# Faculty Publications: June, 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.

 Title: The Titan Haze Simulation Experiment: Latest Laboratory Results and Dedicated Plasma Chemistry Model Authors: Sciamma-O'Brien, Ella; Raymond, Alexander; Mazur, Eric; Salama, Farid Publication: American Astronomical Society, AAS Meeting #232, id. 217.10 Publication Date: 06/2018 Origin: AAS Abstract Copyright: (c) 2018: American Astronomical Society Bibliographic Code: 2018AAS...23221710S

### Abstract

Here, we present the latest results on the gas and solid phase analyses in the Titan Haze Simulation (THS) experiment. The THS experiment, developed at NASA Ames’ COSmIC facility is a unique experimental platform that allows us to simulate Titan’s complex atmospheric chemistry at Titan-like temperature (200 K) by cooling down N2-CH4-based mixtures in a supersonic expansion before inducing the chemistry by plasma.Gas phase: The residence time of the jet-accelerated gas in the active plasma region is less than 4 µs, which results in a truncated chemistry enabling us to control how far in the chain of reactions the chemistry is processing. By adding heavier molecules in the initial gas mixture, it is then possible to study the first and intermediate steps of Titan’s atmospheric chemistry as well as specific chemical pathways, as demonstrated by mass spectrometry and comparison to Cassini CAPS data [1]. A new model was recently developed to simulate the plasma chemistry in the THS. Calculated mass spectra produced by this model are in good agreement with the experimental THS mass spectra, confirming that the short residence time in the plasma cavity limits the growth of larger species [2].Solid phase: Scanning electron microscopy and infrared spectroscopy have been used to investigate the effect of the initial gas mixture on the morphology of the THS Titan aerosol analogs as well as on the level and nature of the nitrogen incorporation into these aerosols. A comparison to Cassini VIMS observational data has shown that the THS aerosols produced in simpler mixtures, i.e., that contain more nitrogen and where the N-incorporation is in isocyanide-type molecules instead of nitriles, are more representative of Titan’s aerosols [3]. In addition, a new optical constant facility has been developed at NASA Ames that allows us to determine the complex refractive indices of THS Titan aerosol analogs from NIR to FIR (0.76-222 cm-1). The facility and preliminary results will be presented.References:[1] Sciamma-O'Brien E., et al., Icarus, 243, 325 (2014)[2] Raymond, A., et al., ApJ., 853, 107 (2018)[3] Sciamma-O'Brien E., et al., Icarus, 289, 214 (2017)Acknowledgements: This research is supported by the SSW Program of NASA SMD.

 Title: The Complete Light-curve Sample of Spectroscopically Confirmed SNe Ia from Pan-STARRS1 and Cosmological Constraints from the Combined Pantheon Sample Authors: Scolnic, D. M.; Jones, D. O.; Rest, A.; Pan, Y. C.; Chornock, R.; Foley, R. J.; Huber, M. E.; Kessler, R.; Narayan, G.; Riess, A. G.; Rodney, S.; Berger, E.; Brout, D. J.; Challis, P. J.; Drout, M.; Finkbeiner, D.; Lunnan, R.; Kirshner, R. P.; Sanders, N. E.; Schlafly, E.; Smartt, S.; Stubbs, C. W.; Tonry, J.; Wood-Vasey, W. M.; Foley, M.; Hand, J.; Johnson, E.; Burgett, W. S.; Chambers, K. C.; Draper, P. W.; Hodapp, K. W.; Kaiser, N.; Kudritzki, R. P.; Magnier, E. A.; Metcalfe, N.; Bresolin, F.; Gall, E.; Kotak, R.; McCrum, M.; Smith, K. W. Publication: The Astrophysical Journal, Volume 859, Issue 2, article id. 101, 28 pp. (2018). (ApJ Homepage) Publication Date: 06/2018 Origin: IOP Astronomy Keywords: cosmology: observations, dark energy, supernovae: general DOI: 10.3847/1538-4357/aab9bb Bibliographic Code: 2018ApJ...859..101S

### Abstract

We present optical light curves, redshifts, and classifications for 365 spectroscopically confirmed Type Ia supernovae (SNe Ia) discovered by the Pan-STARRS1 (PS1) Medium Deep Survey. We detail improvements to the PS1 SN photometry, astrometry, and calibration that reduce the systematic uncertainties in the PS1 SN Ia distances. We combine the subset of 279 PS1 SNe Ia (0.03 < z < 0.68) with useful distance estimates of SNe Ia from the Sloan Digital Sky Survey (SDSS), SNLS, and various low-z and Hubble Space Telescope samples to form the largest combined sample of SNe Ia, consisting of a total of 1048 SNe Ia in the range of 0.01 < z < 2.3, which we call the “Pantheon Sample.” When combining Planck 2015 cosmic microwave background (CMB) measurements with the Pantheon SN sample, we find {{{Ω }}}m=0.307+/- 0.012 and w=-1.026+/- 0.041 for the wCDM model. When the SN and CMB constraints are combined with constraints from BAO and local H 0 measurements, the analysis yields the most precise measurement of dark energy to date: {w}0=-1.007+/- 0.089 and {w}a=-0.222+/- 0.407 for the {w}0{w}aCDM model. Tension with a cosmological constant previously seen in an analysis of PS1 and low-z SNe has diminished after an increase of 2× in the statistics of the PS1 sample, improved calibration and photometry, and stricter light-curve quality cuts. We find that the systematic uncertainties in our measurements of dark energy are almost as large as the statistical uncertainties, primarily due to limitations of modeling the low-redshift sample. This must be addressed for future progress in using SNe Ia to measure dark energy.

 Title: Numerical study of the chiral $\mathbb{Z}_3$ quantum phase transition in one spatial dimension Authors: Samajdar, Rhine; Choi, Soonwon; Pichler, Hannes; Lukin, Mikhail D.; Sachdev, Subir Publication: eprint arXiv:1806.01867 Publication Date: 06/2018 Origin: ARXIV Keywords: Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Quantum Gases, Condensed Matter - Statistical Mechanics, Physics - Atomic Physics Comment: 14 pages, 9 figures Bibliographic Code: 2018arXiv180601867S

### Abstract

Recent experiments on a one-dimensional chain of trapped alkali atoms [arXiv:1707.04344] have observed a quantum transition associated with the onset of period-3 ordering of pumped Rydberg states. This spontaneous $\mathbb{Z}_3$ symmetry breaking is described by a constrained model of hard-core bosons proposed by Fendley $et\, \,al.$ [arXiv:cond-mat/0309438]. By symmetry arguments, the transition is expected to be in the universality class of the $\mathbb{Z}_3$ chiral clock model with parameters preserving both time-reversal and spatial-inversion symmetries. We study the nature of the order-disorder transition in these models, and numerically calculate its critical exponents with exact diagonalization and density-matrix renormalization group techniques. We use finite-size scaling to determine the dynamical critical exponent $z$ and the correlation length exponent $\nu$. Our analysis presents the only known instance of a strongly-coupled transition between gapped states with $z \ne 1$, implying an underlying nonconformal critical field theory.

