors;
Publication:
Journal of High Energy Physics, Volume 2016, Issue 9, article id.29, 81 pp.
Publication Date:
09/2016
Origin:
SPRINGER
Keywords:
Electroweak interaction, Hadron-Hadron scattering (experiments), QCD
Abstract Copyright:
(c) 2016: The Author(s)
DOI:
10.1007/JHEP09(2016)029
Bibliographic Code:
2016JHEP...09..029A

Abstract

The production of W boson pairs in proton-proton collisions at √{s}=8 TeV is studied using data corresponding to 20.3 fb-1 of integrated luminosity collected by the ATLAS detector during 2012 at the CERN Large Hadron Collider. The W bosons are reconstructed using their leptonic decays into electrons or muons and neutrinos. Events with reconstructed jets are not included in the candidate event sample. A total of 6636 WW candidate events are observed. Measurements are performed in fiducial regions closely approximating the detector acceptance. The integrated measurement is corrected for all acceptance effects and for the W branching fractions to leptons in order to obtain the total WW production cross section, which is found to be 71 .1 ± 1 .1(stat) - 5.0 + 5.7 (syst) ± 1.4(lumi) pb. This agrees with the next-to-next-to-leading-order Standard Model prediction of 63. 2 - 1.4 + 1.6 (scale) ± 1.2(PDF) pb. Fiducial differential cross sections are measured as a function of each of six kinematic variables. The distribution of the transverse momentum of the leading lepton is used to set limits on anomalous triple-gauge-boson couplings. [Figure not available: see fulltext.]

 

Title:
Precision direct photon spectra at high energy and comparison to the 8 TeV ATLAS data
Authors:
Schwartz, Matthew D.
Affiliation:
AA(Department of Physics, Harvard University)
Publication:
Journal of High Energy Physics, Volume 2016, Issue 9, article id.5, 17 pp.
Publication Date:
09/2016
Origin:
SPRINGER
Keywords:
Effective field theories, Perturbative QCD, Renormalization Group
Abstract Copyright:
(c) 2016: The Author(s)
DOI:
10.1007/JHEP09(2016)005
Bibliographic Code:
2016JHEP...09..005S

Abstract

The direct photon spectrum is computed to the highest currently available precision and compared to ATLAS data from 8 TeV collisions at the LHC. The prediction includes threshold resummation at next-to-next-to-next-to-leading logarithmic order through the program PeTeR, matched to next-to-leading fixed order with fragmentation effects using JetPhox and includes the resummation of leading-logarithmic electroweak Sudakov effects. Remarkably, improved agreement with data can be seen when each component of the calculation is added successively. This comparison demonstrates the importance of both threshold logs and electroweak Sudakov effects. Numerical values for the predictions are included.

 

Title:
Search for resonances in diphoton events at √{s}=13 TeV with the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2855 coauthors;
Publication:
Journal of High Energy Physics, Volume 2016, Issue 9, article id.1, 50 pp.
Publication Date:
09/2016
Origin:
SPRINGER
Keywords:
Beyond Standard Model, Hadron-Hadron scattering (experiments), Hard scattering, Particle and resonance production, proton-proton scattering
Abstract Copyright:
(c) 2016: The Author(s)
DOI:
10.1007/JHEP09(2016)001
Bibliographic Code:
2016JHEP...09..001A

Abstract

Searches for new resonances decaying into two photons in the ATLAS experiment at the CERN Large Hadron Collider are described. The analysis is based on proton-proton collision data corresponding to an integrated luminosity of 3.2 fb-1 at √{s}=13 TeV recorded in 2015. Two searches are performed, one targeted at a spin-2 particle of mass larger than 500 GeV, using Randall-Sundrum graviton states as a benchmark model, and one optimized for a spin-0 particle of mass larger than 200 GeV. Varying both the mass and the decay width, the most significant deviation from the background-only hypothesis is observed at a diphoton invariant mass around 750 GeV with local significances of 3.8 and 3.9 standard deviations in the searches optimized for a spin-2 and spin-0 particle, respectively. The global significances are estimated to be 2.1 standard deviations for both analyses. The consistency between the data collected at 13 TeV and 8 TeV is also evaluated. Limits on the production cross section times branching ratio to two photons for the two resonance types are reported. [Figure not available: see fulltext.]

