Faculty Publications: November, 2015
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Title:  Absence of DisorderDriven MetalInsulator Transitions in Simple Holographic Models  
Authors:  Grozdanov, Sašo; Lucas, Andrew; Sachdev, Subir; Schalm, Koenraad  
Publication:  Physical Review Letters, Volume 115, Issue 22, id.221601 (PhRvL Homepage)  
Publication Date:  11/2015  
Origin:  APS  
PACS Keywords:  Gauge/string duality, Disordered solids  
Abstract Copyright:  2015: American Physical Society  
DOI:  10.1103/PhysRevLett.115.221601  
Bibliographic Code:  2015PhRvL.115v1601G 
Abstract
We study electrical transport in a strongly coupled strange metal in two spatial dimensions at finite temperature and charge density, holographically dual to the EinsteinMaxwell theory in an asymptotically fourdimensional antide Sitter space spacetime, with arbitrary spatial inhomogeneity, up to mild assumptions including emergent isotropy. In condensed matter, these are candidate models for exotic strange metals without longlived quasiparticles. We prove that the electrical conductivity is bounded from below by a universal minimal conductance: the quantum critical conductivity of a clean, chargeneutral plasma. Beyond nonperturbatively justifying meanfield approximations to disorder, our work demonstrates the practicality of new hydrodynamic insight into holographic transport.
Title:  Prethermal Floquet Steady States and Instabilities in the Periodically Driven, Weakly Interacting BoseHubbard Model  
Authors:  Bukov, Marin; Gopalakrishnan, Sarang; Knap, Michael; Demler, Eugene  
Publication:  Physical Review Letters, Volume 115, Issue 20, id.205301 (PhRvL Homepage)  
Publication Date:  11/2015  
Origin:  APS  
PACS Keywords:  BoseEinstein condensates in optical potentials, Nonlinear dynamics and chaos, Quantum transport, Nonequilibrium and irreversible thermodynamics  
Abstract Copyright:  2015: American Physical Society  
DOI:  10.1103/PhysRevLett.115.205301  
Bibliographic Code:  2015PhRvL.115t5301B 
Abstract
We explore prethermal Floquet steady states and instabilities of the weakly interacting twodimensional BoseHubbard model subject to periodic driving. We develop a description of the nonequilibrium dynamics, at arbitrary drive strength and frequency, using a weakcoupling conserving approximation. We establish the regimes in which conventional (zeromomentum) and unconventional [(π ,π )momentum] condensates are stable on intermediate time scales. We find that condensate stability is enhanced by increasing the drive strength, because this decreases the bandwidth of quasiparticle excitations and thus impedes resonant absorption and heating. Our results are directly relevant to a number of current experiments with ultracold bosons.
Title:  Commentary: The social science of creativity and research practice: Physical scientists, take notice  
Authors:  Odumosu, Toluwalogo; Tsao, Jeffrey Y.; Narayanamurti, Venkatesh  
Publication:  Physics Today, vol. 68, issue 11, pp. 89  
Publication Date:  11/2015  
Origin:  CROSSREF  
DOI:  10.1063/PT.3.2959  
Bibliographic Code:  2015PhT....68k...8O 
Abstract
Not Available
Title:  Study of the energy dependence of the underlying event in protonantiproton collisions  
Authors:  Aaltonen, T.; Albrow, M.; Amerio, S.;... Franklin, M.;... and 400 coauthors  
Publication:  Physical Review D, Volume 92, Issue 9, id.092009 (PhRvD Homepage)  
Publication Date:  11/2015  
Origin:  APS  
PACS Keywords:  Production, Electrons, Muons  
Abstract Copyright:  2015: American Physical Society  
DOI:  10.1103/PhysRevD.92.092009  
Bibliographic Code:  2015PhRvD..92i2009A 
Abstract
We study charged particle production (pT>0.5 GeV /c , η <0.8 ) in protonantiproton collisions at total centerofmass energies √{s }=300 GeV , 900 GeV, and 1.96 TeV. We use the direction of the charged particle with the largest transverse momentum in each event to define three regions of η ϕ space: "toward", "away", and "transverse." The average number and the average scalar pT sum of charged particles in the transverse region are sensitive to the modeling of the "underlying event." The transverse region is divided into a MAX and MIN transverse region, which helps separate the "hard component" (initial and finalstate radiation) from the "beambeam remnant" and multiple parton interaction components of the scattering. The centerofmass energy dependence of the various components of the event is studied in detail. The data presented here can be used to constrain and improve QCD Monte Carlo models, resulting in more precise predictions at the LHC energies of 13 and 14 TeV.
