Faculty Publications: May, 2018
Query Results from the Smithsonian/NASA Astrophysics Data System (ADS)
The following are Harvard Physics faculty members' publications, added to the ADS database last month. Please note that some publications which appeared in print last month may not be included in the database (and therefore may not appear on this list) until the following month.
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Title: | Refined Topological Branes | |
Authors: | Kozçaz, Can; Shakirov, Shamil; Vafa, Cumrun; Yan, Wenbin | |
Publication: | eprint arXiv:1805.00993 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | High Energy Physics - Theory | |
Bibliographic Code: | 2018arXiv180500993K |
Abstract
We study the open refined topological string amplitudes using the refined topological vertex. We determine the refinement of holonomies necessary to describe the boundary conditions of open amplitudes (which in particular satisfy the required integrality properties). We also derive the refined holonomies using the refined Chern-Simons theory.
Title: | The Berry curvature dipole current in transition metal dichalcogenides family | |
Authors: | You, Jhih-Shih; Fang, Shiang; Xu, Su-Yang; Kaxiras, Efthimios; Low, Tony | |
Publication: | eprint arXiv:1805.02157 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science | |
Comment: | 4 figures | |
Bibliographic Code: | 2018arXiv180502157Y |
Abstract
We study the quantum nonlinear Hall effect in two-dimensional materials with time-reversal symmetry. When only one mirror line exists, a transverse charge current occurs in second-order response to an external electric field, as a result of the Berry curvature dipole in momentum space. Candidate 2D materials to observe this effect are two-dimensional transition-metal dichalcogenides~(TMDCs). First we use an ab initio based tight-binding approach to demonstrate that monolayer $T_d$-stricture TMDCs exhibit a finite Berry curvature dipole. In the $1H$ and $1T'$ phase of TMDCs, we show the emergence of finite Berry curvature dipole with the application of strain and displacement field respectively.
Title: | Quantum Nonlinear Optics in Atomically Thin Materials | |
Authors: | Wild, Dominik S.; Shahmoon, Ephraim; Yelin, Susanne F.; Lukin, Mikhail D. | |
Publication: | eprint arXiv:1805.04805 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | Condensed Matter - Mesoscale and Nanoscale Physics, Quantum Physics | |
Bibliographic Code: | 2018arXiv180504805W |
Abstract
We show that a nonlinear optical response associated with a resonant, atomically thin material can be dramatically enhanced by placing it in front of a partially reflecting mirror, rendering otherwise weakly nonlinear systems suitable for experiments and applications involving quantum nonlinear optics. Our approach exploits the nonlinear response of long-lived polariton resonances that arise at particular distances between the material and the mirror. The scheme is entirely based on free-space optics, eliminating the need for cavities or complex nanophotonic structures. We analyze a specific implementation based on exciton-polariton resonances in two-dimensional semiconductors and discuss the role of imperfections and loss.
Title: | Variational study of U(1) and SU(2) lattice gauge theories with Gaussian states in 1+1 dimensions | |
Authors: | Sala, P.; Shi, T.; Kühn, S.; Bañuls, M. C.; Demler, E.; Cirac, J. I. | |
Publication: | eprint arXiv:1805.05190 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | High Energy Physics - Lattice, Condensed Matter - Strongly Correlated Electrons, Quantum Physics | |
Comment: | 19 pages, 6 figures | |
Bibliographic Code: | 2018arXiv180505190S |
Abstract
We introduce a method to investigate the static and dynamic properties of both Abelian and non-Abelian lattice gauge models in 1+1 dimensions. Specifically, we identify a set of transformations that disentangle different degrees of freedom, and apply a simple Gaussian variational ansatz to the resulting Hamiltonian. To demonstrate the suitability of the method, we analyze both static and dynamic aspects of string breaking for the U(1) and SU(2) gauge models. We benchmark our results against tensor network simulations and observe excellent agreement, although the number of variational parameters in the Gaussian ansatz is much smaller.