 

Title:
Search for supersymmetry in a final state containing two photons and missing transverse momentum in \varvec{√{s}} = 13 TeV \varvec{pp} collisions at the LHC using the ATLAS detector
Authors:
Aaboud, M.; Aad, G.; Abbott, B.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2857 coauthors;
Publication:
The European Physical Journal C, Volume 76, Issue 9, article id.517, 23 pp. (EPJC Homepage)
Publication Date:
09/2016
Origin:
SPRINGER
Abstract Copyright:
(c) 2016: The Author(s)
DOI:
10.1140/epjc/s10052-016-4344-x
Bibliographic Code:
2016EPJC...76..517A

Abstract

A search has been made for supersymmetry in a final state containing two photons and missing transverse momentum using the ATLAS detector at the Large Hadron Collider. The search makes use of 3.2{ fb^{-1}} of proton-proton collision data collected at a centre-of-mass energy of 13 TeV in 2015. Using a combination of data-driven and Monte-Carlo-based approaches, the Standard Model background is estimated to be 0.27^{+0.22}_{-0.10} events. No events are observed in the signal region; considering the expected background and its uncertainty, this observation implies a model-independent 95 % CL upper limit of 0.93 fb (3.0 events) on the visible cross section due to physics beyond the Standard Model. In the context of a generalized model of gauge-mediated supersymmetry breaking with a bino-like next-to-lightest supersymmetric particle, this leads to a lower limit of 1650 GeV on the mass of a degenerate octet of gluino states, independent of the mass of the lighter bino-like neutralino.

 

Title:
Study of the rare decays of B^0_s and B^0 into muon pairs from data collected during the LHC Run 1 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 9, article id.513, 31 pp. (EPJC Homepage)
Publication Date:
09/2016
Origin:
SPRINGER
Abstract Copyright:
(c) 2016: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-016-4338-8
Bibliographic Code:
2016EPJC...76..513A

Abstract

A study of the decays B^0_s → μ ^+μ ^- and B^0 → μ ^+μ ^- has been performed using data corresponding to an integrated luminosity of 25 fb^{-1} of 7 and 8 TeV proton-proton collisions collected with the ATLAS detector during the LHC Run 1. For the B^0 dimuon decay, an upper limit on the branching fraction is set at B(B^0 → μ ^+μ ^-) < 4.2 × 10^{-10} at 95 % confidence level. For B^0_s, the branching fraction B(B^0_s → μ ^+μ ^-) = ( 0.9^{+1.1}_{-0.8} ) × 10^{-9} is measured. The results are consistent with the Standard Model expectation with a p value of 4.8 %, corresponding to 2.0 standard deviations.

 

Title:
Charged-particle distributions at low transverse momentum in √{s} = 13 TeV pp interactions measured with the ATLAS detector at the LHC
Authors:
Aaboud, M.; Aad, G.; Abbott, B.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2858 coauthors;
Publication:
The European Physical Journal C, Volume 76, Issue 9, article id.502, 22 pp. (EPJC Homepage)
Publication Date:
09/2016
Origin:
SPRINGER
Abstract Copyright:
(c) 2016: CERN for the benefit of the ATLAS collaboration
DOI:
10.1140/epjc/s10052-016-4335-y
Bibliographic Code:
2016EPJC...76..502A

Abstract

Measurements of distributions of charged particles produced in proton-proton collisions with a centre-of-mass energy of 13 TeV are presented. The data were recorded by the ATLAS detector at the LHC and correspond to an integrated luminosity of 151 μ{b}^{-1}. The particles are required to have a transverse momentum greater than 100 MeV and an absolute pseudorapidity less than 2.5. The charged-particle multiplicity, its dependence on transverse momentum and pseudorapidity and the dependence of the mean transverse momentum on multiplicity are measured in events containing at least two charged particles satisfying the above kinematic criteria. The results are corrected for detector effects and compared to the predictions from several Monte Carlo event generators.