Title:  Searches for Higgs boson pair production in the h h →b b τ τ , γ γ W W* , γ γ b b , b b b b channels with the ATLAS detector  
Authors:  Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... ; and 2864 coauthors 

Publication:  Physical Review D, Volume 92, Issue 9, id.092004 (PhRvD Homepage)  
Publication Date:  11/2015  
Origin:  APS  
PACS Keywords:  Extensions of electroweak Higgs sector, Standardmodel Higgs bosons  
Abstract Copyright:  2015: CERN  
DOI:  10.1103/PhysRevD.92.092004  
Bibliographic Code:  2015PhRvD..92i2004A 
Abstract
Searches for both resonant and nonresonant Higgs boson pair production are performed in the h h →b b τ τ , γ γ W W* final states using 20.3 fb1 of p p collision data at a centerofmass energy of 8 TeV recorded with the ATLAS detector at the Large Hadron Collider. No evidence of their production is observed and 95% confidencelevel upper limits on the production cross sections are set. These results are then combined with the published results of the h h →γ γ b b , b b b b analyses. An upper limit of 0.69 (0.47) pb on the nonresonant h h production is observed (expected), corresponding to 70 (48) times the SM g g →h h cross section. For production via narrow resonances, crosssection limits of h h production from a heavy Higgs boson decay are set as a function of the heavy Higgs boson mass. The observed (expected) limits range from 2.1 (1.1) pb at 260 GeV to 0.011 (0.018) pb at 1000 GeV. These results are interpreted in the context of two simplified scenarios of the Minimal Supersymmetric Standard Model.
Title:  Search for new light gauge bosons in Higgs boson decays to fourlepton final states in p p collisions at √{s }=8 TeV with the ATLAS detector at the LHC  
Authors:  Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... ; and 2821 coauthors 

Publication:  Physical Review D, Volume 92, Issue 9, id.092001 (PhRvD Homepage)  
Publication Date:  11/2015  
Origin:  APS  
PACS Keywords:  Applications of electroweak models to specific processes, Extensions of electroweak Higgs sector, Supersymmetric models, Production  
Abstract Copyright:  2015: CERN  
DOI:  10.1103/PhysRevD.92.092001  
Bibliographic Code:  2015PhRvD..92i2001A 
Abstract
This paper presents a search for Higgs bosons decaying to four leptons, either electrons or muons, via one or two light exotic gauge bosons Z_{d}, H →Z Z_{d}→4 ℓ or H →Z_{d}Z_{d} →4 ℓ. The search was performed using p p collision data corresponding to an integrated luminosity of about 20 fb^{1} at the centerofmass energy of √{s }=8 TeV recorded with the ATLAS detector at the Large Hadron Collider. The observed data are well described by the Standard Model prediction. Upper bounds on the branching ratio of H →Z Z_{d}→4 ℓ and on the kinetic mixing parameter between the Z_{d} and the Standard Model hypercharge gauge boson are set in the range (1  9 )×1 0^{5} and (4  17 )×1 0^{2} respectively, at 95% confidence level assuming the Standard Model branching ratio of H →Z Z^{*}→4 ℓ, for Z_{d} masses between 15 and 55 GeV. Upper bounds on the effective mass mixing parameter between the Z and the Z_{d} are also set using the branching ratio limits in the H →Z Z_{d}→4 ℓ search, and are in the range (1.5  8.7)×1 0^{4} for 15 <m_{Zd}<35 GeV. Upper bounds on the branching ratio of H →Z_{d}Z_{d}→4 ℓ and on the Higgs portal coupling parameter, controlling the strength of the coupling of the Higgs boson to dark vector bosons are set in the range (2  3 )×10^{5} and (1  10 )×10^{4} respectively, at 95% confidence level assuming the Standard Model Higgs boson production cross sections, for Z_{d} masses between 15 and 60 GeV.
Title:  Ab initio tightbinding Hamiltonian for transition metal dichalcogenides  
Authors:  Fang, Shiang; Kuate Defo, Rodrick; Shirodkar, Sharmila N.; Lieu, Simon; Tritsaris, Georgios A.; Kaxiras, Efthimios  
Publication:  Physical Review B, Volume 92, Issue 20, id.205108 (PhRvB Homepage)  
Publication Date:  11/2015  
Origin:  APS  
PACS Keywords:  Methods of electronic structure calculations, Electronic structure of nanoscale materials: clusters nanoparticles nanotubes and nanocrystals, Multilayers superlattices heterostructures, Other inorganic semiconductors  
Abstract Copyright:  2015: American Physical Society  
DOI:  10.1103/PhysRevB.92.205108  
Bibliographic Code:  2015PhRvB..92t5108F 
Abstract
We present an accurate ab initio tightbinding Hamiltonian for the transition metal dichalcogenides, MoS2, MoSe2, WS2, WSe2, with a minimal basis (the d orbitals for the metal atoms and p orbitals for the chalcogen atoms) based on a transformation of the KohnSham density functional theory Hamiltonian to a basis of maximally localized Wannier functions. The truncated tightbinding Hamiltonian, with only onsite, first, and partial second neighbor interactions, including spinorbit coupling, provides a simple physical picture and the symmetry of the main bandstructure features. Interlayer interactions between adjacent layers are modeled by transferable hopping terms between the chalcogen p orbitals. The fullrange tightbinding Hamiltonian can be reduced to hybridorbital k .p effective Hamiltonians near the band extrema that capture important lowenergy excitations. These ab initio Hamiltonians can serve as the starting point for applications to interacting manybody physics including optical transitions and Berry curvature of bands, of which we give some examples.
