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Articles 31 - 60 of 284
Full-Text Articles in Physics
Demonstration Of Dynamic Thermal Compensation For Parametric Instability Suppression In Advanced Ligo, T. Hardwick, V. J. Hamedan, C. Blair, A. C. Green, D. Vander-Hyde
Demonstration Of Dynamic Thermal Compensation For Parametric Instability Suppression In Advanced Ligo, T. Hardwick, V. J. Hamedan, C. Blair, A. C. Green, D. Vander-Hyde
Faculty Publications
Advanced LIGO and other ground-based interferometric gravitational-wave detectors use high laser power to minimize shot noise and suspended optics to reduce seismic noise coupling. This can result in an opto-mechanical coupling which can become unstable and saturate the interferometer control systems. The severity of these parametric instabilities scales with circulating laser power and first hindered LIGO operations in 2014. Static thermal tuning and active electrostatic damping have previously been used to control parametric instabilities at lower powers but are insufficient as power is increased. Here we report the first demonstration of dynamic thermal compensation to avoid parametric instability in an …
Long-Baseline Neutrino Oscillation Physics Potential Of The Dune Experiment, B. Abi, M. A. Acero, G. Adamov, D. Adams, M. Adinolfi, Z Ahmad, J. Ahmed, T. Alion, S. Alonso Monsalve, C. Alt, J. Anderson, C. Andreopoulos, M. P. Andrews, F. Andringa, A. Ankowski, M. Antonova, S. Antusch, A. Aranda-Fernandez, A. Ariga, L. O. Arnold, Roberto Petti, Et. Al.
Long-Baseline Neutrino Oscillation Physics Potential Of The Dune Experiment, B. Abi, M. A. Acero, G. Adamov, D. Adams, M. Adinolfi, Z Ahmad, J. Ahmed, T. Alion, S. Alonso Monsalve, C. Alt, J. Anderson, C. Andreopoulos, M. P. Andrews, F. Andringa, A. Ankowski, M. Antonova, S. Antusch, A. Aranda-Fernandez, A. Ariga, L. O. Arnold, Roberto Petti, Et. Al.
Faculty Publications
The sensitivity of the Deep Underground Neutrino Experiment (DUNE) to neutrino oscillation is determined, based on a full simulation, reconstruction, and event selection of the far detector and a full simulation and parameterized analysis of the near detector. Detailed uncertainties due to the flux prediction, neutrino interaction model, and detector effects are included. DUNE will resolve the neutrino mass ordering to a precision of 5σ for δCP values, after 2 years of running with the nominal detector design and beam configuration. It has the potential to observe charge-parity violation in the neutrino sector to a precision of 3 …
Modifications To Gravitational Wave Equation From Canonical Quantum Gravity, Andrea Dapor, Klaus Liegener
Modifications To Gravitational Wave Equation From Canonical Quantum Gravity, Andrea Dapor, Klaus Liegener
Faculty Publications
It is expected that the quantum nature of spacetime leaves its imprint in all semiclassical gravitational systems, at least in certain regimes, including gravitational waves. In this paper we investigate such imprints on gravitational waves within a specific framework: space is assumed to be discrete (in the form of a regular cubic lattice), and this discrete geometry is quantised following Dirac's canonical quantisation scheme. The semiclassical behavior is then extracted by promoting the expectation value of the Hamiltonian operator on a semiclassical state to an effective Hamiltonian. Considering a family of semiclassical states representing small tensor perturbations to Minkowski background, …
Expectation Values Of Coherent States For Su(2) Lattice Gauge Theories, Klaus Liegener, Ernst-Albrecht Zwicknagel
Expectation Values Of Coherent States For Su(2) Lattice Gauge Theories, Klaus Liegener, Ernst-Albrecht Zwicknagel
Faculty Publications
This article investigates properties of semiclassical Gauge Field Theory Coherent States for general quantum gauge theories. Useful, e.g., for the canonical formulation of Lattice Gauge Theories these states are labelled by a point in the classical phase space and constructed such that the expectation values of the canonical operators are sharply peaked on said phase space point. For the case of the non-abelian gauge group SU(2), we will explicitly compute the expectation value of general polynomials including the first order quantum corrections. This allows asking more precise questions about the quantum fluctuations of any given semiclassical system.