Title: | A Direct Probe of Mass Density Near Inspiraling Binary Black Holes | |
Authors: | Randall, Lisa; Xianyu, Zhong-Zhi | |
Publication: | eprint arXiv:1805.05335 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | General Relativity and Quantum Cosmology, Astrophysics - High Energy Astrophysical Phenomena, High Energy Physics - Phenomenology, High Energy Physics - Theory | |
Comment: | 6 pages | |
Bibliographic Code: | 2018arXiv180505335R |
Abstract
Now that LIGO has revealed the existence of a large number of binary black holes, identifying their origin becomes an important challenge. They might originate in more isolated regions of the galaxy or alternatively they might reside in dense environments such as galactic centers or globular clusters. In the latter case, their center of mass motion as well as their orbital parameters should lead to observable changes in the waveforms, which would reflect their gravitational interactions with the surrounding matter. This would be reflected in the gravitational wave signal by a net phase change or even a time-dependent Doppler shift. We show that this time-dependence might be observable in future space gravitational wave detectors such as LISA which could provide direct information about the black hole binary environments and otherwise invisible ambient mass.
Title: | Science Impacts of the SPHEREx All-Sky Optical to Near-Infrared Spectral Survey II: Report of a Community Workshop on the Scientific Synergies Between the SPHEREx Survey and Other Astronomy Observatories | |
Authors: | Doré, Olivier; Werner, Michael W.; Ashby, Matthew L. N.;... Dvorkin, Cora;... and 59 coauthors | |
Publication: | eprint arXiv:1805.05489 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | Astrophysics - Instrumentation and Methods for Astrophysics, Astrophysics - Cosmology and Nongalactic Astrophysics, Astrophysics - Earth and Planetary Astrophysics, Astrophysics - Astrophysics of Galaxies, Astrophysics - Solar and Stellar Astrophysics | |
Comment: | 50 pages, 24 figures, more details at http://spherex.caltech.edu | |
Bibliographic Code: | 2018arXiv180505489D |
Abstract
SPHEREx is a proposed NASA MIDEX mission selected for Phase A study. SPHEREx would carry out the first all-sky spectral survey in the near infrared. At the end of its two-year mission, SPHEREx would obtain 0.75-to-5$\mu$m spectra of every 6.2 arcsec pixel on the sky, with spectral resolution R>35 and a 5-$\sigma$ sensitivity AB$>$19 per spectral/spatial resolution element. More details concerning SPHEREx are available at http://spherex.caltech.edu. The SPHEREx team has proposed three specific science investigations to be carried out with this unique data set: cosmic inflation, interstellar and circumstellar ices, and the extra-galactic background light. Though these three themes are undoubtedly compelling, they are far from exhausting the scientific output of SPHEREx. Indeed, SPHEREx would create a unique all-sky spectral database including spectra of very large numbers of astronomical and solar system targets, including both extended and diffuse sources. These spectra would enable a wide variety of investigations, and the SPHEREx team is dedicated to making the data available to the community to enable these investigations, which we refer to as Legacy Science. To that end, we have sponsored two workshops for the general scientific community to identify the most interesting Legacy Science themes and to ensure that the SPHEREx data products are responsive to their needs. In February of 2016, some 50 scientists from all fields met in Pasadena to develop these themes and to understand their implications for the SPHEREx mission. The 2016 workshop highlighted many synergies between SPHEREx and other contemporaneous astronomical missions, facilities, and databases. Consequently, in January 2018 we convened a second workshop at the Center for Astrophysics in Cambridge to focus specifically on these synergies. This white paper reports on the results of the 2018 SPHEREx workshop.