Title:  1 /f α noise and generalized diffusion in random Heisenberg spin systems  
Authors:  Agarwal, Kartiek; Demler, Eugene; Martin, Ivar  
Publication:  Physical Review B, Volume 92, Issue 18, id.184203 (PhRvB Homepage)  
Publication Date:  11/2015  
Origin:  APS  
PACS Keywords:  Renormalization group methods, Quantized spin models, Disordered structures, amorphous and glassy solids, Superconducting quantum interference devices  
Abstract Copyright:  2015: American Physical Society  
DOI:  10.1103/PhysRevB.92.184203  
Bibliographic Code:  2015PhRvB..92r4203A 
Abstract
We study the "fluxnoise" spectrum of randombond quantum Heisenberg spin systems using a realspace renormalization group (RSRG) procedure that accounts for both the renormalization of the system Hamiltonian and of a generic probe that measures the noise. For spin chains, we find that the dynamical structure factor Sq(f ) , at finite wave vector q , exhibits a powerlaw behavior both at high and low frequencies f , with exponents that are connected to one another and to an anomalous dynamical exponent through relations that differ at T =0 and T =∞ . The lowfrequency powerlaw behavior of the structure factor is inherited by any generic probe with a finite bandwidth and is of the form 1 /fα with 0.5 <α <1 . An analytical calculation of the structure factor, assuming a limiting distribution of the RG flow parameters (spin size, length, bond strength) confirms numerical findings. More generally, we demonstrate that this form of the structure factor, at high temperatures, is a manifestation of anomalous diffusion which directly follows from a generalized spindiffusion propagator. We also argue that 1 /f noise is intimately connected to manybodylocalization at finite temperatures. In two dimensions, the RG procedure is less reliable; however, it becomes convergent for quasionedimensional geometries where we find that onedimensional 1 /fα behavior is recovered at low frequencies; the latter configurations are likely representative of paramagnetic spin networks that produce 1 /fα noise in SQUIDs.
Title:  Fluctuating orders and quenched randomness in the cuprates  
Authors:  Nie, Laimei; Sierens, Lauren E. Hayward; Melko, Roger G.; Sachdev, Subir; Kivelson, Steven A.  
Publication:  Physical Review B, Volume 92, Issue 17, id.174505 (PhRvB Homepage)  
Publication Date:  11/2015  
Origin:  APS  
PACS Keywords:  Cuprate superconductors, Chargedensitywave systems  
Abstract Copyright:  2015: American Physical Society  
DOI:  10.1103/PhysRevB.92.174505  
Bibliographic Code:  2015PhRvB..92q4505N 
Abstract
We study a quasitwodimensional classical LandauGinzburgWilson effective field theory in the presence of quenched disorder in which incommensurate chargedensity wave and superconducting orders are intertwined. The disorder precludes longrange chargedensity wave order, but not superconducting or nematic order. We select three representative sets of input parameters and compute the corresponding chargedensity wave structure factors using both largeN techniques and classical Monte Carlo simulations. Where nematicity and superconductivity coexist at low temperature, the peak height of the chargedensity wave structure factor decreases monotonically as a function of increasing temperature, unlike what is seen in xray experiments on YBa2Cu3O6 +x . Conversely, where the thermal evolution of the chargedensity wave structure factor qualitatively agrees with experiments, the nematic correlation length, computed to oneloop order, is shorter than the chargedensity wave correlation length.
Title:  Measurement of colour flow with the jet pull angle in t t bar events using the ATLAS detector at √{ s} = 8 TeV  
Authors:  Aad, G.; Abbott, B.; Abdallah, J.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2845 coauthors  
Publication:  Physics Letters B, Volume 750, p. 475493.  
Publication Date:  11/2015  
Origin:  ELSEVIER  
Abstract Copyright:  (c) 2015 CERN for the benefit of the ATLAS Collaboration  
DOI:  10.1016/j.physletb.2015.09.051  
Bibliographic Code:  2015PhLB..750..475A 
Abstract
The distribution and orientation of energy inside jets is predicted to be an experimental handle on colour connections between the hardscatter quarks and gluons initiating the jets. This Letter presents a measurement of the distribution of one such variable, the jet pull angle. The pull angle is measured for jets produced in t t bar events with one W boson decaying leptonically and the other decaying to jets using 20.3 fb1 of data recorded with the ATLAS detector at a centreofmass energy of √{ s} = 8 TeV at the LHC. The jet pull angle distribution is corrected for detector resolution and acceptance effects and is compared to various models.
Title:  Measurement of transverse energyenergy correlations in multijet events in pp collisions at √{ s} = 7 TeV using the ATLAS detector and determination of the strong coupling constant αs (mZ)  
Authors:  Aad, G.; Abbott, B.; Abdallah, J.;;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2851 coauthors  
Publication:  Physics Letters B, Volume 750, p. 427447.  
Publication Date:  11/2015  
Origin:  ELSEVIER  
Abstract Copyright:  (c) 2015 CERN for the benefit of the ATLAS Collaboration  
DOI:  10.1016/j.physletb.2015.09.050  
Bibliographic Code:  2015PhLB..750..427A 
Abstract
High transverse momentum jets produced in pp collisions at a centre of mass energy of 7 TeV are used to measure the transverse energyenergy correlation function and its associated azimuthal asymmetry. The data were recorded with the ATLAS detector at the LHC in the year 2011 and correspond to an integrated luminosity of 158 pb^{1}. The selection criteria demand the average transverse momentum of the two leading jets in an event to be larger than 250 GeV. The data at detector level are well described by Monte Carlo event generators. They are unfolded to the particle level and compared with theoretical calculations at nexttoleadingorder accuracy. The agreement between data and theory is good and provides a precision test of perturbative Quantum Chromodynamics at large momentum transfers. From this comparison, the strong coupling constant given at the Z boson mass is determined to be α_{s} (m_{Z}) = 0.1173 ± 0.0010 (exp.) _{0.0026}^{+0.0065} (theo.).