 Title: Triangular antiferromagnetism on the honeycomb lattice of twisted bilayer graphene Authors: Thomson, Alex; Chatterjee, Shubhayu; Sachdev, Subir; Scheurer, Mathias S. Publication: eprint arXiv:1806.02837 Publication Date: 06/2018 Origin: ARXIV Keywords: Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Superconductivity Comment: 18 pages (single column), 12 page appendix, 5 figures, 1 table (added in v2) - v2: Some comments and references and the added table Bibliographic Code: 2018arXiv180602837T

### Abstract

We present the electronic band structures of states with the same symmetry as the three-sublattice planar antiferromagnetic order of the triangular lattice. Such states can also be defined on the honeycomb lattice provided the spin density waves lie on the bonds. We identify cases which are consistent with observations on twisted bilayer graphene: a correlated insulator with an energy gap, yielding a single doubly-degenerate Fermi surface upon hole doping. We also discuss extensions to metallic states which preserve spin rotation invariance, with fluctuating spin density waves and bulk $\mathbb{Z}_2$ topological order.

 Title: Topological Materials Discovery By Large-order symmetry indicators Authors: Tang, Feng; Po, Hoi Chun; Vishwanath, Ashvin; Wan, Xiangang Publication: eprint arXiv:1806.04128 Publication Date: 06/2018 Origin: ARXIV Keywords: Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science Bibliographic Code: 2018arXiv180604128T

### Abstract

Crystalline symmetries play an important role in the classification of band structures, and the rich variety of spatial symmetries in solids leads to various topological crystalline phases (TCPs). However, compared with topological insulators and Dirac/Weyl semimetals, relatively few realistic materials candidates have been proposed for TCPs. Based on our recently developed method for the efficient discovery of topological materials using symmetry indicators, we explore topological materials in five space groups (i.e. SGs87,140,221,191,194), which are indexed by large order strong symmetry based indicators (Z8 and Z12) allowing for the realization of several kinds of gapless boundary states in a single compound. We predict many TCPs, and the representative materials include: Pt3Ge(SG140), graphite(SG194), XPt3 (SG221,X=Sn,Pb), Au4Ti (SG87) and Ti2Sn (SG194). As by-products, we also find that AgXF3 (SG140,X=Rb,Cs) and AgAsX (SG194,X=Sr,Ba) are good Dirac semimetals with clean Fermi surface. The proposed materials provide a good platform to study the novel properties emerging from the interplay between different types of boundary states.

 Title: Meson formation in mixed-dimensional t-J models Authors: Grusdt, Fabian; Zhu, Zheng; Shi, Tao; Demler, Eugene Publication: eprint arXiv:1806.04426 Publication Date: 06/2018 Origin: ARXIV Keywords: Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Quantum Gases, High Energy Physics - Theory, Quantum Physics Comment: 7 pages, 6 figures, 4 pages methods section Bibliographic Code: 2018arXiv180604426G

### Abstract

Surprising properties of doped Mott insulators are at the heart of many quantum materials, including transition metal oxides and organic materials. The key to unraveling complex phenomena observed in these systems lies in understanding the interplay of spin and charge degrees of freedom. One of the most debated questions concerns the nature of charge carriers in a background of fluctuating spins. To shed new light on this problem, we suggest a simplified model with mixed dimensionality, where holes move through a Mott insulator unidirectionally while spin exchange interactions are two dimensional. By studying individual holes in this system, we find direct evidence for the formation of mesonic bound states of holons and spinons, connected by a string of displaced spins -- a precursor of the spin-charge separation obtained in the 1D limit of the model. Our predictions can be tested using ultracold atoms in a quantum gas microscope, allowing to directly image spinons and holons, and reveal the short-range hidden string order which we predict in this model.

 Title: High-fidelity control and entanglement of Rydberg atom qubits Authors: Levine, Harry; Keesling, Alexander; Omran, Ahmed; Bernien, Hannes; Schwartz, Sylvain; Zibrov, Alexander S.; Endres, Manuel; Greiner, Markus; Vuletić, Vladan; Lukin, Mikhail D. Publication: eprint arXiv:1806.04682 Publication Date: 06/2018 Origin: ARXIV Keywords: Quantum Physics, Condensed Matter - Quantum Gases, Physics - Atomic Physics Comment: 9 pages, 4 figures Bibliographic Code: 2018arXiv180604682L

### Abstract

Individual neutral atoms excited to Rydberg states are a promising platform for quantum simulation and quantum information processing. However, experimental progress to date has been limited by short coherence times and relatively low gate fidelities associated with such Rydberg excitations. We report progress towards high-fidelity quantum control of Rydberg atom qubits. Enabled by a reduction in laser phase noise, our approach yields a significant improvement in coherence properties of individual qubits. We further show that this high-fidelity control extends to the multi-particle case by preparing a two-atom entangled state with a fidelity exceeding 0.97(3), and extending its lifetime with a two-atom dynamical decoupling protocol. These advances open up new prospects for scalable quantum simulation and quantum computation with neutral atoms.

 Title: Pressure dependence of the magic twist angle in graphene superlattices Authors: Carr, Stephen; Fang, Shiang; Jarillo-Herrero, Pablo; Kaxiras, Efthimios Publication: eprint arXiv:1806.05078 Publication Date: 06/2018 Origin: ARXIV Keywords: Condensed Matter - Mesoscale and Nanoscale Physics Comment: 6 pages, 4 figures Bibliographic Code: 2018arXiv180605078C

### Abstract

The recently demonstrated unconventional superconductivity in twisted bilayer graphene (tBLG) opens the possibility for interesting applications of two-dimensional layers that involve correlated electron states. Here we explore the possibility of modifying electronic correlations by the application of uniaxial pressure on the weakly interacting layers, which results in increased interlayer coupling and a modification of the magic angle value and associated density of states. Our findings are based on first-principles calculations that accurately describe the height-dependent interlayer coupling through the combined use of Density Functional Theory and Maximally localized Wannier functions. We obtain the relationship between twist angle and external pressure for the magic angle flat bands of tBLG. This may provide a convenient method to tune electron correlations by controlling the length scale of the superlattice.