The Distribution Of Ultra-Diffuse And Ultra-Compact Galaxies In The Frontier Fields, Steven Janssens, Roberto Abraham, Jean Brodie, Duncan Forbes, Aaron Romanowsky
The Distribution Of Ultra-Diffuse And Ultra-Compact Galaxies In The Frontier Fields, Steven Janssens, Roberto Abraham, Jean Brodie, Duncan Forbes, Aaron Romanowsky
Faculty Publications
Large low-surface-brightness galaxies have recently been found to be abundant in nearby galaxy clusters. In this paper, we investigate these ultra-diffuse galaxies (UDGs) in the six Hubble Frontier Fields galaxy clusters: A2744, MACS J0416.1−2403, MACS J0717.5+3745, MACS J1149.5+2223, AS1063, and A370. These are the most massive (1–3 × 1015 M ⊙) and distant (0.308 < z < 0.545) systems in which this class of galaxy has yet been discovered. We estimate that the clusters host of the order of ~200–1400 UDGs inside the virial radius (R 200), consistent with the UDG abundance–halo-mass relation found in the local universe, and suggest that UDGs may be formed in clusters. Within each cluster, however, we find that UDGs are not evenly distributed. Instead their projected spatial distributions are lopsided, and they are deficient in the regions of highest mass density as traced by gravitational lensing. While the deficiency of UDGs in central regions is not surprising, the lopsidedness is puzzling. The UDGs, and their lopsided spatial distributions, may be associated with known substructures late in their infall into the clusters, meaning that we find evidence both for formation of UDGs in clusters and for UDGs falling into clusters. We also investigate the ultra-compact dwarfs (UCDs) residing in the clusters, and find that the spatial distributions of UDGs and UCDs appear anticorrelated. Around 15% of UDGs exhibit either compact nuclei or nearby point sources. Taken together, these observations provide additional evidence for a picture in which at least some UDGs are destroyed in dense cluster environments and leave behind a residue of UCDs.
First Measurement Of Neutrino Oscillation Parameters Using Neutrinos And Antineutrinos By Nova, M. A. Acero, P. Adamson, L. Aliaga, T. Alion, V. Allakhverdian, S. Altakarli, N. Anfimov, A. Antoshkin, A. Aurisano, A. Back, C. Backhouse, M. Baird, N. Balashov, P. Baldi, B. A. Bambah, S. Bashar, K. Bays, S. Bending, R. Bernstein, V. Bhatnagar, Roberto Petti, Et. Al.
First Measurement Of Neutrino Oscillation Parameters Using Neutrinos And Antineutrinos By Nova, M. A. Acero, P. Adamson, L. Aliaga, T. Alion, V. Allakhverdian, S. Altakarli, N. Anfimov, A. Antoshkin, A. Aurisano, A. Back, C. Backhouse, M. Baird, N. Balashov, P. Baldi, B. A. Bambah, S. Bashar, K. Bays, S. Bending, R. Bernstein, V. Bhatnagar, Roberto Petti, Et. Al.