Title:  Onchip zeroindex metamaterials  
Authors:  Li, Yang; Kita, Shota; Muñoz, Philip; Reshef, Orad; Vulis, Daryl I.; Yin, Mei; Lončar, Marko; Mazur, Eric  
Publication:  Nature Photonics, Volume 9, Issue 11, pp. 738742 (2015).  
Publication Date:  11/2015  
Origin:  NATURE  
Abstract Copyright:  (c) 2015: Nature Publishing Group  
DOI:  10.1038/nphoton.2015.198  
Bibliographic Code:  2015NaPho...9..738L 
Abstract
Metamaterials with a refractive index of zero exhibit physical properties such as infinite phase velocity and wavelength. However, there is no way to implement these materials on a photonic chip, restricting the investigation and application of zeroindex phenomena to simple shapes and small scales. We designed and fabricated an onchip integrated metamaterial with a refractive index of zero in the optical regime. Light refracts perpendicular to the facets of a prism made of this metamaterial, directly demonstrating that the index of refraction is zero. The metamaterial consists of lowaspectratio silicon pillar arrays embedded in a polymer matrix and clad by gold films. This structure can be fabricated using standard planar processes over a large area in arbitrary shapes and can efficiently couple to photonic integrated circuits and other optical elements. This novel onchip metamaterial platform opens the door to exploring the physics of zero index and its applications in integrated optics.
Title:  The 2015 superresolution microscopy roadmap  
Authors:  Hell, Stefan W.; Sahl, Steffen J.; Bates, Mark; Zhuang, Xiaowei; Heintzmann, Rainer; Booth, Martin J.; Bewersdorf, Joerg; Shtengel, Gleb; Hess, Harald; Tinnefeld, Philip; Honigmann, Alf; Jakobs, Stefan; Testa, Ilaria; Cognet, Laurent; Lounis, Brahim; Ewers, Helge; Davis, Simon J.; Eggeling, Christian; Klenerman, David; Willig, Katrin I.; Vicidomini, Giuseppe; Castello, Marco; Diaspro, Alberto; Cordes, Thorben  
Publication:  Journal of Physics D: Applied Physics, Volume 48, Issue 44, article id. 443001 (2015).  
Publication Date:  11/2015  
Origin:  IOP  
DOI:  10.1088/00223727/48/44/443001  
Bibliographic Code:  2015JPhD...48R3001H 
Abstract
Farfield optical microscopy using focused light is an important tool in a number of scientific disciplines including chemical, (bio)physical and biomedical research, particularly with respect to the study of living cells and organisms. Unfortunately, the applicability of the optical microscope is limited, since the diffraction of light imposes limitations on the spatial resolution of the image. Consequently the details of, for example, cellular protein distributions, can be visualized only to a certain extent. Fortunately, recent years have witnessed the development of ‘superresolution’ farfield optical microscopy (nanoscopy) techniques such as stimulated emission depletion (STED), ground state depletion (GSD), reversible saturated optical (fluorescence) transitions (RESOLFT), photoactivation localization microscopy (PALM), stochastic optical reconstruction microscopy (STORM), structured illumination microscopy (SIM) or saturated structured illumination microscopy (SSIM), all in one way or another addressing the problem of the limited spatial resolution of farfield optical microscopy. While SIM achieves a twofold improvement in spatial resolution compared to conventional optical microscopy, STED, RESOLFT, PALM/STORM, or SSIM have all gone beyond, pushing the limits of optical image resolution to the nanometer scale. Consequently, all superresolution techniques open new avenues of biomedical research. Because the field is so young, the potential capabilities of different superresolution microscopy approaches have yet to be fully explored, and uncertainties remain when considering the best choice of methodology. Thus, even for experts, the road to the future is sometimes shrouded in mist. The superresolution optical microscopy roadmap of Journal of Physics D: Applied Physics addresses this need for clarity. It provides guidance to the outstanding questions through a collection of short review articles from experts in the field, giving a thorough discussion on the concepts underlying superresolution optical microscopy, the potential of different approaches, the importance of label optimization (such as reversible photoswitchable proteins) and applications in which these methods will have a significant impact.
Title:  Polycrystalline anatase titanium dioxide microring resonators with negative thermooptic coefficient  
Authors:  Reshef, Orad; Shtyrkova, Katia; Moebius, Michael G.; GriesseNascimento, Sarah; Spector, Steven; Evans, Christopher C.; Ippen, Erich; Mazur, Eric  
Publication:  Journal of the Optical Society of America B, vol. 32, issue 11, p. 2288  
Publication Date:  11/2015  
Origin:  CROSSREF  
DOI:  10.1364/JOSAB.32.002288  
Bibliographic Code:  2015JOSAB..32.2288R 
Abstract
Not Available
Title:  On the ground state wave function of matrix theory  
Authors:  Lin, YingHsuan; Yin, Xi  
Publication:  Journal of High Energy Physics, Volume 2015, article id. #27, 19 pp.  