Title: | They Might Be Giants: An Efficient Color-Based Selection of Red Giant Stars | |
Authors: | Conroy, Charlie; Bonaca, Ana; Naidu, Rohan P.; Eisenstein, Daniel J.; Johnson, Benjamin D.; Dotter, Aaron; Finkbeiner, Douglas P. | |
Publication: | eprint arXiv:1805.05954 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | Astrophysics - Astrophysics of Galaxies | |
Comment: | 7 pages, 6 figures, ApJL Accepted | |
Bibliographic Code: | 2018arXiv180505954C |
Abstract
We present a color-based method for identifying red giants based on Pan-STARRS grz and WISE W1 and W2 photometry. We utilize a subsample of bright stars with precise parallaxes from Gaia DR2 to verify that the color-based selection reliably separates dwarfs from giants. The selection is conservative in the sense that contamination is small (~30%) but not all giants are included (the selection primarily identifies K giants). The color-based selection can be applied to stars brighter than $W1\approx16$, more than two magnitudes fainter than techniques relying on shallower 2MASS photometry. Many streams and clouds are visible in the resulting sky maps, especially when binned by Gaia DR2 proper motions, including the Sagittarius stream, the Hercules-Aquila Cloud, the Eastern Banded Structure, Monoceros, and the Virgo Overdensity. In addition to the characterization of new and known stellar streams, we expect that this method for selecting red giants will enable detailed analysis of the diffuse stellar halo to distances exceeding 100 kpc.
Title: | Superconductivity from Valley Fluctuations and Approximate SO(4) Symmetry in a Weak Coupling Theory of Twisted Bilayer Graphene | |
Authors: | You, Yi-Zhuang; Vishwanath, Ashvin | |
Publication: | eprint arXiv:1805.06867 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Superconductivity | |
Comment: | 13 pages, 7 figures, 3 tables | |
Bibliographic Code: | 2018arXiv180506867Y |
Abstract
We develop a weak coupling approach to superconductivity in twisted bilayer graphene, starting from the Fermi liquid regime. A key observation is that near half filling, the fermiology consists of well nested Fermi pockets derived from opposite valleys, leading to enhanced valley fluctuation, which in turn can mediate superconductivity. This scenario is studied within the random phase approximation. We find that inter-valley electron pairing with either chiral ($d+i d$ mixed with $p-i p$) or helical form factor is the dominant instability. An approximate SO(4) spin-valley symmetry implies a near degeneracy of spin-singlet and triplet pairing. On increasing interactions, commensurate inter-valley coherence wave (IVCW) order can arise, with simultaneous condensation at the three "M" points in the Brillouin Zone, and a $2\times2$ pattern in real space. In simple treatments though, this leads to a full gap at fillings $\pm (1/2+1/8)$, slightly away from half-filling. An SO(4) symmetry breaking "anti-Hunds" coupling favors the spin-singlet order both for the IVCW and the superconductor, consistent with observations. Mott insulators derived from phase fluctuating superconductors are also discussed, which exhibit both symmetry protected and intrinsic topological orders.
Title: | Comparison of \nu\mu-Ar multiplicity distributions observed by MicroBooNE to GENIE model predictions | |
Authors: | Adams, C.; An, R.; Anthony, J.;... Guenette, R.;... ; and 161 coauthors | |
Publication: | eprint arXiv:1805.06887 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | High Energy Physics - Experiment, Physics - Instrumentation and Detectors | |
Comment: | 31 pages, 39 figures, 10 tables | |
Bibliographic Code: | 2018arXiv180506887A |
Abstract
We measure a large set of observables in inclusive charged current muon neutrino scattering on argon with the MicroBooNE liquid argon time projection chamber operating at Fermilab. We evaluate three neutrino interaction models based on the widely used GENIE event generator using these observables. The measurement uses a data set consisting of neutrino interactions with a final state muon candidate fully contained within the MicroBooNE detector. These data were collected in 2016 with the Fermilab Booster Neutrino Beam, which has an average neutrino energy of 800 MeV, using an exposure corresponding to 5e19 protons-on-target. The analysis employs fully automatic event selection and charged particle track reconstruction and uses a data-driven technique to separate neutrino interactions from cosmic ray background events. We find that GENIE models consistently describe the shapes of a large number of kinematic distributions for fixed observed multiplicity, but we show an indication that the observed multiplicity fractions deviate from GENIE expectations.