 Title: Measuring the Local Twist Angle and Layer Arrangement in Van der Waals Heterostructures Authors: de Jong, Tobias A.; Jobst, Johannes; Yoo, Hyobin; Krasovskii, Eugene E.; Kim, Philip; van der Molen, Sense Jan Publication: eprint arXiv:1806.05155 Publication Date: 06/2018 Origin: ARXIV Keywords: Condensed Matter - Materials Science Bibliographic Code: 2018arXiv180605155D

### Abstract

The properties of Van der Waals heterostructures are determined by the twist angle and the interface between adjacent layers as well as their polytype and stacking. Here we describe the use of spectroscopic Low Energy Electron Microscopy (LEEM) and micro Low Energy Electron Diffraction ({\mu}LEED) methods to measure these properties locally. We present results on a MoS$_{2}$/hBN heterostructure, but the methods are applicable to other materials. Diffraction spot analysis is used to assess the benefits of using hBN as a substrate. In addition, by making use of the broken rotational symmetry of the lattice, we determine the cleaving history of the MoS$_{2}$ flake, i.e., which layer stems from where in the bulk.

 Title: Active colloidal particles in emulsion droplets: A model system for the cytoplasm Authors: Horowitz, Viva R.; Chambers, Zachary C.; Gözen, İrep; Dimiduk, Thomas G.; Manoharan, Vinothan N. Publication: eprint arXiv:1806.05760 Publication Date: 06/2018 Origin: ARXIV Keywords: Condensed Matter - Soft Condensed Matter Bibliographic Code: 2018arXiv180605760H

### Abstract

In living cells, molecular motors create activity that enhances the diffusion of particles throughout the cytoplasm, and not just ones attached to the motors. We demonstrate initial steps toward creating artificial cells that mimic this phenomenon. Our system consists of active, Pt-coated Janus particles and passive tracers confined to emulsion droplets. We track the motion of both the active particles and passive tracers in a hydrogen peroxide solution, which serves as the fuel to drive the motion. We first show that correcting for bulk translational and rotational motion of the droplets induced by bubble formation is necessary to accurately track the particles. After drift correction, we find that the active particles show enhanced diffusion in the interior of the droplets and are not captured by the droplet interface. At the particle and hydrogen peroxide concentrations we use, we observe little coupling between the active and passive particles. We discuss the possible reasons for lack of coupling and describe ways to improve the system to more effectively mimic cytoplasmic activity.

 Title: Long-Lived Particles at the Energy Frontier: The MATHUSLA Physics Case Authors: Curtin, David; Drewes, Marco; McCullough, Matthew;... Reece, Matthew;... and 84 coauthors Publication: eprint arXiv:1806.07396 Publication Date: 06/2018 Origin: ARXIV Keywords: High Energy Physics - Phenomenology, High Energy Physics - Experiment Comment: 208 pages, 72 figures Bibliographic Code: 2018arXiv180607396C

### Abstract

We examine the theoretical motivations for long-lived particle (LLP) signals at the LHC in a comprehensive survey of Standard Model (SM) extensions. LLPs are a common prediction of a wide range of theories that address unsolved fundamental mysteries such as naturalness, dark matter, baryogenesis and neutrino masses, and represent a natural and generic possibility for physics beyond the SM (BSM). In most cases the LLP lifetime can be treated as a free parameter from the $\mu$m scale up to the Big Bang Nucleosynthesis limit of $\sim 10^7$m. Neutral LLPs with lifetimes above $\sim$ 100m are particularly difficult to probe, as the sensitivity of the LHC main detectors is limited by challenging backgrounds, triggers, and small acceptances. MATHUSLA is a proposal for a minimally instrumented, large-volume surface detector near ATLAS or CMS. It would search for neutral LLPs produced in HL-LHC collisions by reconstructing displaced vertices (DVs) in a low-background environment, extending the sensitivity of the main detectors by orders of magnitude in the long-lifetime regime. In this white paper we study the LLP physics opportunities afforded by a MATHUSLA-like detector at the HL-LHC. We develop a model-independent approach to describe the sensitivity of MATHUSLA to BSM LLP signals, and compare it to DV and missing energy searches at ATLAS or CMS. We then explore the BSM motivations for LLPs in considerable detail, presenting a large number of new sensitivity studies. While our discussion is especially oriented towards the long-lifetime regime at MATHUSLA, this survey underlines the importance of a varied LLP search program at the LHC in general. By synthesizing these results into a general discussion of the top-down and bottom-up motivations for LLP searches, it is our aim to demonstrate the exceptional strength and breadth of the physics case for the construction of the MATHUSLA detector.

 Title: Compactifications of ADE conformal matter on a torus Authors: Kim, Hee-Cheol; Razamat, Shlomo S.; Vafa, Cumrun; Zafrir, Gabi Publication: eprint arXiv:1806.07620 Publication Date: 06/2018 Origin: ARXIV Keywords: High Energy Physics - Theory Comment: 66 pages; 38 figures Bibliographic Code: 2018arXiv180607620K

### Abstract

In this paper we study compactifications of ADE type conformal matter, N M5 branes probing ADE singularity, on torus with flux for global symmetry. We systematically construct the four dimensional theories by first going to five dimensions and studying interfaces. We claim that certain interfaces can be associated with turning on flux in six dimensions. The interface models when compactified on a circle comprise building blocks for constructing four dimensional models associated to flux compactifications of six dimensional theories on a torus. The theories in four dimensions turn out to be quiver gauge theories and the construction implies many interesting cases of IR symmetry enhancements and dualities of such theories.

 Title: Band Structure of Twisted Bilayer Graphene: Emergent Symmetries, Commensurate Approximants and Wannier Obstructions Authors: Zou, Liujun; Po, Hoi Chun; Vishwanath, Ashvin; Senthil, T. Publication: eprint arXiv:1806.07873 Publication Date: 06/2018 Origin: ARXIV Keywords: Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science Comment: 14 pages + appendices; v2: references updated and typos fixed Bibliographic Code: 2018arXiv180607873Z

### Abstract

A remarkable feature of the band structure of bilayer graphene at small twist angle is the appearance of isolated bands near neutrality, whose bandwidth can be reduced at certain magic angles (eg. $\theta\sim 1.05^\circ$). In this regime, correlated insulating states and superconductivity have been experimentally observed. A microscopic description of these phenomena requires an understanding of universal aspects of the band structure, which we discuss here. First, we point out the importance of emergent symmetries, such as valley conservation, which are excellent symmetries in the limit of small twist angles and dictate qualitative features of the band structure. These have sometimes been overlooked when discussing commensurate approximants to the band structure, which we also review here, and solidify their connection with the continuum theory which incorporates all emergent symmetries. Finally, we discuss obstructions to writing down tight-binding models of just the isolated bands, and in particular a new symmetry based diagnostic of these obstructions, as well as relations to band topology and strategies for resolving the obstruction.