Publication Date:  11/2015  
Origin:  SPRINGER  
Keywords:  Supersymmetric gauge theory, Field Theories in Lower Dimensions, M(atrix) Theories, MTheory  
Abstract Copyright:  (c) 2015: The Author(s)  
DOI:  10.1007/JHEP11(2015)027  
Bibliographic Code:  2015JHEP...11..027L 
Abstract
We propose an explicit construction of the leading terms in the asymptotic expansion of the ground state wave function of BFSS SU( N ) matrix quantum mechanics. Our proposal is consistent with the expected factorization property in various limits of the Coulomb branch, and involves a different scaling behavior from previous suggestions. We comment on some possible physical implications.
Title:  VLBI for Gravity Probe B: the guide star, IM Pegasi  
Authors:  Bartel, N.; Bietenholz, M. F.; Lebach, D. E.; Ransom, R. R.; Ratner, M. I.; Shapiro, I. I.  
Publication:  Classical and Quantum Gravity, Volume 32, Issue 22, article id. 224021 (2015). (CQGra Homepage)  
Publication Date:  11/2015  
Origin:  IOP  
DOI:  10.1088/02649381/32/22/224021  
Bibliographic Code:  2015CQGra..32v4021B 
Abstract
We review the radio very long baseline interferometry (VLBI) observations of the guide star, IM Peg, and three compact extragalactic reference sources, made in support of the NASA/Stanford gyroscope relativity mission, Gravity Probe B (GPB). The main goal of the observations was the determination of the proper motion of IM Peg relative to the distant Universe. VLBI observations made between 1997 and 2005 yield a proper motion of IM Peg of 20.83 ± 0.09 mas yr‑1 in α and 27.27 ± 0.09 mas yr‑1 in δ in a celestial reference frame of extragalactic radio galaxies and quasars virtually identical to the International Celestial Reference Frame 2 (ICRF2). They also yield a parallax for IM Peg of 10.37 ± 0.07 mas, corresponding to a distance of 96.4 ± 0.7 pc. The uncertainties are standard errors with statistical and estimated systematic contributions added in quadrature. These results met the prelaunch requirements of the GPB mission to not discernibly degrade the estimates of the geodetic and framedragging effects.
Title:  The Gravity Probe B test of general relativity  
Authors:  Everitt, C. W. F.; Muhlfelder, B.; DeBra, D. B.;... Shapiro, I. I.;... .; and 91 coauthors  
Publication:  Classical and Quantum Gravity, Volume 32, Issue 22, article id. 224001 (2015). (CQGra Homepage)  
Publication Date:  11/2015  
Origin:  IOP  
DOI:  10.1088/02649381/32/22/224001  
Bibliographic Code:  2015CQGra..32v4001E 
Abstract
The Gravity Probe B mission provided two new quantitative tests of Einstein’s theory of gravity, general relativity (GR), by cryogenic gyroscopes in Earth’s orbit. Data from four gyroscopes gave a geodetic driftrate of 6601.8 ± 18.3 marcs yr^{1} and a framedragging of 37.2 ± 7.2 marcs yr^{1}, to be compared with GR predictions of 6606.1 and 39.2 marcs yr^{1} (1 marcs = 4.848 × 10^{9} radians). The present paper introduces the science, engineering, data analysis, and heritage of Gravity Probe B, detailed in the accompanying 20 CQG papers.
Title:  NonKähler SYZ Mirror Symmetry  
Authors:  Lau, SiuCheong; Tseng, LiSheng; Yau, ShingTung  
Publication:  Communications in Mathematical Physics, Volume 340, Issue 1, pp.145170  
Publication Date:  11/2015  
Origin:  SPRINGER  
Abstract Copyright:  (c) 2015: SpringerVerlag Berlin Heidelberg  
DOI:  10.1007/s0022001524541  
Bibliographic Code:  2015CMaPh.340..145L 
Abstract
We study SYZ mirror symmetry in the context of nonKähler CalabiYau manifolds. In particular, we study the sixdimensional Type II supersymmetric SU(3) systems with RamondRamond fluxes, and generalize them to higher dimensions. We show that FourierMukai transform provides the mirror map between these Type IIA and Type IIB supersymmetric systems in the semiflat setting. This is concretely exhibited by nilmanifolds.
Title:  Dynamical Cooper pairing in nonequilibrium electronphonon systems  
Authors:  Knap, Michael; Babadi, Mehrtash; Refael, Gil; Martin, Ivar; Demler, Eugene  
Publication:  eprint arXiv:1511.07874  
Publication Date:  11/2015  
Origin:  ARXIV  
Keywords:  Condensed Matter  Superconductivity, Condensed Matter  Strongly Correlated Electrons, Quantum Physics  
Bibliographic Code:  2015arXiv151107874K 
Abstract
Ultrafast laser pulses have been used to manipulate complex quantum materials and to induce dynamical phase transitions. One of the most striking examples is the transient enhancement of superconductivity in several classes of materials upon irradiating them with high intensity pulses of terahertz light. Motivated by these experiments we analyze the Cooper pairing instabilities in nonequilibrium electronphonon systems. We demonstrate that the light induced nonequilibrium state of phonons results in the following phenomena: an increase in the time averaged superconducting coupling constant, its periodic modulation, and an increase in the electron scattering. While the first two enhance Cooper pairing, the third one suppresses it. We analyze the competition between these effects and show that in a broad range of parameters the dynamic enhancement of pair formation dominates over the increase in the scattering rate. This opens the possibility of transient light induced superconductivity at temperatures that are considerably higher than the equilibrium transition temperatures. Our results pave new pathways for engineering hightemperature lightinduced superconducting states.