 

Title:
The Screw-Like Movement of a Gliding Bacterium Is Powered by Spiral Motion of Cell-Surface Adhesins
Authors:
Shrivastava, Abhishek; Roland, Thibault; Berg, Howard C.
Publication:
Biophysical Journal, vol. 111, issue 5, pp. 1008-1013
Publication Date:
09/2016
Origin:
CROSSREF
DOI:
10.1016/j.bpj.2016.07.043
Bibliographic Code:
2016BpJ...111.1008S

Abstract

Not Available

 

Title:
Atomic Lattice Disorder in Charge Density Wave Phases of Exfoliated Dichalcogenides (1T-TaS2)
Authors:
Hovden, Robert; Tsen, Adam W.; Liu, Pengzi; Savitzky, Benjamin H.; El Baggari, Ismail; Liu, Yu; Lu, Wenjian; Sun, Yuping; Kim, Philip; Pasupathy, Abhay N.; Kourkoutis, Lena F.
Publication:
eprint arXiv:1609.09486
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Materials Science
Comment:
4 figures in Proceedings of the National Academy of Sciences of the United States of America, 2016; doi:10.1073/pnas.1606044113
Bibliographic Code:
2016arXiv160909486H

Abstract

Charge density waves (CDW) and their concomitant periodic lattice distortions (PLD) govern the electronic properties in many layered transition-metal dichalcogenides. In particular, 1T-TaS2 undergoes a metal-to-insulator phase transition as the PLD becomes commensurate with the crystal lattice. Here we directly image PLDs of the nearly-commensurate (NC) and commensurate (C) phases in thin exfoliated 1T-TaS2 using atomic resolution scanning transmission electron microscopy at room and cryogenic temperature. At low temperatures, we observe commensurate PLD superstructures, suggesting ordering of the CDWs both in- and out-of-plane. In addition, we discover stacking transitions in the atomic lattice that occur via one bond length shifts. Interestingly, the NC PLDs exist inside both the stacking domains and their boundaries. Transitions in stacking order are expected to create fractional shifts in the CDW between layers and may be another route to manipulate electronic phases in layered dichalcogenides.

 

Title:
Topological Superconductivity in a Planar Josephson Junction
Authors:
Pientka, Falko; Keselman, Anna; Berg, Erez; Yacoby, Amir; Stern, Ady; Halperin, Bertrand I.
Publication:
eprint arXiv:1609.09482
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity
Bibliographic Code:
2016arXiv160909482P

Abstract

We consider a two-dimensional electron gas with strong spin-orbit coupling contacted by two superconducting leads, forming a Josephson junction. We show that in the presence of an in-plane Zeeman field the quasi-one-dimensional region between the two superconductors can support a topological superconducting phase hosting Majorana bound states at its ends. We study the phase diagram of the system as a function of the Zeeman field and the phase difference between the two superconductors (treated as an externally controlled parameter). Remarkably, at a phase difference of $\pi$, the topological phase is obtained for almost any value of the Zeeman field and chemical potential. In a setup where the phase is not controlled externally, we find that the system undergoes a first-order topological phase transition when the Zeeman field is varied. At the transition, the phase difference in the ground state changes abruptly from a value close to zero, at which the system is trivial, to a value close to $\pi$, at which the system is topological. The critical current through the junction exhibits a sharp minimum at the critical Zeeman field, and is therefore a natural diagnostic of the transition. We point out that in presence of a symmetry under a modified mirror reflection followed by time reversal, the system belongs to a higher symmetry class and the phase diagram as a function of the phase difference and the Zeeman field becomes richer.