Faculty Publications
The NOvA experiment has seen a 4.4σ signal of ⊽ e appearance in a 2 GeV⊽μ beam at a distance of 810 km. Using 12.33×1020 protons on target delivered to the Fermilab NuMI neutrino beamline, the experiment recorded 27 ⊽μ→⊽e candidates with a background of 10.3 and 102⊽μ→⊽μ candidates. This new antineutrino data are combined with neutrino data to measure the parameters |Δm 2 32 | = 2.48 +0.11 -0.06 x 10 -3 eV2 / c4 and sin2 θ23 in the ranges …
A Precise Determination Of (Anti)Neutrino Fluxes With (Anti)Neutrino-Hydrogen Interactions, H. Duyang, B. Guo, Roberto Petti
A Precise Determination Of (Anti)Neutrino Fluxes With (Anti)Neutrino-Hydrogen Interactions, H. Duyang, B. Guo, Roberto Petti
Faculty Publications
We present a novel method to accurately determine the flux of neutrinos and antineutrinos, one of the dominant systematic uncertainty affecting current and future long-baseline neutrino experiments, as well as precision neutrino scattering experiment. Using exclusive topologies in v(⊽)-hydrogen interactions, vµp→µpπ +, ⊽ µp → µ +pπ, and ⊽µp → µ + n with small hadronic energy, we achieve an overall accuracy on the relative fluxes better than 1% in the energy range covering most of the available flux. Since we cannot rely on simulations nor model …
Hyper Wide Field Imaging Of The Local Group Dwarf Irregular Galaxy Ic 1613: An Extended Component Of Metal-Poor Stars, Ragadeepika Pucha, Jeffrey Carlin, Beth Willman, Jay Strader, David Sand, Keith Bechtol, Jean Brodie, Denija Crnojević, Duncan Forbes, Christopher Garling, Jonathan Hargis, Annika Peter, Aaron Romanowsky
Hyper Wide Field Imaging Of The Local Group Dwarf Irregular Galaxy Ic 1613: An Extended Component Of Metal-Poor Stars, Ragadeepika Pucha, Jeffrey Carlin, Beth Willman, Jay Strader, David Sand, Keith Bechtol, Jean Brodie, Denija Crnojević, Duncan Forbes, Christopher Garling, Jonathan Hargis, Annika Peter, Aaron Romanowsky
Faculty Publications
Stellar halos offer fossil evidence for hierarchical structure formation. Since halo assembly is predicted to be scale-free, stellar halos around low-mass galaxies constrain properties such as star formation in the accreted subhalos and the formation of dwarf galaxies. However, few observational searches for stellar halos in dwarfs exist. Here we present gi photometry of resolved stars in isolated Local Group dwarf irregular galaxy IC 1613 (M sstarf ~ 108 M ⊙). These Subaru/Hyper Suprime-Cam observations are the widest and deepest of IC 1613 to date. We measure surface density profiles of young main-sequence, intermediate to old red giant branch, and …
Spatially Resolved Stellar Kinematics Of The Ultra-Diffuse Galaxy Dragonfly 44. I. Observations, Kinematics, And Cold Dark Matter Halo Fits, Pieter Van Dokkum, Asher Wasserman, Shany Danieli, Roberto Abraham, Jean Brodie, Charlie Conroy, Duncan Forbes, Christopher Martin, Matt Matuszewski, Aaron Romanowsky, Alexa Villaume
Spatially Resolved Stellar Kinematics Of The Ultra-Diffuse Galaxy Dragonfly 44. I. Observations, Kinematics, And Cold Dark Matter Halo Fits, Pieter Van Dokkum, Asher Wasserman, Shany Danieli, Roberto Abraham, Jean Brodie, Charlie Conroy, Duncan Forbes, Christopher Martin, Matt Matuszewski, Aaron Romanowsky, Alexa Villaume
Faculty Publications
We present spatially resolved stellar kinematics of the well-studied ultra-diffuse galaxy (UDG) Dragonfly 44, as determined from 25.3 hr of observations with the Keck Cosmic Web Imager. The luminosity-weighted dispersion within the half-light radius is ${\sigma }_{1/2}={33}_{-3}^{+3}$ km s−1, lower than what we had inferred before from a DEIMOS spectrum in the Hα region. There is no evidence for rotation, with ${V}_{\max }/\langle \sigma \rangle \lt 0.12$ (90% confidence) along the major axis, in possible conflict with models where UDGs are the high-spin tail of the normal dwarf galaxy distribution. The spatially averaged line profile is more peaked than a …