Title: | Relaxation and Domain Formation in Incommensurate 2D Heterostructures | |
Authors: | Carr, Stephen; Massatt, Daniel; Torrisi, Steven B.; Cazeaux, Paul; Luskin, Mitchell; Kaxiras, Efthimios | |
Publication: | eprint arXiv:1805.06972 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | Condensed Matter - Mesoscale and Nanoscale Physics | |
Comment: | 6 pages, 4 figures | |
Bibliographic Code: | 2018arXiv180506972C |
Abstract
We introduce configuration space as a natural representation for calculating the mechanical relaxation patterns of incommensurate two-dimensional (2D) bilayers, bypassing supercell approximations to encompass aperiodic relaxation patterns. The approach can be applied to a wide variety of 2D materials through the use of a continuum model in combination with a generalized stacking fault energy for interlayer interactions. We present computational results for small-angle twisted bilayer graphene and molybdenum disulfide (MoS$_2$), a representative material of the transition metal dichalcogenide (TMDC) family of 2D semiconductors. We calculate accurate relaxations for MoS$_2$ even at small twist-angle values, enabled by the fact that our approach does not rely on empirical atomistic potentials for interlayer coupling. The results demonstrate the efficiency of the configuration space method by computing relaxations with minimal computational cost for twist angles down to $0.05^\circ$, which is smaller than what can be explored by any available real space techniques. We also outline a general explanation of domain formation in 2D bilayers with nearly-aligned lattices, taking advantage of the relationship between real space and configuration space.
Title: | Efficient Topological Materials Discovery Using Symmetry Indicators | |
Authors: | Tang, Feng; Po, Hoi Chun; Vishwanath, Ashvin; Wan, Xiangang | |
Publication: | eprint arXiv:1805.07314 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science | |
Bibliographic Code: | 2018arXiv180507314T |
Abstract
Although the richness of spatial symmetries has led to a rapidly expanding inventory of possible topological crystalline (TC) phases of electrons, physical realizations have been slow to materialize due to the practical difficulty to ascertaining band topology in realistic calculations. Here, we integrate the recently established theory of symmetry indicators of band topology into first-principle band-structure calculations, and test it on a databases of previously synthesized crystals. The combined algorithm is found to efficiently unearth topological materials and predict topological properties like protected surface states. On applying our algorithm to just 8 out of the 230 space groups, we already discover numerous materials candidates displaying a diversity of topological phenomena, which are simultaneously captured in a single sweep. The list includes recently proposed classes of TC insulators that had no previous materials realization as well as other topological phases, including: (i) a screw-protected 3D TC insulator, \b{eta}-MoTe2, with gapped surfaces except for 1D helical "hinge" states; (ii) a rotation-protected TC insulator BiBr with coexisting surface Dirac cones and hinge states; (iii) non-centrosymmetric Z2 topological insulators undetectable using the well-established parity criterion, AgXO (X=Na,K,Rb); (iv) a Dirac semimetal MgBi2O6; (v) a Dirac nodal-line semimetal AgF2; and (vi) a metal with three-fold degenerate band crossing near the Fermi energy, AuLiMgSn. Our work showcases how the recent theoretical insights on the fundamentals of band structures can aid in the practical goal of discovering new topological materials.
Title: | Enhanced Sensitivity to Ultralight Bosonic Dark Matter in the Spectra of the Linear Radical SrOH | |
Authors: | Kozyryev, Ivan; Lasner, Zack; Doyle, John M. | |
Publication: | eprint arXiv:1805.08185 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | Physics - Atomic Physics | |
Bibliographic Code: | 2018arXiv180508185K |
Abstract
Coupling between Standard Model particles and theoretically well-motivated ultralight dark matter (UDM) candidates can lead to time variation of fundamental constants including the proton-to-electron mass ratio $\mu\equiv m_{p}/m_{e}\approx1836$. The presence of nearly-degenerate vibrational energy levels of different character in polyatomic molecules can result in significantly enhanced relative energy shifts in molecular spectra originating from $\partial_{t}\mu$, relaxing experimental complexity required for high-sensitivity measurements. We analyze the amplification of UDM effects in the spectrum of laser-cooled strontium monohydroxide (SrOH). SrOH is the first and, so far, the only polyatomic molecule to be directly laser cooled to sub-millikelvin temperatures, opening the possibility of long experimental coherence times. Because of the high enhancement factors ($\left|Q_{\mu}\right|\approx10^{3}$), measurements of the $\tilde{X}\left(200\right)\leftrightarrow\tilde{X}\left(03^{1}0\right)$ rovibrational transitions of SrOH in the microwave regime can result in $\sim10^{-17}$ fractional uncertainty in $\delta\mu/\mu$ with one day of integration. Furthermore, ultracold SrOH provides a promising platform for suppressing systematic errors. More complex SrOR radicals with additional vibrational modes arising from larger ligands R could lead to even greater enhancement factors.