 Title: Data-driven studies of magnetic two-dimensional materials Authors: Rhone, Trevor David; Chen, Wei; Desai, Shaan; Yacoby, Amir; Kaxiras, Efthimios Publication: eprint arXiv:1806.07989 Publication Date: 06/2018 Origin: ARXIV Keywords: Condensed Matter - Materials Science Bibliographic Code: 2018arXiv180607989R

### Abstract

We use a data-driven approach to study the magnetic and thermodynamic properties of van der Waals (vdW) layered materials. We investigate monolayers of the form A$_2$B$_2$X$_6$, based on the known material Cr$_2$Ge$_2$Te$_6$, using density functional theory (DFT) calculations and machine learning methods to determine their magnetic properties, such as magnetic order and magnetic moment. We also examine formation energies and use them as a proxy for chemical stability. We show that machine learning tools, combined with DFT calculations, can provide a computationally efficient means to predict properties of such two-dimensional (2D) magnetic materials. Our data analytics approach provides insights into the microscopic origins of magnetic ordering in these systems. For instance, we find that the X site strongly affects the magnetic coupling between neighboring A sites, which drives the magnetic ordering. Our approach opens new ways for rapid discovery of chemically stable vdW materials that exhibit magnetic behavior.

 Title: De Sitter Space and the Swampland Authors: Obied, Georges; Ooguri, Hirosi; Spodyneiko, Lev; Vafa, Cumrun Publication: eprint arXiv:1806.08362 Publication Date: 06/2018 Origin: ARXIV Keywords: High Energy Physics - Theory Comment: 22 pages, 1 table; added references Bibliographic Code: 2018arXiv180608362O

### Abstract

It has been notoriously difficult to construct a meta-stable de Sitter (dS) vacuum in string theory in a controlled approximation. This suggests the possibility that meta-stable dS belongs to the swampland. In this paper, we propose a swampland criterion in the form of $|\nabla V|\geq\ c \cdot V$ for a scalar potential $V$ of any consistent theory of quantum gravity, for a positive constant $c$. In particular, this bound forbids dS vacua. The existence of this bound is motivated by the abundance of string theory constructions and no-go theorems which exhibit this behavior. We also extend some of the well-known no-go theorems for the existence of dS vacua in string theory to more general accelerating universes and reinterpret the results in terms of restrictions on allowed scalar potentials.

 Title: Implementation of a stable, high-power optical lattice for quantum gas microscopy Authors: Mazurenko, A.; Blatt, S.; Huber, F.; Parsons, M. F.; Chiu, C. S.; Ji, G.; Greif, D.; Greiner, M. Publication: eprint arXiv:1806.08997 Publication Date: 06/2018 Origin: ARXIV Keywords: Condensed Matter - Quantum Gases, Physics - Atomic Physics, Quantum Physics Comment: 13 pages, 14 figures Bibliographic Code: 2018arXiv180608997M

### Abstract

We describe the design and implementation of a stable high-power 1064 nm laser system to generate optical lattices for experiments with ultracold quantum gases. The system is based on a low-noise laser amplified by an array of four heavily modified, high-power fiber amplifiers. The beam intensity is stabilized and controlled with a nonlinear feedback loop. Using real-time monitoring of the resulting optical lattice, we find the stability of the lattice site positions to be well below the lattice spacing for several hours. The pointing stability of the optical lattice beams is around one lattice spacing and the long-term (six month) relative stability of the lattice spacing itself is 0.5% RMS.

 Title: Clockwork Axions in Cosmology: Is Chromonatural Inflation Chrononatural? Authors: Agrawal, Prateek; Fan, JiJi; Reece, Matthew Publication: eprint arXiv:1806.09621 Publication Date: 06/2018 Origin: ARXIV Keywords: High Energy Physics - Theory, Astrophysics - Cosmology and Nongalactic Astrophysics, High Energy Physics - Phenomenology Bibliographic Code: 2018arXiv180609621A

### Abstract

Many cosmological models rely on large couplings of axions to gauge fields. Examples include theories of magnetogenesis, inflation on a steep potential, chiral gravitational waves, and chromonatural inflation. Such theories require a mismatch between the axion field range and the mass scale appearing in the $a F \widetilde{F}$ coupling. This mismatch suggests an underlying monodromy, with the axion winding around its fundamental period a large number of times. We investigate the extent to which this integer can be explained as a product of smaller integers in a UV completion: in the parlance of our times, can the theory be "clockworked"? We argue that a clockwork construction producing a potential $\mu^4 \cos(\frac{a}{j F_a})$ for an axion of fundamental period $F_a$ will obey the constraint $\mu < F_a$. For some applications, including chromonatural inflation with sub-Planckian field range, this constraint obstructs a clockwork UV completion. Alternative routes to a large coupling include fields of large charge (an approach limited by strong coupling) or kinetic mixing (requiring a lighter axion). Our results suggest that completions of axion cosmologies that explain the large parameter in the theory potentially alter the phenomenological predictions of the model.

 Title: Full Commuting Projector Hamiltonians of Interacting Symmetry-Protected Topological Phases of Fermions Authors: Tantivasadakarn, Nathanan; Vishwanath, Ashvin Publication: eprint arXiv:1806.09709 Publication Date: 06/2018 Origin: ARXIV Keywords: Condensed Matter - Strongly Correlated Electrons Comment: 20 pages. 8 figures Bibliographic Code: 2018arXiv180609709T

### Abstract

Using the decorated domain wall procedure, we construct Finite Depth Local Unitaries (FDLUs) that realize Fermionic Symmetry-Protected Topological (SPT) phases. This results in explicit full' commuting projector Hamiltonians, where full' implies the fact that the ground state, as well as all excited state of these Hamiltonians realize the nontrivial SPT phase. We begin by constructing explicit examples of 1+1D phases protected by symmetry groups $G=\mathbb Z_2^T \times \mathbb Z_2^F$ , which also has a free fermion realization in class BDI, and $G=\mathbb Z_4 \times \mathbb Z_4^F$, which does not. We then turn to 2+1D, and construct the square roots of the Levin-Gu bosonic SPT phase, protected by $\mathbb Z_2 \times \mathbb Z_2^F$ symmetry, in a concrete model of fermions and spins on the triangular lattice. Edge states and the anomalous symmetry action on them are explicitly derived. Although this phase has a free fermion representation, as two copies of $p+ip$ superconductors combined with their $p-ip$ counterparts with a different symmetry charge, the full set of commuting projectors is only realized in the strongly interacting version, which also implies that it admits a many-body localized realization.