 

Title:
Probing shock geometry via the charge to mass ratio dependence of heavy ion spectra from multiple spacecraft observations of the 2013 November 4 event
Authors:
Zhao, Lulu; Li, Gang; Mason, G. M.; Cohen, C.; Mewaldt, R. A.; Desai, M. I.; Ebert, R. W.; Dayeh, M. A.
Publication:
eprint arXiv:1609.09479
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
Astrophysics - Solar and Stellar Astrophysics
Comment:
9 pages, 4 figures
Bibliographic Code:
2016arXiv160909479Z

Abstract

In large SEP events, ions can be accelerated at CME-driven shocks to very high energies. Spectra of heavy ions in many large SEP events show features such as roll-overs or spectral breaks. In some events when the spectra are plotted in energy/nucleon they can be shifted relative to each other to make the spectral breaks align. The amount of shift is charge-to-mass ratio (Q/A) dependent and varies from event to event. This can be understood if the spectra of heavy ions are organized by the diffusion coefficients (Cohen et al., 2005). In the work of Li et al. (2009), the Q/A dependences of the scaling is related to shock geometry when the CME-driven shock is close to the Sun. For events where multiple in-situ spacecraft observations exist, one may expect that different spacecraft are connected to different portions of the CME-driven shock that have different shock geometries, therefore yielding different Q/A dependence. In this work, we examine one SEP event which occurred on 2013 November 4. We study the Q/A dependence of the energy scaling for heavy ion spectra using Helium, oxygen, and iron ions. Observations from STEREO-A, STEREO-B and ACE are examined. We find that the scalings are different for different spacecraft. We suggest that this is because ACE, STEREO-A and STEREO- B are connected to different parts of the shock that have different shock geometries. Our analysis indicates that studying the Q/A scaling of in-situ particle spectra can serve as a powerful tool to remotely examine the shock geometry for large SEP events.

 

Title:
Observation of a Discrete Time Crystal
Authors:
Zhang, J.; Hess, P. W.; Kyprianidis, A.; Becker, P.; Lee, A.; Smith, J.; Pagano, G.; Potirniche, I.-D.; Potter, A. C.; Vishwanath, A.; Yao, N. Y.; Monroe, C.
Publication:
eprint arXiv:1609.08684
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
Quantum Physics, Condensed Matter - Disordered Systems and Neural Networks, Condensed Matter - Quantum Gases, Condensed Matter - Statistical Mechanics, Physics - Atomic Physics
Comment:
9 pages, 8 figures
Bibliographic Code:
2016arXiv160908684Z

Abstract

Spontaneous symmetry breaking is a fundamental concept in many areas of physics, ranging from cosmology and particle physics to condensed matter. A prime example is the breaking of spatial translation symmetry, which underlies the formation of crystals and the phase transition from liquid to solid. Analogous to crystals in space, the breaking of translation symmetry in time and the emergence of a "time crystal" was recently proposed, but later shown to be forbidden in thermal equilibrium. However, non-equilibrium Floquet systems subject to a periodic drive can exhibit persistent time-correlations at an emergent sub-harmonic frequency. This new phase of matter has been dubbed a "discrete time crystal" (DTC). Here, we present the first experimental observation of a discrete time crystal, in an interacting spin chain of trapped atomic ions. We apply a periodic Hamiltonian to the system under many-body localization (MBL) conditions, and observe a sub-harmonic temporal response that is robust to external perturbations. Such a time crystal opens the door for studying systems with long-range spatial-temporal correlations and novel phases of matter that emerge under intrinsically non-equilibrium conditions.

 

Title:
Realizing topological surface states in a lower-dimensional flat band
Authors:
Potter, Andrew C.; Wang, Chong; Metlitski, Max A.; Vishwanath, Ashvin
Publication:
eprint arXiv:1609.08618
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Mesoscale and Nanoscale Physics
Comment:
22 pages, 2 Figures, 3 Tables
Bibliographic Code:
2016arXiv160908618P

Abstract

The anomalous surface states of symmetry protected topological (SPT) phases are usually thought to be only possible in conjunction with the higher dimensional topological bulk. However, it has recently been realized that a class of anomalous SPT surface states can be realized in the same dimension if symmetries are allowed to act in a nonlocal fashion. An example is the particle-hole symmetric half filled Landau level, which effectively realizes the anomalous surface state of a 3D chiral Topological Insulator (class AIII). A dual description in terms of Dirac composite fermions has also been discussed. Here we explore generalizations of these constructions to multicomponent quantum Hall states. Our results include a duality mapping of the bilayer case to composite bosons with Kramers degeneracy and the possibility of a particle hole symmetric integer quantum Hall state when the number of components is a multiple of eight. Next, we make a further extension by half filling other classes of topological bands and imposing particle hole symmetry. When applied to time-reversal invariant topological insulators we realize a different chiral class (CII) topological surface state. Notably, half-filling a 3D TI band allows for the realization of the surface of the otherwise inaccessible 4D topological insulator, which supports an anomalous 3D Dirac cone. Surface topological orders equivalent to the 3D Dirac cone (from the global anomaly standpoint) are constructed and connections to Witten's SU(2) anomaly are made. These observations may also be useful for numerical simulations of topological surface states and of Dirac fermions without fermion doubling.