Title:  InfiniteDimensional Fermionic Symmetry in Supersymmetric Gauge Theories  
Authors:  Dumitrescu, Thomas T.; He, Temple; Mitra, Prahar; Strominger, Andrew  
Publication:  eprint arXiv:1511.07429  
Publication Date:  11/2015  
Origin:  ARXIV  
Keywords:  High Energy Physics  Theory, High Energy Physics  Phenomenology  
Comment:  39 pages  
Bibliographic Code:  2015arXiv151107429D 
Abstract
We establish the existence of an infinitedimensional fermionic symmetry in fourdimensional supersymmetric gauge theories by analyzing semiclassical photino dynamics in abelian ${\cal N}=1$ theories with charged matter. The symmetry is parametrized by a spinorvalued function on an asymptotic $S^2$ at null infinity. It is not manifest at the level of the Lagrangian, but acts nontrivially on physical states, and its Ward identity is the soft photino theorem. The infinitedimensional fermionic symmetry resides in the same ${\cal N}=1$ supermultiplet as the physically nontrivial large gauge symmetries associated with the soft photon theorem.
Title:  Nonthermal production of dark radiation and dark matter  
Authors:  Reece, Matthew; Roxlo, Thomas  
Publication:  eprint arXiv:1511.06768  
Publication Date:  11/2015  
Origin:  ARXIV  
Keywords:  High Energy Physics  Phenomenology  
Bibliographic Code:  2015arXiv151106768R 
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 longlived particle (for instance, a modulus). We show, as a proofofprinciple, 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 DoubleDisk 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 darkvisible couplings.
Title:  Griffiths effects and slow dynamics in nearly manybody localized systems  
Authors:  Gopalakrishnan, Sarang; Agarwal, Kartiek; Huse, David A.; Demler, Eugene; Knap, Michael  
Publication:  eprint arXiv:1511.06389  
Publication Date:  11/2015  
Origin:  ARXIV  
Keywords:  Condensed Matter  Disordered Systems and Neural Networks, Condensed Matter  Statistical Mechanics  
Comment:  11 pages, 2 figures  
Bibliographic Code:  2015arXiv151106389G 
Abstract
The lowfrequency response of systems near a manybody localization transition can be dominated by rare regions that are locally critical or ``in the other phase''. It is known that, in one dimension, these rare regions can cause the d.c. conductivity and diffusion constant to vanish even inside the delocalized thermal phase. Here, we present a general analysis of such Griffiths effects in the thermal phase near the manybody localization transition: we consider both onedimensional and higherdimensional systems, subject to quenched randomness, and discuss both linear response (including the frequency and wavevectordependent conductivity) and more general dynamics. In all the regimes we consider, we identify observables that are dominated by rareregion effects. In some cases (onedimensional systems and Floquet systems with no extensive conserved quantities), essentially all longtime local observables are dominated by rareregion effects; in others, generic observables are instead dominated by hydrodynamic longtime tails throughout the thermal phase, and one must look at specific probes, such as spin echo, to see Griffiths behavior.
Title:  Siteresolved imaging of a fermionic Mott insulator  
Authors:  Greif, Daniel; Parsons, Maxwell F.; Mazurenko, Anton; Chiu, Christie S.; Blatt, Sebastian; Huber, Florian; Ji, Geoffrey; Greiner, Markus  
Publication:  eprint arXiv:1511.06366  
Publication Date:  11/2015  
Origin:  ARXIV  
Keywords:  Condensed Matter  Quantum Gases  
Comment:  6+7 pages  
Bibliographic Code:  2015arXiv151106366G 
Abstract
The complexity of quantum manybody systems originates from the interplay of strong interactions, quantum statistics, and the large number of quantummechanical degrees of freedom. Probing these systems on a microscopic level with singlesite resolution offers unique insight with unprecedented control. Here we report siteresolved imaging of twocomponent fermionic Mott insulators, metals, and band insulators using ultracold atoms in a square lattice. We observe large, defectfree 2D Mott insulators for strong repulsive interactions. For intermediate interactions we observe a coexistence of phases. From comparison to theory we find trapaveraged entropies per particle of $1.0\,k_{\mathrm{B}}$ and local entropies as low as $0.5\,k_{\mathrm{B}}$. This experiment is a vital step towards probing quantummechanical models in regimes inaccessible by modern theoretical methods.
Title:  On the construction of charged operators inside an eternal black hole  
Authors:  Guica, Monica; Jafferis, Daniel L.  
Publication:  eprint arXiv:1511.05627  
Publication Date:  11/2015  
Origin:  ARXIV  
Keywords:  High Energy Physics  Theory  
Comment:  44 pp  
Bibliographic Code:  2015arXiv151105627G 
Abstract
We revisit the holographic construction of (approximately) local bulk operators inside an eternal AdS black hole in terms of operators in the boundary CFTs. If the bulk operator carries charge, the construction must involve a qualitatively new object: a Wilson line that stretches between the two boundaries of the eternal black hole. This operator  more precisely, its zero mode  cannot be expressed in terms of the boundary currents and only exists in entangled states dual to twosided geometries, which suggests that it is a statedependent operator. We determine the action of the Wilson line on the relevant subspaces of the total Hilbert space, and show that it behaves as a local operator from the point of view of either CFT. For the case of three bulk dimensions, we give explicit expressions for the charged bulk field and the Wilson line. Furthermore, we show that when acting on the thermofield double state, the Wilson line may be extracted from a limit of certain standard CFT operator expressions. We also comment on the relationship between the Wilson line and previously discussed mirror operators in the eternal black hole.