New Constraints On Early-Type Galaxy Assembly From Spectroscopic Metallicities Of Globular Clusters In M87, Alexa Villaume, Aaron Romanowsky, Jean Brodie, Jay Strader
New Constraints On Early-Type Galaxy Assembly From Spectroscopic Metallicities Of Globular Clusters In M87, Alexa Villaume, Aaron Romanowsky, Jean Brodie, Jay Strader
Faculty Publications
The observed characteristics of globular cluster (GC) systems, such as metallicity distributions, are commonly used to place constraints on galaxy formation models. However, obtaining reliable metallicity values is particularly difficult because of our limited means to obtain high quality spectroscopy of extragalactic GCs. Often, "color–metallicity relations" are invoked to convert easier-to-obtain photometric measurements into metallicities, but there is no consensus on what form these relations should take. In this paper we make use of multiple photometric data sets and iron metallicity values derived from applying full-spectrum stellar population synthesis models to deep Keck/LRIS spectra of 177 GCs centrally located around …
Spatially Resolved Stellar Populations And Kinematics With Kcwi: Probing The Assembly History Of The Massive Early-Type Galaxy Ngc 1407, Anna Ferré-Mateu, Duncan Forbes, Richard Mcdermid, Aaron Romanowsky, Jean Brodie
Spatially Resolved Stellar Populations And Kinematics With Kcwi: Probing The Assembly History Of The Massive Early-Type Galaxy Ngc 1407, Anna Ferré-Mateu, Duncan Forbes, Richard Mcdermid, Aaron Romanowsky, Jean Brodie
Faculty Publications
Using the newly commissioned Keck Cosmic Web Imager (KCWI) instrument on the Keck II telescope, we analyze the stellar kinematics and stellar populations of the well-studied massive early-type galaxy (ETG) NGC 1407. We obtained high signal-to-noise integral field spectra for a central and an outer (around one effective radius toward the southeast direction) pointing with integration times of just 600 s and 2400 s, respectively. We confirm the presence of a kinematically distinct core also revealed by VLT/MUSE data of the central regions. While NGC 1407 was previously found to have stellar populations characteristic of massive ETGs (with radially constant …
A Second Galaxy Missing Dark Matter In The Ngc 1052, Pieter Van Dokkum, Shany Danieli, Roberto Abraham, Charlie Conroy, Aaron Romanowsky
A Second Galaxy Missing Dark Matter In The Ngc 1052, Pieter Van Dokkum, Shany Danieli, Roberto Abraham, Charlie Conroy, Aaron Romanowsky
Faculty Publications
The ultra-diffuse galaxy NGC1052-DF2 has a very low velocity dispersion, indicating that it has little or no dark matter. Here we report the discovery of a second galaxy in this class, residing in the same group. NGC1052-DF4 closely resembles NGC1052-DF2 in terms of its size, surface brightness, and morphology; has a similar distance of Dsbf = 19.9 2.8 Mpc; and also has a population of luminous globular clusters extending out to 7 kpc from the center of the galaxy. Accurate radial velocities of the diffuse galaxy light and seven of the globular clusters were obtained with the Low Resolution …
Results From The Cuore Experiment †, Alessio Caminata, Douglas Adams, Chris Alduino, Krystal Alfonso, Frank Avignone Iii, Oscar Azzolini, Giacomo Bari, Fabio Bellini, Giovanni Benato, Andrea Bersani, Matteo Biassoni, Antonio Branca, Chiara Brofferio, Carlo Bucci, Alice Campani, Lucia Canonica, Xi-Guang Cao, Silvia Capelli, Luigi Cappelli, Laura Cardani, Paolo Carniti, Et. Al.
Results From The Cuore Experiment †, Alessio Caminata, Douglas Adams, Chris Alduino, Krystal Alfonso, Frank Avignone Iii, Oscar Azzolini, Giacomo Bari, Fabio Bellini, Giovanni Benato, Andrea Bersani, Matteo Biassoni, Antonio Branca, Chiara Brofferio, Carlo Bucci, Alice Campani, Lucia Canonica, Xi-Guang Cao, Silvia Capelli, Luigi Cappelli, Laura Cardani, Paolo Carniti, Et. Al.