 Title: On the Cosmological Implications of the String Swampland Authors: Agrawal, Prateek; Obied, Georges; Steinhardt, Paul J.; Vafa, Cumrun Publication: eprint arXiv:1806.09718 Publication Date: 06/2018 Origin: ARXIV Keywords: High Energy Physics - Theory, Astrophysics - Cosmology and Nongalactic Astrophysics, General Relativity and Quantum Cosmology, High Energy Physics - Phenomenology Comment: 7 pages, 1 figure Bibliographic Code: 2018arXiv180609718A

### Abstract

We study constraints imposed by two proposed string Swampland criteria on cosmology. These criteria involve an upper bound on the range traversed by scalar fields as well as a lower bound on $|\nabla_{\phi} V|/V$ when $V >0$. We find that inflationary models are generically in tension with these two criteria. Applying these same criteria to dark energy in the present epoch, we find that specific quintessence models can satisfy these bounds and, at the same time, satisfy current observational constraints. Assuming the two Swampland criteria are valid, we argue that the universe will undergo a phase transition within a few Hubble times. These criteria sharpen the motivation for future measurements of the tensor-to-scalar ratio $r$ and the dark energy equation of state $w$, and for tests of the equivalence principle for dark matter.

 Title: Probing quantum thermalization of a disordered dipolar spin ensemble with discrete time-crystalline order Authors: Choi, Joonhee; Zhou, Hengyun; Choi, Soonwon; Landig, Renate; Ho, Wen Wei; Isoya, Junichi; Jelezko, Fedor; Onoda, Shinobu; Sumiya, Hitoshi; Abanin, Dmitry A.; Lukin, Mikhail D. Publication: eprint arXiv:1806.10169 Publication Date: 06/2018 Origin: ARXIV Keywords: Quantum Physics, Condensed Matter - Disordered Systems and Neural Networks, Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Statistical Mechanics, Physics - Atomic Physics Comment: 6 + 14 pages, 4 + 8 figures Bibliographic Code: 2018arXiv180610169C

### Abstract

We investigate thermalization dynamics of a driven dipolar many-body quantum system through the stability of discrete time crystalline order. Using periodic driving of electronic spin impurities in diamond, we realize different types of interactions between spins and demonstrate experimentally that the interplay of disorder, driving and interactions leads to several qualitatively distinct regimes of thermalization. For short driving periods, the observed dynamics are well described by an effective Hamiltonian which sensitively depends on interaction details. For long driving periods, the system becomes susceptible to energy exchange with the driving field and eventually enters a universal thermalizing regime, where the dynamics can be described by interaction-induced dephasing of individual spins. Our analysis reveals important differences between thermalization of long-range Ising and other dipolar spin models.

 Title: D-type fiber-base duality Authors: Haghighat, Babak; Kim, Joonho; Yan, Wenbin; Yau, Shing-Tung Publication: eprint arXiv:1806.10335 Publication Date: 06/2018 Origin: ARXIV Keywords: High Energy Physics - Theory Comment: 34 pages, 5 figures Bibliographic Code: 2018arXiv180610335H

### Abstract

M5 branes probing D-type singularities give rise to 6d (1,0) SCFTs with $SO \times SO$ flavor symmetry known as D-type conformal matter theories. Gauging the diagonal $SO$-flavor symmetry leads to a little string theory with an intrinsic scale which can be engineered in F-theory by compactifying on a doubly-elliptic Calabi-Yau manifold. We derive Seiberg-Witten curves for these little string theories which can be interpreted as mirror curves for the corresponding Calabi-Yau manifolds. Under fiber-base duality these models are mapped to D-type quiver gauge theories and we check that their Seiberg-Witten curves match. By taking decompactification limits, we construct the curves for the related 6d SCFTs and connect to known results in the literature by further taking 5d and 4d limits.

 Title: Measurement of the inclusive and fiducial t\bar{t} production cross-sections in the lepton+jets channel in pp collisions at √{s} = 8 TeV with the ATLAS detector Authors: Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... ; and 2894 coauthors Publication: The European Physical Journal C, Volume 78, Issue 6, article id. #487, 31 pp. (EPJC Homepage) Publication Date: 06/2018 Origin: SPRINGER Abstract Copyright: (c) 2018: CERN for the benefit of the ATLAS collaboration DOI: 10.1140/epjc/s10052-018-5904-z Bibliographic Code: 2018EPJC...78..487A

### Abstract

The inclusive and fiducial t\bar{t} production cross-sections are measured in the lepton+jets channel using 20.2 fb^{-1} of proton-proton collision data at a centre-of-mass energy of 8 TeV recorded with the ATLAS detector at the LHC. Major systematic uncertainties due to the modelling of the jet energy scale and b-tagging efficiency are constrained by separating selected events into three disjoint regions. In order to reduce systematic uncertainties in the most important background, the W {+ jets} process is modelled using Z+ jets events in a data-driven approach. The inclusive t\bar{t} cross-section is measured with a precision of 5.7% to be σ _{ {inc}}(t\bar{t}) = 248.3 ± 0.7 ({stat.}) ± 13.4 ({syst.}) ± 4.7 ({lumi.}) {pb}, assuming a top-quark mass of 172.5 GeV. The result is in agreement with the Standard Model prediction. The cross-section is also measured in a phase space close to that of the selected data. The fiducial cross-section is σ _{ {fid}}(t\bar{t}) = 48.8 ± 0.1 ({stat.}) ± 2.0 ({syst.}) ± 0.9 ({lumi.}) {pb} with a precision of 4.5%.

 Title: Search for long-lived charginos based on a disappearing-track signature in pp collisions at √{s}=13 TeV with the ATLAS detector Authors: Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... ; and 2867 coauthors Publication: Journal of High Energy Physics, Volume 2018, Issue 6, article id. #22, 48 pp. Publication Date: 06/2018 Origin: SPRINGER Keywords: Hadron-Hadron scattering (experiments) Abstract Copyright: (c) 2018: The Author(s) DOI: 10.1007/JHEP06(2018)022 Bibliographic Code: 2018JHEP...06..022A

### Abstract

This paper presents a search for direct electroweak gaugino or gluino pair production with a chargino nearly mass-degenerate with a stable neutralino. It is based on an integrated luminosity of 36.1 fb-1 of pp collisions at √{s}=13 TeV collected by the ATLAS experiment at the LHC. The final state of interest is a disappearing track accompanied by at least one jet with high transverse momentum from initial-state radiation or by four jets from the gluino decay chain. The use of short track segments reconstructed from the innermost tracking layers significantly improves the sensitivity to short chargino lifetimes. The results are found to be consistent with Standard Model predictions. Exclusion limits are set at 95% confidence level on the mass of charginos and gluinos for different chargino lifetimes. For a pure wino with a lifetime of about 0.2 ns, chargino masses up to 460 GeV are excluded. For the strong production channel, gluino masses up to 1.65 TeV are excluded assuming a chargino mass of 460 GeV and lifetime of 0.2 ns.