 

Title:
Critical thermalization of a disordered dipolar spin system in diamond
Authors:
Kucsko, Georg; Choi, Soonwon; Choi, Joonhee; Maurer, Peter C.; Sumiya, Hitoshi; Onoda, Shinobu; Isoya, Junich; Jelezko, Fedor; Demler, Eugene; Yao, Norman Y.; Lukin, Mikhail D.
Publication:
eprint arXiv:1609.08216
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Disordered Systems and Neural Networks, Quantum Physics
Comment:
16+25 pages, 4+9 figures
Bibliographic Code:
2016arXiv160908216K

Abstract

Statistical mechanics underlies our understanding of macroscopic quantum systems. It is based on the assumption that out-of-equilibrium systems rapidly approach their equilibrium states, forgetting any information about their microscopic initial conditions. This fundamental paradigm is challenged by disordered systems, in which a slowdown or even absence of thermalization is expected. We report the observation of critical thermalization in a three dimensional ensemble of $\sim10^6$ electronic spins coupled via dipolar interactions. By controlling the spin states of nitrogen vacancy color centers in diamond, we observe slow, sub-exponential relaxation dynamics consistent with power laws that exhibit disorder-dependent exponents; this behavior is modified at late times owing to many-body interactions. These observations are quantitatively explained by a resonance counting theory that incorporates the effects of both disorder and interactions.

 

Title:
Inducing Superconducting Correlation in Quantum Hall Edge States
Authors:
Lee, Gil-Ho; Huang, Ko-Fan; Efetov, Dmitri K.; Wei, Di S.; Hart, Sean; Taniguchi, Takashi; Watanabe, Kenji; Yacoby, Amir; Kim, Philip
Publication:
eprint arXiv:1609.08104
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity
Comment:
10 pages, 8 figures
Bibliographic Code:
2016arXiv160908104L

Abstract

The quantum Hall (QH) effect supports a set of chiral edge states at the boundary of a 2-dimensional electron gas (2DEG) system. A superconductor (SC) contacting these states induces correlation of the quasi-particles in the dissipationless 1D chiral QH edge states. If the superconducting electrode is narrower than the superconducting coherence length, the incoming electron are correlated to outgoing hole along the chiral edge state by the Andreev process. In order to realize this crossed Andreev conversion (CAC), it is necessary to fabricate highly transparent and nanometer-scale superconducting junctions to QH system. Here we report the observation of CAC in a graphene QH system contacted with a nanostructured NbN superconducting electrode. The chemical potential of the edge states across the superconducting electrode exhibits a sign reversal, providing direct evidence of CAC. This hybrid SC/QH system is a novel route to create isolated non-Abelian anyonic zero modes, in resonance with the chiral QH edge.

 

Title:
The Complex Circumstellar and Circumbinary Environment of V356 Sgr
Authors:
Lomax, Jamie R.; Fullard, Andrew G.; Malatesta, Michael A.; Babler, Brian; Bednarski, Daniel; Berdis, Jodi R.; Bjorkman, Karen S.; Bjorkman, Jon E.; Carciofi, Alex C.; Davidson, James W., Jr.; Keil, Marcus; Meade, Marilyn R.; Nordsieck, Kenneth; Scheffler, Matt; Hoffman, Jennifer L.; Wisniewski, John P.
Publication:
eprint arXiv:1609.07489
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
Astrophysics - Solar and Stellar Astrophysics
Comment:
14 pages, 6 figures, 5 tables, accepted to MNRAS, Tables 1 and 3 will be available in full at CDS after publication
Bibliographic Code:
2016arXiv160907489L