Faculty Publications
The Cryogenic Underground Observatory for Rare Events (CUORE) is the first bolometric experiment searching for neutrinoless double beta decay that has been able to reach the 1-ton scale. The detector consists of an array of 988 TeO2 crystals arranged in a cylindrical compact structure of 19 towers, each of them made of 52 crystals. The construction of the experiment was completed in August 2016 and the data taking started in spring 2017 after a period of commissioning and tests. In this work we present the neutrinoless double beta decay results of CUORE from examining a total TeO2 exposure …
Ground State Phase Diagram Of The One-Dimensional Bose-Hubbard Model From Restricted Boltzmann Machines, Kristopher Mcbrian, Giuseppe Carleo, Ehsan Khatami
Ground State Phase Diagram Of The One-Dimensional Bose-Hubbard Model From Restricted Boltzmann Machines, Kristopher Mcbrian, Giuseppe Carleo, Ehsan Khatami
Faculty Publications
Motivated by recent advances in the representation of ground state wavefunctions of quantum many-body systems using restricted Boltzmann machines as variational ansatz, we utilize an open-source platform for constructing such ansatz called NetKet to explore the extent of applicability of restricted Boltzmann machines to bosonic lattice models. Within NetKet, we design and train these machines for the one-dimensional Bose-Hubbard model through a Monte Carlo sampling of the Fock space. We vary parameters such as the strength of the onsite repulsion, the chemical potential, the system size and the maximum site occupancy and use converged equations of state to identify phase …
Principal Component Analysis Of The Magnetic Transition In The Three-Dimensional Fermi-Hubbard Model, Ehsan Khatami
Principal Component Analysis Of The Magnetic Transition In The Three-Dimensional Fermi-Hubbard Model, Ehsan Khatami
Faculty Publications
Machine learning techniques have been widely used in the study of strongly correlated systems in recent years. Here, we review some applications to classical and quantum many-body systems and present results from an unsupervised machine learning technique, the principal component analysis, employed to identify the finite-temperature phase transition of the three-dimensional Fermi-Hubbard model to the antiferromagnetically ordered state. We find that this linear method can capture the phase transition as well as other more complicated and nonlinear counterparts.
Variations Of Heavy Ion Abundances Relative To Proton Abundances In Large Solar Energetic (E > 10 Mev) Particle Events, J. F. Round, Robert D. Loper, Omar A. Nava, Stephen W. Kahler
Variations Of Heavy Ion Abundances Relative To Proton Abundances In Large Solar Energetic (E > 10 Mev) Particle Events, J. F. Round, Robert D. Loper, Omar A. Nava, Stephen W. Kahler
Faculty Publications
The elemental composition of heavy ions (with atomic number Z > 2) (hi-Z) in large gradual E > 10 MeV nuc-1 SEP events has been extensively studied in the 2-15 MeV nuc-1 range to determine the acceleration processes and transport properties of SEPs. These studies invariably are based on abundances relative to those of a single element such as C or O and often neglect H and He, the elements of primary interest for space weather. The total radiation of an SEP event is determined not only by the H and He properties but also by those of hi-Z ions …
Fluctuating Hydrodynamics Of Reactive Liquid Mixtures, Changho Kim, Andy. Nonaka, John Bell, Alejandro Garcia, Aleksandar Donev
Fluctuating Hydrodynamics Of Reactive Liquid Mixtures, Changho Kim, Andy. Nonaka, John Bell, Alejandro Garcia, Aleksandar Donev
Faculty Publications
Fluctuating hydrodynamics (FHD) provides a framework for modeling microscopic fluctuations in a manner consistent with statistical mechanics and nonequilibrium thermodynamics. This paper presents an FHD formulation for isothermal reactive incompressible liquid mixtures with stochastic chemistry. Fluctuating multispecies mass diffusion is formulated using a Maxwell–Stefan description without assuming a dilute solution, and momentum dynamics is described by a stochastic Navier–Stokes equation for the fluid velocity. We consider a thermodynamically consistent generalization for the law of mass action for non-dilute mixtures and use it in the chemical master equation (CME) to model reactions as a Poisson process. The FHD approach provides remarkable …
Strange And Non-Strange Distributions From The Collider Data, Sergey Alekhin, Johannes Blümlein, Sergey Kulagin, Sven-Olaf Moch, Roberto Petti
Strange And Non-Strange Distributions From The Collider Data, Sergey Alekhin, Johannes Blümlein, Sergey Kulagin, Sven-Olaf Moch, Roberto Petti
Faculty Publications