 Title: D-type conformal matter and SU/USp quivers Authors: Kim, Hee-Cheol; Razamat, Shlomo S.; Vafa, Cumrun; Zafrir, Gabi Publication: Journal of High Energy Physics, Volume 2018, Issue 6, article id. #58, 37 pp. Publication Date: 06/2018 Origin: SPRINGER Keywords: Supersymmetric Gauge Theory, Duality in Gauge Field Theories, Supersymmetry and Duality, Gauge Symmetry Abstract Copyright: (c) 2018: The Author(s) DOI: 10.1007/JHEP06(2018)058 Bibliographic Code: 2018JHEP...06..058K

### Abstract

We discuss the four dimensional models obtained by compactifying a single M5 brane probing D N singularity (minimal D-type (1 , 0) conformal matter in six dimensions) on a torus with flux for abelian subgroups of the SO(4 N) flavor symmetry. We derive the resulting quiver field theories in four dimensions by first compactifying on a circle and relating the flux to duality domain walls in five dimensions. This leads to novel N=1 dualities in 4 dimensions which arise from distinct five dimensional realizations of the circle compactifications of the D-type conformal matter.

 Title: Light, the universe and everything - 12 Herculean tasks for quantum cowboys and black diamond skiers Authors: Agarwal, Girish; Allen, Roland E.; Bezděková, Iva; Boyd, Robert W.; Chen, Goong; Hanson, Ronald; Hawthorne, Dean L.; Hemmer, Philip; Kim, Moochan B.; Kocharovskaya, Olga; Lee, David M.; Lidström, Sebastian K.; Lidström, Suzy; Losert, Harald; Maier, Helmut; Neuberger, John W.; Padgett, Miles J.; Raizen, Mark; Rajendran, Surjeet; Rasel, Ernst; Schleich, Wolfgang P.; Scully, Marlan O.; Shchedrin, Gavriil; Shvets, Gennady; Sokolov, Alexei V.; Svidzinsky, Anatoly; Walsworth, Ronald L.; Weiss, Rainer; Wilczek, Frank; Willner, Alan E.; Yablonovitch, Eli; Zheludev, Nikolay Publication: Journal of Modern Optics, Volume 65, Issue 11, p.1261-1308 Publication Date: 06/2018 Origin: T+F Keywords: Quantum, optics, gravitational waves, LIGO, time crystal, nitrogen-vacancy centres, photonics, laser, free-electron laser, metrology, quantum internet, quantum computing, imaging, topological, non-linear, Bose-Einstein condensate, interferometry, Riemann hypothesis, fractal quantum carpets, Bekenstein-Hawking, equivalence principle, coherence, super-resolution, photon, maser, magnetometer, isotope separation, nanostructure, solar energy, Maxwell's demon, superradiance, sensing, Rayleigh limit, lithography, Lamb shift, Bayesian Abstract Copyright: 2018: Informa UK Limited, trading as Taylor & Francis Group DOI: 10.1080/09500340.2018.1454525 Bibliographic Code: 2018JMOp...65.1261A

### Abstract

The Winter Colloquium on the Physics of Quantum Electronics (PQE) has been a seminal force in quantum optics and related areas since 1971. It is rather mind-boggling to recognize how the concepts presented at these conferences have transformed scientific understanding and human society. In January 2017, the participants of PQE were asked to consider the equally important prospects for the future, and to formulate a set of questions representing some of the greatest aspirations in this broad field. The result is this multi-authored paper, in which many of the world's leading experts address the following fundamental questions: (1) What is the future of gravitational wave astronomy? (2) Are there new quantum phases of matter away from equilibrium that can be found and exploited - such as the time crystal? (3) Quantum theory in uncharted territory: What can we learn? (4) What are the ultimate limits for laser photon energies? (5) What are the ultimate limits to temporal, spatial and optical resolution? (6) What novel roles will atoms play in technology? (7) What applications lie ahead for nitrogen-vacancy centres in diamond? (8) What is the future of quantum coherence, squeezing and entanglement for enhanced super-resolution and sensing? (9) How can we solve (some of) humanity's biggest problems through new quantum technologies? (10) What new understanding of materials and biological molecules will result from their dynamical characterization with free-electron lasers? (11) What new technologies and fundamental discoveries might quantum optics achieve by the end of this century? (12) What novel topological structures can be created and employed in quantum optics?

 Title: Metallic hydrogen Authors: Silvera, Isaac F.; Dias, Ranga Publication: Journal of Physics: Condensed Matter, Volume 30, Issue 25, article id. 254003 (2018). Publication Date: 06/2018 Origin: IOP DOI: 10.1088/1361-648X/aac401 Bibliographic Code: 2018JPCM...30y4003S

### Abstract

Hydrogen is the simplest and most abundant element in the Universe. There are two pathways for creating metallic hydrogen under high pressures. Over 80 years ago Wigner and Huntington predicted that if solid molecular hydrogen was sufficiently compressed in the T  =  0 K limit, molecules would dissociate to form atomic metallic hydrogen (MH). We have observed this transition at a pressure of 4.95 megabars. MH in this form has probably never existed on Earth or in the Universe; it may be a room temperature superconductor and is predicted to be metastable. If metastable it will have an important technological impact. Liquid metallic hydrogen can also be produced at intermediate pressures and high temperatures and is believed to make up ~90% of the planet Jupiter. We have observed this liquid–liquid transition, also known as the plasma phase transition, at pressures of ~1–2 megabar and temperatures ~1000–2000 K. However, in this paper we shall focus on the Wigner–Huntington transition. We shall discuss the methods used to observe metallic hydrogen at extreme conditions of static pressure in the laboratory, extending our understanding of the phase diagram of the simplest atom in the periodic table.