Title:  Ftheory and the Classification of Little Strings  
Authors:  Bhardwaj, Lakshya; Del Zotto, Michele; Heckman, Jonathan J.; Morrison, David R.; Rudelius, Tom; Vafa, Cumrun  
Publication:  eprint arXiv:1511.05565  
Publication Date:  11/2015  
Origin:  ARXIV  
Keywords:  High Energy Physics  Theory  
Comment:  76 pages, 7 figures  
Bibliographic Code:  2015arXiv151105565B 
Abstract
Little string theories (LSTs) are UV complete nonlocal 6D theories decoupled from gravity in which there is an intrinsic string scale. In this paper we present a systematic approach to the construction of supersymmetric LSTs via the geometric phases of Ftheory. Our central result is that all LSTs with more than one tensor multiplet are obtained by a mild extension of 6D superconformal field theories (SCFTs) in which the theory is supplemented by an additional, nondynamical tensor multiplet, analogous to adding an affine node to an ADE quiver, resulting in a negative semidefinite Dirac pairing. We also show that all 6D SCFTs naturally embed in an LST. Motivated by physical considerations, we show that in geometries where we can verify the presence of two elliptic fibrations, exchanging the roles of these fibrations amounts to Tduality in the 6D theory compactified on a circle.
Title:  Strong quantum scarring by local impurities  
Authors:  Luukko, Perttu J. J.; Drury, Byron; Klales, Anna; Kaplan, Lev; Heller, Eric J.; Räsänen, Esa  
Publication:  eprint arXiv:1511.04198  
Publication Date:  11/2015  
Origin:  ARXIV  
Keywords:  Quantum Physics  
Comment:  Letterlength draft with Supplementary Material  
Bibliographic Code:  2015arXiv151104198L 
Abstract
We discover and characterize strong quantum scars, or eigenstates resembling classical periodic orbits, in twodimensional quantum wells perturbed by local impurities. These scars are not explained by ordinary scar theory, which would require the existence of short, moderately unstable periodic orbits in the perturbed system. Instead, they are supported by classical resonances in the unperturbed system and the resulting quantum neardegeneracy. Even in the case of a large number of randomly scattered impurities, the scars prefer distinct orientations that extremize the overlap with the impurities. We demonstrate that these preferred orientations can be used for highly efficient transport of quantum wave packets across the perturbed potential landscape. Assisted by the scars, wavepacket recurrences are significantly stronger than in the unperturbed system. Together with the controllability of the preferred orientations, this property may be very useful for quantum transport applications.
Title:  N=4 Superconformal Bootstrap of the K3 CFT  
Authors:  Lin, YingHsuan; Shao, ShuHeng; SimmonsDuffin, David; Wang, Yifan; Yin, Xi  
Publication:  eprint arXiv:1511.04065  
Publication Date:  11/2015  
Origin:  ARXIV  
Keywords:  High Energy Physics  Theory  
Comment:  60 pages, 9 figures  
Bibliographic Code:  2015arXiv151104065L 
Abstract
We study twodimensional (4,4) superconformal field theories of central charge c=6, corresponding to nonlinear sigma models on K3 surfaces, using the superconformal bootstrap. This is made possible through a surprising relation between the BPS N=4 superconformal blocks with c=6 and bosonic Virasoro conformal blocks with c=28, and an exact result on the moduli dependence of a certain integrated BPS 4point function. Nontrivial bounds on the nonBPS spectrum in the K3 CFT are obtained as functions of the CFT moduli, that interpolate between the free orbifold points and singular CFT points. We observe directly from the CFT perspective the signature of a continuous spectrum above a gap at the singular moduli, and find numerically an upper bound on this gap that is saturated by the $A_1$ N=4 cigar CFT. We also derive an analytic upper bound on the first nonzero eigenvalue of the scalar Laplacian on K3 in the large volume regime, that depends on the K3 moduli data. As two byproducts, we find an exact equivalence between a class of BPS N=2 superconformal blocks and Virasoro conformal blocks in two dimensions, and an upper bound on the fourpoint functions of operators of sufficiently low scaling dimension in three and four dimensional CFTs.