Abstract

We analyze 45 spectropolarimetric observations of the eclipsing, interacting binary star V356 Sgr, obtained over a period of 21 years, to characterize the geometry of the system's circumstellar material. After removing interstellar polarization from these data, we find the system exhibits a large intrinsic polarization signature arising from electron scattering. In addition, the lack of repeatable eclipses in the polarization phase curves indicates the presence of a substantial pool of scatterers not occulted by either star. We suggest that these scatterers form either a circumbinary disk coplanar with the gainer's accretion disk or an elongated structure perpendicular to the orbital plane of V356 Sgr, possibly formed by bipolar outflows. We also observe small-scale, cycle-to-cycle variations in the magnitude of intrinsic polarization at individual phases, which we interpret as evidence of variability in the amount of scattering material present within and around the system. This may indicate a mass transfer or mass loss rate that varies on the time-scale of the system's orbital period. Finally, we compare the basic polarimetric properties of V356 Sgr with those of the well studied beta Lyr system; the significant differences observed between the two systems suggests diversity in the basic circumstellar geometry of Roche-lobe overflow systems.

 

Title:
On topological approach to local theory of surfaces in Calabi-Yau threefolds
Authors:
Gukov, Sergei; Liu, Chiu-Chu Melissa; Sheshmani, Artan; Yau, Shing-Tung
Publication:
eprint arXiv:1609.04363
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
Mathematics - Algebraic Geometry, High Energy Physics - Theory
Comment:
38 pages
Bibliographic Code:
2016arXiv160904363G

Abstract

We study the web of dualities relating various enumerative invariants, notably Gromov-Witten invariants and invariants that arise in topological gauge theory. In particular, we study Donaldson-Thomas gauge theory and its reductions to D=4 and D=2 which are relevant to the local theory of surfaces in Calabi-Yau threefolds.

 

Title:
Quantum heat waves in a one-dimensional condensate
Authors:
Agarwal, Kartiek; Dalla Torre, Emanuele G.; Schmiedmayer, Jörg; Demler, Eugene
Publication:
eprint arXiv:1609.04046
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Quantum Gases
Comment:
12+epsilon pages + Refs., 8 figures
Bibliographic Code:
2016arXiv160904046A

Abstract

We study the dynamics of phase relaxation between a pair of one-dimensional condensates created by a bi-directional, supersonic `unzipping' of a finite single condensate. We find that the system fractures into different \emph{extensive} chunks of space-time, within which correlations appear thermal but correspond to different effective temperatures. Coherences between different eigen-modes are crucial for understanding the development of such thermal correlations; at no point in time can our system be described by a generalized Gibbs' ensemble despite nearly always appearing locally thermal. We rationalize a picture of propagating fronts of hot and cold sound waves, populated at effective, relativistically red- and blue-shifted temperatures to intuitively explain our findings. The disparity between these hot and cold temperatures vanishes for the case of instantaneous splitting but diverges in the limit where the splitting velocity approaches the speed of sound; in this limit, a sonic boom occurs wherein the system is excited only along an infinitely narrow, and infinitely hot beam. We expect our findings to apply generally to the study of superluminal perturbations in systems with emergent Lorentz symmetry.

 

Title:
Holography of the Dirac Fluid in Graphene with two currents
Authors:
Seo, Yunseok; Song, Geunho; Kim, Philip; Sachdev, Subir; Sin, Sang-Jin
Publication:
eprint arXiv:1609.03582
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
High Energy Physics - Theory, Condensed Matter - Strongly Correlated Electrons
Comment:
5 pages, 1 figure
Bibliographic Code:
2016arXiv160903582S

Abstract

Recent experiments have uncovered evidence of the strongly coupled nature of the graphene: the Wiedemann-Franz law is violated by up to a factor of 20 near the charge neutral point. We describe this strongly-coupled plasma by a holographic model in which there are two distinct conserved U(1) currents. We find that our analytic results for the transport coefficients for two current model have a significantly improved match to the density dependence of the experimental data than the models with only one current. We also discuss the origin of the two currents.