 Title: Geometric constraints during epithelial jamming Authors: Atia, Lior; Bi, Dapeng; Sharma, Yasha; Mitchel, Jennifer A.; Gweon, Bomi; Koehler, Stephan A.; DeCamp, Stephen J.; Lan, Bo; Kim, Jae Hun; Hirsch, Rebecca; Pegoraro, Adrian F.; Lee, Kyu Ha; Starr, Jacqueline R.; Weitz, David A.; Martin, Adam C.; Park, Jin-Ah; Butler, James P.; Fredberg, Jeffrey J. Publication: Nature Physics, Volume 14, Issue 6, p.613-620 Publication Date: 06/2018 Origin: NATURE Abstract Copyright: 2018: The Author(s) DOI: 10.1038/s41567-018-0089-9 Bibliographic Code: 2018NatPh..14..613A

### Abstract

As an injury heals, an embryo develops or a carcinoma spreads, epithelial cells systematically change their shape. In each of these processes cell shape is studied extensively whereas variability of shape from cell to cell is regarded most often as biological noise. But where do cell shape and its variability come from? Here we report that cell shape and shape variability are mutually constrained through a relationship that is purely geometrical. That relationship is shown to govern processes as diverse as maturation of the pseudostratified bronchial epithelial layer cultured from non-asthmatic or asthmatic donors, and formation of the ventral furrow in the Drosophila embryo. Across these and other epithelial systems, shape variability collapses to a family of distributions that is common to all. That distribution, in turn, is accounted for by a mechanistic theory of cell-cell interaction, showing that cell shape becomes progressively less elongated and less variable as the layer becomes progressively more jammed. These findings suggest a connection between jamming and geometry that spans living organisms and inert jammed systems, and thus transcends system details. Although molecular events are needed for any complete theory of cell shape and cell packing, observations point to the hypothesis that jamming behaviour at larger scales of organization sets overriding geometric constraints.

 Title: Publisher Correction: Geometric constraints during epithelial jamming Authors: Atia, Lior; Bi, Dapeng; Sharma, Yasha; Mitchel, Jennifer A.; Gweon, Bomi; Koehler, Stephan A.; DeCamp, Stephen J.; Lan, Bo; Kim, Jae Hun; Hirsch, Rebecca; Pegoraro, Adrian F.; Lee, Kyu Ha; Starr, Jacqueline R.; Weitz, David A.; Martin, Adam C.; Park, Jin-Ah; Butler, James P.; Fredberg, Jeffrey J. Publication: Nature Physics, Volume 14, Issue 6, p.629-629 Publication Date: 06/2018 Origin: NATURE Abstract Copyright: 2018: The Publisher DOI: 10.1038/s41567-018-0139-3 Bibliographic Code: 2018NatPh..14Q.629A

### Abstract

In the version of this Article originally published, the Supplementary Movies were linked to the wrong descriptions. These have now been corrected. Additionally, the authors would like to note that co-authors James P. Butler and Jeffrey J. Fredberg contributed equally to this Article; this change has now been made.

 Title: Author Correction: Geometric constraints during epithelial jamming Authors: Atia, Lior; Bi, Dapeng; Sharma, Yasha; Mitchel, Jennifer A.; Gweon, Bomi; Koehler, Stephan A.; DeCamp, Stephen J.; Lan, Bo; Kim, Jae Hun; Hirsch, Rebecca; Pegoraro, Adrian F.; Lee, Kyu Ha; Starr, Jacqueline R.; Weitz, David A.; Martin, Adam C.; Park, Jin-Ah; Butler, James P.; Fredberg, Jeffrey J. Publication: Nature Physics, Volume 14, Issue 6, p.629-629 Publication Date: 06/2018 Origin: NATURE Abstract Copyright: 2018: The Publisher DOI: 10.1038/s41567-018-0168-y Bibliographic Code: 2018NatPh..14R.629A

### Abstract

In the first correction to this Article, the authors added James P. Butler and Jeffrey J. Fredburg as equally contributing authors. However, this was in error; the statement should have remained indicating that Lior Atia, Dapeng Bi and Yasha Sharma contributed equally. This has now been corrected.

 Title: Charge Diffusion Variations in Pan-STARRS1 CCDs Authors: Magnier, Eugene A.; Tonry, J. L.; Finkbeiner, D.; Schlafly, E.; Burgett, W. S.; Chambers, K. C.; Flewelling, H. A.; Hodapp, K. W.; Kaiser, N.; Kudritzki, R.-P.; Metcalfe, N.; Wainscoat, R. J.; Waters, C. Z. Publication: Publications of the Astronomical Society of the Pacific, Volume 130, Issue 988, pp. 065002 (2018). (PASP Homepage) Publication Date: 06/2018 Origin: IOP DOI: 10.1088/1538-3873/aaaad8 Bibliographic Code: 2018PASP..130f5002M

### Abstract

Thick back-illuminated deep-depletion CCDs have superior quantum efficiency over previous generations of thinned and traditional thick CCDs. As a result, they are being used for wide-field imaging cameras in several major projects. We use observations from the Pan-STARRS 3π survey to characterize the behavior of the deep-depletion devices used in the Pan-STARRS 1 Gigapixel Camera. We have identified systematic spatial variations in the photometric measurements and stellar profiles that are similar in pattern to the so-called “tree rings” identified in devices used by other wide-field cameras (e.g., DECam and Hypersuprime Camera). The tree-ring features identified in these other cameras result from lateral electric fields that displace the electrons as they are transported in the silicon to the pixel location. In contrast, we show that the photometric and morphological modifications observed in the GPC1 detectors are caused by variations in the vertical charge transportation rate and resulting charge diffusion variations.

 Title: Measurement of the production cross section of three isolated photons in pp collisions at √{ s } = 8 TeV using the ATLAS detector Authors: Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... ; and 2843 coauthors Publication: Physics Letters B, Volume 781, p. 55-76. Publication Date: 06/2018 Origin: ELSEVIER Abstract Copyright: (c) 2018 Elsevier Science B.V. All rights reserved. DOI: 10.1016/j.physletb.2018.03.057 Bibliographic Code: 2018PhLB..781...55A

### Abstract

A measurement of the production of three isolated photons in proton-proton collisions at a centre-of-mass energy √{ s } = 8 TeV is reported. The results are based on an integrated luminosity of 20.2 fb-1 collected with the ATLAS detector at the LHC. The differential cross sections are measured as functions of the transverse energy of each photon, the difference in azimuthal angle and in pseudorapidity between pairs of photons, the invariant mass of pairs of photons, and the invariant mass of the triphoton system. A measurement of the inclusive fiducial cross section is also reported. Next-to-leading-order perturbative QCD predictions are compared to the cross-section measurements. The predictions underestimate the measurement of the inclusive fiducial cross section and the differential measurements at low photon transverse energies and invariant masses. They provide adequate descriptions of the measurements at high values of the photon transverse energies, invariant mass of pairs of photons, and invariant mass of the triphoton system.