Title: | Probing entanglement in a many-body-localized system | |
Authors: | Lukin, Alexander; Rispoli, Matthew; Schittko, Robert; Tai, M. Eric; Kaufman, Adam M.; Choi, Soonwon; Khemani, Vedika; Léonard, Julian; Greiner, Markus | |
Publication: | eprint arXiv:1805.09819 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | Condensed Matter - Quantum Gases, Condensed Matter - Disordered Systems and Neural Networks, Condensed Matter - Statistical Mechanics, Physics - Atomic Physics | |
Bibliographic Code: | 2018arXiv180509819L |
Abstract
An interacting quantum system that is subject to disorder may cease to thermalize due to localization of its constituents, thereby marking the breakdown of thermodynamics. The key to our understanding of this phenomenon lies in the system's entanglement, which is experimentally challenging to measure. We realize such a many-body-localized system in a disordered Bose-Hubbard chain and characterize its entanglement properties through particle fluctuations and correlations. We observe that the particles become localized, suppressing transport and preventing the thermalization of subsystems. Notably, we measure the development of non-local correlations, whose evolution is consistent with a logarithmic growth of entanglement entropy - the hallmark of many-body localization. Our work experimentally establishes many-body localization as a qualitatively distinct phenomenon from localization in non-interacting, disordered systems.
Title: | Geometric Understanding of Deep Learning | |
Authors: | Lei, Na; Luo, Zhongxuan; Yau, Shing-Tung; Xianfeng Gu, David | |
Publication: | eprint arXiv:1805.10451 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | Computer Science - Learning, Statistics - Machine Learning | |
Bibliographic Code: | 2018arXiv180510451L |
Abstract
Deep learning is the mainstream technique for many machine learning tasks, including image recognition, machine translation, speech recognition, and so on. It has outperformed conventional methods in various fields and achieved great successes. Unfortunately, the understanding on how it works remains unclear. It has the central importance to lay down the theoretic foundation for deep learning. In this work, we give a geometric view to understand deep learning: we show that the fundamental principle attributing to the success is the manifold structure in data, namely natural high dimensional data concentrates close to a low-dimensional manifold, deep learning learns the manifold and the probability distribution on it. We further introduce the concepts of rectified linear complexity for deep neural network measuring its learning capability, rectified linear complexity of an embedding manifold describing the difficulty to be learned. Then we show for any deep neural network with fixed architecture, there exists a manifold that cannot be learned by the network. Finally, we propose to apply optimal mass transportation theory to control the probability distribution in the latent space.
Title: | Dipolar Exchange Quantum Logic Gate with Polar Molecules | |
Authors: | Ni, Kang-Kuen; Rosenband, Till; Grimes, David D. | |
Publication: | eprint arXiv:1805.10930 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | Physics - Atomic Physics, Physics - Chemical Physics, Quantum Physics | |
Bibliographic Code: | 2018arXiv180510930N |
Abstract
We propose a two-qubit gate based on dipolar exchange interactions between individually addressable polar molecules in an array of optical dipole traps. Our proposal treats the full Hamiltonian of the $^1\Sigma^+$ molecule NaCs, utilizing a pair of nuclear spin states as storage qubits. A third rotationally excited state with rotation-hyperfine coupling enables switchable dipolar exchange interactions between two molecules to generate an iSWAP gate. All three states are insensitive to external magnetic and electric fields. Impacts on gate fidelity due to coupling to other molecular states, imperfect ground-state cooling, blackbody radiation and vacuum spontaneous emission are small, leading to potential fidelity above $99.99~\%$ in a coherent quantum system that can be scaled by purely optical means.