 

Title:
Physics at a Higgs Factory
Authors:
Reece, Matthew
Publication:
eprint arXiv:1609.03018
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
High Energy Physics - Phenomenology
Comment:
proceedings of Hong Kong IAS conference; includes some new plots of future collider EWPT
Bibliographic Code:
2016arXiv160903018R

Abstract

I give an overview of the physics potential at possible future $e^+ e^-$ colliders, including the ILC, FCC-ee, and CEPC. The goal is to explain some of the measurements that can be done in the context of electroweak precision tests and Higgs couplings, to compare some of the options under consideration, and to put the measurements in context by summarizing their implications for some new physics scenarios. This is a writeup of a plenary talk at the Hong Kong University of Science and Technology Jockey Club Institute for Advanced Study Program on High Energy Physics Conference, January 18--21, 2016. Some previously unpublished electroweak precision results for FCC-ee and CEPC are included.

 

Title:
Sisyphus Laser Cooling of a Polyatomic Molecule
Authors:
Kozyryev, Ivan; Baum, Louis; Matsuda, Kyle; Augenbraun, Benjamin L.; Anderegg, Loic; Sedlack, Alexander P.; Doyle, John M.
Publication:
eprint arXiv:1609.02254
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
Physics - Atomic Physics
Bibliographic Code:
2016arXiv160902254K

Abstract

We perform magnetically-assisted Sisyphus laser cooling of the triatomic free radical strontium monohydroxide (SrOH). This is achieved with principal optical cycling in the rotationally closed $P\left(N"=1\right)$ branch of either the $\tilde{X}^{2}\Sigma^{+}\left(000\right)\leftrightarrow\tilde{A}^{2}\Pi_{1/2}\left(000\right)$ or the $\tilde{X}^{2}\Sigma^{+}\left(000\right)\leftrightarrow\tilde{B}^{2}\Sigma^{+}\left(000\right)$ vibronic transitions. Molecules lost into the excited vibrational states during the cooling process are repumped back through the $\tilde{B}\left(000\right)$ state for both the $\left(100\right)$ level of the Sr-O stretching mode and the $\left(02^{0}0\right)$ level of the bending mode. The transverse temperature of a SrOH molecular beam is reduced in one dimension by two orders of magnitude to $\sim700\ {\rm \mu K}$. This approach opens a path towards creating a variety of ultracold polyatomic molecules, including much larger ones, by means of direct laser cooling.

 

Title:
Quantum fluctuation induced time of flight correlations of an interacting trapped Bose gas
Authors:
Lovas, Izabella; Dóra, Balázs; Demler, Eugene; Zaránd, Gergely
Publication:
eprint arXiv:1609.01751
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
Condensed Matter - Quantum Gases
Comment:
11 pages, 7 figures
Bibliographic Code:
2016arXiv160901751L

Abstract

We investigate numerically the momentum correlations in a two dimensional, harmonically trapped interacting Bose system at $T=0$ temperature, by using a particle number preserving Bogoliubov approximation. Due to particle number conservation, interaction induced quantum fluctuations of the quasi-condensate lead to a large anti-correlation dip between particles of wave numbers $\mathbf{k}$ and $-\mathbf{k}$ for $|\mathbf{k}|\sim 1/R_c$, with $R_c$ typical size of the condensate. The anti-correlation dip found is a clear fingerprint of coherent quantum fluctuations of the condensate. In contrast, for larger wave numbers, $|\mathbf{k}| >> 1/R_c$, a weak positive correlation is found between particles of wave numbers $\mathbf{k}$ and $-\mathbf{k}$, in accordance with the Bogoliubov result for homogeneous interacting systems.