Title:  Fractional Quantum Hall Effect and MTheory  
Authors:  Vafa, Cumrun  
Publication:  eprint arXiv:1511.03372  
Publication Date:  11/2015  
Origin:  ARXIV  
Keywords:  Condensed Matter  Mesoscale and Nanoscale Physics, High Energy Physics  Theory  
Comment:  28 pages. Major clarifications and extensions, including the distinction between edge modes for the superconducting and sharp edge boundary conditions. Section 4.2 expanded and contains a selfcontained summary of the proposal. Possibility of lifting the construction to 3+1 d and potential experimental realization of nonabelian YangMills theory for topological insulators is pointed out  
Bibliographic Code:  2015arXiv151103372V 
Abstract
We propose a unifying model for FQHE which on the one hand connects it to recent developments in string theory and on the other hand leads to new predictions for the principal series of experimentally observed FQH systems with filling fraction $\nu ={n\over 2n\pm1}$ as well as those with $\nu ={m\over m+2}$. Our model relates these series to minimal unitary models of the Virasoro and superVirasoro algebra and is based on $SL(2, {\bf C})$ ChernSimons theory in Euclidean space or $SL(2,{\bf R})\times SL(2,{\bf R})$ ChernSimons theory in Minkowski space. This theory, which has also been proposed as a soluble model for 2+1 dimensional quantum gravity, and its N=1 supersymmetric cousin, provide effective descriptions of FQHE. The principal series corresponds to quantized levels for the two $SL(2,{\bf R})$'s such that the diagonal $SL(2,{\bf R})$ has level $ 1$. The model predicts, contrary to standard lore, that for principal series of FQH systems the quasiholes possess nonabelian statistics. For the multilayer case we propose that complex ADE ChernSimons theories provide effective descriptions, where the rank of the ADE is mapped to the number of layers. Six dimensional $(2,0)$ ADE theories on the Riemann surface $\Sigma$ provides a realization of FQH systems in Mtheory. Moreover we propose that the qdeformed version of ChernSimons theories are related to the anisotropic limit of FQH systems which splits the zeroes of the Laughlin wave function. Extensions of the model to 3+1 dimensions, which realize topological insulators with nonabelian topologically twisted YangMills theory is pointed out.
Title:  Superconformal Index, BPS Monodromy and Chiral Algebras  
Authors:  Cecotti, Sergio; Song, Jaewon; Vafa, Cumrun; Yan, Wenbin  
Publication:  eprint arXiv:1511.01516  
Publication Date:  11/2015  
Origin:  ARXIV  
Keywords:  High Energy Physics  Theory  
Comment:  91+2 pages, 4 figures; v2 references added  
Bibliographic Code:  2015arXiv151101516C 
Abstract
We show that specializations of the 4d $\mathcal{N}=2$ superconformal index labeled by an integer $N$ is given by $\textrm{Tr}\,{\cal M}^N$ where ${\cal M}$ is the KontsevichSoibelman monodromy operator for BPS states on the Coulomb branch. We provide evidence that the states enumerated by these limits of the index lead to a family of 2d chiral algebras $\mathcal{A}_{N}$. This generalizes the recent results for the $N=1$ case which corresponds to the Schur limit of the superconformal index. We show that this specialization of the index leads to the same integrand as that of the elliptic genus of compactification of the superconformal theory on $S^2\times T^2$ where we turn on $\frac{1}{2} N$ units of $U(1)_r$ flux on $S^2$.
Title:  CalabiYau modular forms in limit: Elliptic Fibrations  
Authors:  Haghighat, Babak; Movasati, Hossein; Yau, ShingTung  
Publication:  eprint arXiv:1511.01310  
Publication Date:  11/2015  
Origin:  ARXIV  
Keywords:  Mathematics  Algebraic Geometry, High Energy Physics  Theory  
Comment:  24 pages  
Bibliographic Code:  2015arXiv151101310H 
Abstract
We study the limit of CalabiYau modular forms, and in particular, those resulting in classical modular forms. We then study two parameter families of elliptically fibred CalabiYau fourfolds and describe the modular forms arising from the degeneracy loci. In the case of elliptically fibred CalabiYau threefolds our approach gives a mathematical proof of many observations about modularity properties of topological string amplitudes starting with the work of Candelas, Font, Katz and Morrison. In the case of CalabiYau fourfolds we derive new identities not computed before.
Title:  SUSY Higgs Mass and Collider Signals with a Hidden Valley  
Authors:  Nakai, Yuichiro; Reece, Matthew; Sato, Ryosuke  
Publication:  eprint arXiv:1511.00691  
Publication Date:  11/2015  
Origin:  ARXIV  
Keywords:  High Energy Physics  Phenomenology  
Comment:  29 pages, 8 figures  
Bibliographic Code:  2015arXiv151100691N 
Abstract
We propose a framework of supersymmetric extensions of the Standard Model that can ameliorate both the SUSY Higgs mass problem and the missing superpartner problem. New vectorlike matter fields couple to the Higgs and provide new loop contributions to its mass. New Yukawa couplings are sizable and large supersymmetry breaking is not needed to lift the Higgs mass. To avoid a Landau pole for the new Yukawa couplings, these fields are charged under a new gauge group, which confines and leads to a Hidden Valleylike phenomenology. The Hidden Valley sector is almost supersymmetric and ordinary sparticles decay to exotic new states which decay back to Standard Model particles and gravitinos with reduced missing energy. We construct a simplified model to simulate this scenario and find a viable parameter space of specific benchmark models which ameliorates both of the major phenomenological problems with supersymmetry.
Title:  Elliptic Virasoro Conformal Blocks  
Authors:  Iqbal, Amer; Kozcaz, Can; Yau, ShingTung  
Publication:  eprint arXiv:1511.00458  
Publication Date:  11/2015  
Origin:  ARXIV  
Keywords:  High Energy Physics  Theory  
Comment:  35 pages  
Bibliographic Code:  2015arXiv151100458I 
Abstract
We study certain six dimensional theories arising on $(p,q)$ brane webs living on $\mathbb{R}\times S^1$. These brane webs are dual to toric elliptically fibered CalabiYau threefolds. The compactification of the space on which the brane web lives leads to a deformation of the partition functions equivalent to the elliptic deformation of the DingIohara algebra. We compute the elliptic version DotsenkoFateev integrals and show that they reproduce the instanton counting of the six dimensional theory.
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