Title: | Quantum Optics in Maxwell's Fish Eye Lens with Single Atoms and Photons | |
Authors: | Perczel, Janos; Kómar, Péter; Lukin, Mikhail D. | |
Publication: | eprint arXiv:1805.11739 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | Quantum Physics, Physics - Atomic Physics, Physics - Optics | |
Comment: | 20 pages, 7 figures | |
Bibliographic Code: | 2018arXiv180511739P |
Abstract
We investigate the quantum optical properties of Maxwell's two-dimensional fish eye lens at the single-photon and single-atom level. We show that such a system mediates effectively infinite-range dipole-dipole interactions between atomic qubits, which can be used to entangle multiple pairs of distant qubits. We find that the rate of the photon exchange between two atoms, which are detuned from the cavity resonances, is well described by a model, where the photon is focused to a diffraction-limited area during absorption. We consider the effect of losses on the system and study the fidelity of the entangling operation via dipole-dipole interaction. We derive our results analytically using perturbation theory and the Born-Markov approximation and then confirm their validity by numerical simulations. We also discuss how the two-dimensional Maxwell's fish eye lens could be realized experimentally using transformational plasmon optics.
Title: | Measuring Color Memory in a Color Glass Condensate at Electron-Ion Colliders | |
Authors: | Ball, Adam; Pate, Monica; Raclariu, Ana-Maria; Strominger, Andrew; Venugopalan, Raju | |
Publication: | eprint arXiv:1805.12224 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | High Energy Physics - Phenomenology, High Energy Physics - Theory, Nuclear Theory | |
Comment: | 23 pages | |
Bibliographic Code: | 2018arXiv180512224B |
Abstract
The color memory effect is the non-abelian gauge theory analog of the gravitational memory effect, in which the passage of color radiation induces a net relative SU(3) color rotation of a pair of nearby quarks. It is proposed that this effect can be measured in the Regge limit of deeply inelastic scattering at electron-ion colliders.
Title: | Holographic Microscopy with Python and HoloPy | |
Authors: | Barkley, Solomon; Dimiduk, Thomas G.; Fung, Jerome; Kaz, David M.; Manoharan, Vinothan N.; McGorty, Ryan; Perry, Rebecca W.; Wang, Anna | |
Publication: | eprint arXiv:1806.00058 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | Electrical Engineering and Systems Science - Image and Video Processing, Physics - Optics | |
Bibliographic Code: | 2018arXiv180600058B |
Abstract
A holographic microscope captures interference patterns, or holograms, that encode three-dimensional (3D) information about the object being viewed. Computation is essential to extracting that 3D information. By wrapping low-level scattering codes and taking advantage of Python's data analysis ecosystem, HoloPy makes it easy for experimentalists to use modern, sophisticated inference methods to analyze holograms. The resulting data can be used to understand how small particles or microorganisms move and interact. The project illustrates how computational tools can enable experimental methods and new experiments.
Title: | Physical interpretation of the partition function for colloidal clusters | |
Authors: | Klein, Ellen D.; Perry, Rebecca W.; Manoharan, Vinothan N. | |
Publication: | eprint arXiv:1806.00155 | |
Publication Date: | 05/2018 | |
Origin: | ARXIV | |
Keywords: | Condensed Matter - Soft Condensed Matter | |
Bibliographic Code: | 2018arXiv180600155K |
Abstract
Colloidal clusters consist of small numbers of colloidal particles bound by weak, short-range attractions. The equilibrium probability of observing a cluster in a particular geometry is well-described by a statistical mechanical model originally developed for molecules. To explain why this model fits experimental data so well, we derive the partition function classically, with no quantum mechanical considerations. Then, by comparing and contrasting the derivation in particle coordinates with that in center-of-mass coordinates, we physically interpret the terms in the center-of-mass formulation, which is equivalent to the high-temperature partition function for molecules. We discuss, from a purely classical perspective, how and why cluster characteristics such as the symmetry number, moments of inertia, and vibrational frequencies affect the equilibrium probabilities.