 

Title:
Brane Brick Models in the Mirror
Authors:
Franco, Sebastian; Lee, Sangmin; Seong, Rak-Kyeong; Vafa, Cumrun
Publication:
eprint arXiv:1609.01723
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
High Energy Physics - Theory, Mathematical Physics, Mathematics - Algebraic Geometry
Comment:
74 pages, 56 figures
Bibliographic Code:
2016arXiv160901723F

Abstract

Brane brick models are Type IIA brane configurations that encode the $2d$ $\mathcal{N}=(0,2)$ gauge theories on the worldvolume of D1-branes probing toric Calabi-Yau 4-folds. We use mirror symmetry to improve our understanding of this correspondence and to provide a systematic approach for constructing brane brick models starting from geometry. The mirror configuration consists of D5-branes wrapping 4-spheres and the gauge theory is determined by how they intersect. We also explain how $2d$ $(0,2)$ triality is realized in terms of geometric transitions in the mirror geometry. Mirror symmetry leads to a geometric unification of dualities in different dimensions, where the order of duality is $n-1$ for a Calabi-Yau $n$-fold. This makes us conjecture the existence of a quadrality symmetry in $0d$. Finally, we comment on how the M-theory lift of brane brick models connects to the classification of $2d$ $(0,2)$ theories in terms of 4-manifolds.

 

Title:
A remark on our paper "Negative Holomorphic curvature and positive canonical bundle"
Authors:
Wu, Damin; Yau, Shing-Tung
Publication:
eprint arXiv:1609.01377
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
Mathematics - Differential Geometry
Bibliographic Code:
2016arXiv160901377W

Abstract

This is a continuation of our first paper in [WY16]. There are two purposes of this paper: One is to give a proof of the main result in [WY16] without going through the argument depending on numerical effectiveness. The other one is to provide a proof of our conjecture, mentioned in [TY], where the assumption of negative holomorphic sectional curvature is dropped to quasi-negative. We should note that a solution to our conjecture is also provided by Diverio-Trapani [DT]. Both proofs depend on our argument in [WY16]. But our argument here makes use of the argument given by the second author and Cheng in [CY75].

 

Title:
Punctures for Theories of Class $\mathcal{S}_\Gamma$
Authors:
Heckman, Jonathan J.; Jefferson, Patrick; Rudelius, Tom; Vafa, Cumrun
Publication:
eprint arXiv:1609.01281
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
High Energy Physics - Theory, Mathematics - Commutative Algebra, Mathematics - Combinatorics
Comment:
39 pages
Bibliographic Code:
2016arXiv160901281H

Abstract

With the aim of understanding compactifications of 6D superconformal field theories to four dimensions, we study punctures for theories of class $\mathcal{S}_{\Gamma}$. The class $\mathcal{S}_{\Gamma}$ theories arise from M5-branes probing $\mathbb{C}^2 / \Gamma$, an ADE singularity. The resulting 4D theories descend from compactification on Riemann surfaces decorated with punctures. We show that for class $\mathcal{S}_{\Gamma}$ theories, a puncture is specified by singular boundary conditions for fields in the 5D quiver gauge theory obtained from compactification of the 6D theory on a cylinder geometry. We determine general boundary conditions and study in detail solutions with first order poles. This yields a generalization of the Nahm pole data present for $1/2$ BPS punctures for theories of class $\mathcal{S}$. Focusing on specific algebraic structures, we show how the standard discussion of nilpotent orbits and its connection to representations of $\mathfrak{su}(2)$ generalizes in this broader context.

 

Title:
A 2D Stress Tensor for 4D Gravity
Authors:
Kapec, Daniel; Mitra, Prahar; Raclariu, Ana-Maria; Strominger, Andrew
Publication:
eprint arXiv:1609.00282
Publication Date:
09/2016
Origin:
ARXIV
Keywords:
High Energy Physics - Theory, General Relativity and Quantum Cosmology
Comment:
12 pages. v2: updated acknowledgements
Bibliographic Code:
2016arXiv160900282K

Abstract

We use the subleading soft-graviton theorem to construct an operator $T_{zz}$ whose insertion in the four-dimensional tree-level quantum gravity $\mathcal{S}$-matrix obeys the Virasoro-Ward identities of the energy momentum tensor of a two-dimensional conformal field theory (CFT$_2$). The celestial sphere at Minkowskian null infinity plays the role of the Euclidean sphere of the CFT$_2$, with the Lorentz group acting as the unbroken $SL(2,\mathbb{C})$ subgroup.


 go to the Top
 go to Most Recent Faculty Publications