 Title: Search for W‧ → tb decays in the hadronic final state using pp collisions at √{ s } = 13TeV with the ATLAS detector Authors: Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... ; and 2891 coauthors Publication: Physics Letters B, Volume 781, p. 327-348. Publication Date: 06/2018 Origin: ELSEVIER Abstract Copyright: (c) 2018 Elsevier Science B.V. All rights reserved. DOI: 10.1016/j.physletb.2018.03.036 Bibliographic Code: 2018PhLB..781..327A

### Abstract

A search for W‧-boson production in the W‧ → t b bar → qqbar‧ b b bar decay channel is presented using 36.1fb-1 of 13 TeV proton-proton collision data collected by the ATLAS detector at the Large Hadron Collider in 2015 and 2016. The search is interpreted in terms of both a left-handed and a right-handed chiral W‧ boson within the mass range 1-5 TeV. Identification of the hadronically decaying top quark is performed using jet substructure tagging techniques based on a shower deconstruction algorithm. No significant deviation from the Standard Model prediction is observed and the results are expressed as upper limits on the W‧ → t b bar production cross-section times branching ratio as a function of the W‧-boson mass. These limits exclude W‧ bosons with right-handed couplings with masses below 3.0 TeV and W‧ bosons with left-handed couplings with masses below 2.9 TeV, at the 95% confidence level.

 Title: Coupling two spin qubits with a high-impedance resonator Authors: Harvey, S. P.; Bøttcher, C. G. L.; Orona, L. A.; Bartlett, S. D.; Doherty, A. C.; Yacoby, A. Publication: Physical Review B, Volume 97, Issue 23, id.235409 (PhRvB Homepage) Publication Date: 06/2018 Origin: APS Abstract Copyright: 2018: American Physical Society DOI: 10.1103/PhysRevB.97.235409 Bibliographic Code: 2018PhRvB..97w5409H

### Abstract

Fast, high-fidelity single and two-qubit gates are essential to building a viable quantum information processor, but achieving both in the same system has proved challenging for spin qubits. We propose and analyze an approach to perform a long-distance two-qubit controlled phase (CPHASE) gate between two singlet-triplet qubits using an electromagnetic resonator to mediate their interaction. The qubits couple longitudinally to the resonator, and by driving the qubits near the resonator's frequency, they can be made to acquire a state-dependent geometric phase that leads to a CPHASE gate independent of the initial state of the resonator. Using high impedance resonators enables gate times of order 10 ns while maintaining long coherence times. Simulations show average gate fidelities of over 96% using currently achievable experimental parameters and over 99% using state-of-the-art resonator technology. After optimizing the gate fidelity in terms of parameters tuneable in situ, we find it takes a simple power-law form in terms of the resonator's impedance and quality and the qubits' noise bath.

 Title: Infinite family of three-dimensional Floquet topological paramagnets Authors: Potter, Andrew C.; Vishwanath, Ashvin; Fidkowski, Lukasz Publication: Physical Review B, Volume 97, Issue 24, id.245106 (PhRvB Homepage) Publication Date: 06/2018 Origin: APS Abstract Copyright: 2018: American Physical Society DOI: 10.1103/PhysRevB.97.245106 Bibliographic Code: 2018PhRvB..97x5106P

### Abstract

We uncover an infinite family of time-reversal symmetric 3 d interacting topological insulators of bosons or spins, in time-periodically driven systems, which we term Floquet topological paramagnets (FTPMs). These FTPM phases exhibit intrinsically dynamical properties that could not occur in thermal equilibrium and are governed by an infinite set of Z2-valued topological invariants, one for each prime number. The topological invariants are physically characterized by surface magnetic domain walls that act as unidirectional quantum channels, transferring quantized packets of information during each driving period. We construct exactly solvable models realizing each of these phases, and discuss the anomalous dynamics of their topologically protected surface states. Unlike previous encountered examples of Floquet SPT phases, these 3 d FTPMs are not captured by group cohomology methods and cannot be obtained from equilibrium classifications simply by treating the discrete time translation as an ordinary symmetry. The simplest such FTPM phase can feature anomalous Z2 (toric code) surface topological order, in which the gauge electric and magnetic excitations are exchanged in each Floquet period, which cannot occur in a pure 2 d system without breaking time reversal symmetry.

 Title: Search for squarks and gluinos in final states with jets and missing transverse momentum using 36 fb-1 of √{s }=13 TeV p p collision data with the ATLAS detector Authors: Aaboud, M.; Aad, G.; Abbott, B.; Abdinov, O.;... Franklin, M.;... Huth, J.;... Morii, M.;... ; and 2869 coauthors Publication: Physical Review D, Volume 97, Issue 11, id.112001 (PhRvD Homepage) Publication Date: 06/2018 Origin: APS Abstract Copyright: 2018: CERN DOI: 10.1103/PhysRevD.97.112001 Bibliographic Code: 2018PhRvD..97k2001A

### Abstract

A search for the supersymmetric partners of quarks and gluons (squarks and gluinos) in final states containing hadronic jets and missing transverse momentum, but no electrons or muons, is presented. The data used in this search were recorded in 2015 and 2016 by the ATLAS experiment in √{s }=13 TeV proton-proton collisions at the Large Hadron Collider, corresponding to an integrated luminosity of 36.1 fb-1. The results are interpreted in the context of various models where squarks and gluinos are pair produced and the neutralino is the lightest supersymmetric particle. An exclusion limit at the 95% confidence level on the mass of the gluino is set at 2.03 TeV for a simplified model incorporating only a gluino and the lightest neutralino, assuming the lightest neutralino is massless. For a simplified model involving the strong production of mass-degenerate first- and second-generation squarks, squark masses below 1.55 TeV are excluded if the lightest neutralino is massless. These limits substantially extend the region of supersymmetric parameter space previously excluded by searches with the ATLAS detector.

 Title: Differential Activity-Driven Instabilities in Biphasic Active Matter Authors: Weber, Christoph A.; Rycroft, Chris H.; Mahadevan, L. Publication: Physical Review Letters, Volume 120, Issue 24, id.248003 (PhRvL Homepage) Publication Date: 06/2018 Origin: APS Abstract Copyright: 2018: American Physical Society DOI: 10.1103/PhysRevLett.120.248003 Bibliographic Code: 2018PhRvL.120x8003W

### Abstract

Active stresses can cause instabilities in contractile gels and living tissues. Here we provide a generic hydrodynamic theory that treats these systems as a mixture of two phases of varying activity and different mechanical properties. We find that differential activity between the phases causes a uniform mixture to undergo a demixing instability. We follow the nonlinear evolution of the instability and characterize a phase diagram of the resulting patterns. Our study complements other instability mechanisms in mixtures driven by differential adhesion, differential diffusion, differential growth, and differential motion.

 Title: Sizing Up the Top Quark's Interaction with the Higgs Authors: Reece, Matthew Publication: Physics, Volume 11, id. 56 Publication Date: 06/2018 Origin: APS Abstract Copyright: 2018: American Physical Society DOI: 10.1103/Physics.11.56 Bibliographic Code: 2018PhyOJ..11...56R

### Abstract

A proton collision experiment at CERN provides a new handle on the Higgs boson's interaction with the heaviest of the quarks.

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