Title: | Search for the Exotic Meson X (5568 ) with the Collider Detector at Fermilab | |
Authors: | Aaltonen, T.; Amerio, S.; Amidei, D.;... Franklin, M.;... and 394 coauthors (CDF Collaboration) | |
Publication: | Physical Review Letters, Volume 120, Issue 20, id.202006 (PhRvL Homepage) | |
Publication Date: | 05/2018 | |
Origin: | APS | |
Abstract Copyright: | 2018: authors | |
DOI: | 10.1103/PhysRevLett.120.202006 | |
Bibliographic Code: | 2018PhRvL.120t2006A |
Abstract
A search for the exotic meson X (5568 ) decaying into the B_{s}^{0}π^{±} final state is performed using data corresponding to 9.6 fb^{-1} from p p ¯ collisions at √{s }=1960 GeV recorded by the Collider Detector at Fermilab. No evidence for this state is found and an upper limit of 6.7% at the 95% confidence level is set on the fraction of B_{s}^{0} produced through the X (5568 )→B_{s}^{0}π^{±} process.
Title: | Search for a Structure in the B_{s}^{0}π^{±} Invariant Mass Spectrum with the ATLAS Experiment | |
Authors: | Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... and 2881 coauthors (Atlas Collaboration) | |
Publication: | Physical Review Letters, Volume 120, Issue 20, id.202007 (PhRvL Homepage) | |
Publication Date: | 05/2018 | |
Origin: | APS | |
Abstract Copyright: | 2018: CERN | |
DOI: | 10.1103/PhysRevLett.120.202007 | |
Bibliographic Code: | 2018PhRvL.120t2007A |
Abstract
A search for the narrow structure, X (5568 ), reported by the D0 Collaboration in the decay sequence X →B_{s}^{0}π^{±}, B_{s}^{0}→J /ψ ϕ , is presented. The analysis is based on a data sample recorded with the ATLAS detector at the LHC corresponding to 4.9 fb^{-1} of p p collisions at 7 TeV and 19.5 fb^{-1} at 8 TeV. No significant signal was found. Upper limits on the number of signal events, with properties corresponding to those reported by D0, and on the X production rate relative to B_{s}^{0} mesons, ρ_{X}, were determined at 95% confidence level. The results are N (X )<382 and ρ_{X}<0.015 for B_{s}^{0} mesons with transverse momenta above 10 GeV, and N (X )<356 and ρ_{X}<0.016 for transverse momenta above 15 GeV. Limits are also set for potential B_{s}^{0}π^{±} resonances in the mass range 5550 to 5700 MeV.
Title: | Phonon Networks with Silicon-Vacancy Centers in Diamond Waveguides | |
Authors: | Lemonde, M.-A.; Meesala, S.; Sipahigil, A.; Schuetz, M. J. A.; Lukin, M. D.; Loncar, M.; Rabl, P. | |
Publication: | Physical Review Letters, Volume 120, Issue 21, id.213603 (PhRvL Homepage) | |
Publication Date: | 05/2018 | |
Origin: | APS | |
Abstract Copyright: | 2018: American Physical Society | |
DOI: | 10.1103/PhysRevLett.120.213603 | |
Bibliographic Code: | 2018PhRvL.120u3603L |
Abstract
We propose and analyze a novel realization of a solid-state quantum network, where separated silicon-vacancy centers are coupled via the phonon modes of a quasi-one-dimensional diamond waveguide. In our approach, quantum states encoded in long-lived electronic spin states can be converted into propagating phonon wave packets and be reabsorbed efficiently by a distant defect center. Our analysis shows that under realistic conditions, this approach enables the implementation of high-fidelity, scalable quantum communication protocols within chip-scale spin-qubit networks. Apart from quantum information processing, this setup constitutes a novel waveguide QED platform, where strong-coupling effects between solid-state defects and individual propagating phonons can be explored at the quantum level.
Title: | Tunneling topological vacua via extended operators: (Spin-)TQFT spectra and boundary deconfinement in various dimensions | |
Authors: | Wang, Juven; Ohmori, Kantaro; Putrov, Pavel; Zheng, Yunqin; Wan, Zheyan; Guo, Meng; Lin, Hai; Gao, Peng; Yau, Shing-Tung | |
Publication: | Progress of Theoretical and Experimental Physics, Volume 2018, Issue 5, id.053A01 (OUP Homepage) | |
Publication Date: | 05/2018 | |
Origin: | OUP | |
Abstract Copyright: | The Author(s) 2018. Published by Oxford University Press on behalf of the Physical Society of Japan. | |
DOI: | 10.1093/ptep/pty051 | |
Bibliographic Code: | 2018PTEP.2018e3A01W |
Abstract
Distinct quantum vacua of topologically ordered states can be tunneled into each other via extended operators. The possible applications include condensed matter and quantum cosmology. We present a straightforward approach to calculate the partition function on various manifolds and ground state degeneracy (GSD), mainly based on continuum/cochain topological quantum field theories (TQFTs), in any dimension. This information can be related to the counting of extended operators of bosonic/fermionic TQFTs. On the lattice scale, anyonic particles/strings live at the ends of line/surface operators. Certain systems in different dimensions are related to each other through dimensional reduction schemes, analogous to (de)categorification. Examples include spin TQFTs derived from gauging the interacting fermionic symmetry-protected topological states (with fermion parity {Z}_2^f) of symmetry groups {Z}_4× {Z}_2 and ({Z}_4)^2 in 3+1D, also {Z}_2 and ({Z}_2)^2 in 2+1D. Gauging the last three cases begets non-Abelian spin TQFTs (fermionic topological order). We consider situations where a TQFT lives on (1) a closed spacetime or (2) a spacetime with a boundary, such that the bulk and boundary are fully gapped and short- or long-range entangled (SRE/LRE). Anyonic excitations can be deconfined on the boundary. We introduce new exotic topological interfaces on which neither particle nor string excitations alone condense, but only fuzzy-composite objects of extended operators can end (e.g., a string-like composite object formed by a set of particles can end on a special 2+1D boundary of 3+1D bulk). We explore the relations between group extension constructions and partially breaking constructions (e.g., 0-form/higher-form/"composite" breaking) of topological boundaries, after gauging. We comment on the implications of entanglement entropy for some such LRE systems.
Title: | Building one molecule from a reservoir of two atoms | |
Authors: | Liu, L. R.; Hood, J. D.; Yu, Y.; Zhang, J. T.; Hutzler, N. R.; Rosenband, T.; Ni, K.-K. | |
Publication: | Science, Volume 360, Issue 6391, pp. 900-903 (2018). (Sci Homepage) | |
Publication Date: | 05/2018 | |
Category: | CHEMISTRY; PHYSICS | |
Origin: | SCIENCE | |
Abstract Copyright: | (c) 2018: Science | |
DOI: | 10.1126/science.aar7797 | |
Bibliographic Code: | 2018Sci...360..900L |
Abstract
Chemical reactions typically proceed via stochastic encounters between reactants. Going beyond this paradigm, we combined exactly two atoms in a single, controlled reaction. The experimental apparatus traps two individual laser-cooled atoms [one sodium (Na) and one cesium (Cs)] in separate optical tweezers and then merges them into one optical dipole trap. Subsequently, photoassociation forms an excited-state NaCs molecule. The discovery of previously unseen resonances near the molecular dissociation threshold and measurement of collision rates are enabled by the tightly trapped ultracold sample of atoms. As laser-cooling and trapping capabilities are extended to more elements, the technique will enable the study of more diverse, and eventually more complex, molecules in an isolated environment, as well as synthesis of designer molecules for qubits.
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