We check the stability of the ABMP16 fit with respect to modifications of quark PDFs suggested in the recent literature: the strange sea enhancement and a positive non-vanishing d/u ratio at x → 1. These possibilities are examined using test versions of the ABMP16 PDF fit which demonstrate no need of those changes. Furthermore, we localize peculiar features in other analyses which are responsible for a different behaviour of the PDFs obtained. The strange sea enhancement can be explained by a choice of the PDF shapes being not flexible enough and therefore leading to an over-suppressed d-quark distribution. This …
Nuclear Effects In The Deuteron And Global Pdf Fits, S. I. Alekhin, S. A. Kulagin, Roberto Petti
Nuclear Effects In The Deuteron And Global Pdf Fits, S. I. Alekhin, S. A. Kulagin, Roberto Petti
Faculty Publications
We present a detailed study of nuclear corrections in the deuteron (D) from an analysis of data from charged-lepton deep-inelastic scattering (DIS) off proton and D, as well as from dimuon pair production in pp and pD collisions and W± and the Z boson production at pp (p¯p) colliders. In particular, we discuss the determination of the off-shell function describing the modification of parton distributions (PDF) in bound nucleons in the context of global PDF fits. Our results are consistent with the ones obtained earlier from the study of the ratios of DIS structure functions A 2 / F …
Nucleon Pdf Separation With The Collider And Fixed-Target Data, Sergey Alekhin, Johannes Blümlein, Kristin Lohwasser, Lea Michaela Caminada, Katerina Lipka, Ringaile Plačakytė, Sven-Olaf Moch, Roberto Petti
Nucleon Pdf Separation With The Collider And Fixed-Target Data, Sergey Alekhin, Johannes Blümlein, Kristin Lohwasser, Lea Michaela Caminada, Katerina Lipka, Ringaile Plačakytė, Sven-Olaf Moch, Roberto Petti
Faculty Publications
We consider the impact of the recent data obtained by the LHC, Tevatron, and fixed-target experiments on the nucleon quark distributions with a particular focus on disentangling different quark species. An improved determination of the poorly known strange sea distribution is obtained due to including data from the neutrino-induced deep-inelastic scattering experiments NOMAD and CHORUS. The impact of the associated (W + c) production data by CMS and ATLAS on the strange sea determination is also studied and a comparison with earlier results based on the collider data is discussed. Finally, the recent LHC and Tevatron data on …
Nuclear Parton Distributions And The Drell-Yan Reaction, S. A. Kulagin, Roberto Petti
Nuclear Parton Distributions And The Drell-Yan Reaction, S. A. Kulagin, Roberto Petti
Faculty Publications
We discuss the nuclear parton distribution functions on the basis of our recently developed semi-microscopic model, which takes into account a number of nuclear effects including Fermi motion and nuclear binding, nuclear meson-exchange currents and off-shell corrections to bound nucleon distributions as well as nuclear shadowing effect. We also discuss application to the nuclear Drell-Yan process and compare our predictions with data from the E772 and E866 experiments.
Instrument For Precision Long-Term Ss-Decay Rate Measurements, M. J. Ware, Scott D. Bergeson, J. E. Ellsworth, M. Groesbeck, J. E. Hansen, D. Pace, J. Peatross
Instrument For Precision Long-Term Ss-Decay Rate Measurements, M. J. Ware, Scott D. Bergeson, J. E. Ellsworth, M. Groesbeck, J. E. Hansen, D. Pace, J. Peatross
Faculty Publications
We describe an experimental setup for making precision measurements of relative ß-decay rates of 22Na, 36Cl, 54Mn, 60Co, 90Sr, 133Ba, 137Cs, 152Eu, and 154Eu. The radioactive samples are mounted in two automated sample changers that sequentially position the samples with high spatial precision in front of sets of detectors. The set of detectors for one sample changer consists of four Geiger-Müller (GM) tubes and the other set of detectors consists of two NaI scintillators. The statistical uncertainty in the count rate is few times 0.01% per day for the GM …
Linked-Cluster Expansion For The Green's Function Of The Infinite-U Hubbard Model, Ehsan Khatami, Edward Perepelitsky, Marcos Rigol, Sriram B. Shastry
Linked-Cluster Expansion For The Green's Function Of The Infinite-U Hubbard Model, Ehsan Khatami, Edward Perepelitsky, Marcos Rigol, Sriram B. Shastry
Faculty Publications
We implement a highly efficient strong-coupling expansion for the Green's function of the Hubbard model. In the limit of extreme correlations, where the onsite interaction is infinite, the evaluation of diagrams simplifies dramatically enabling us to carry out the expansion to the eighth order in powers of the hopping amplitude. We compute the finite-temperature Green's function analytically in the momentum and Matsubara frequency space as a function of the electron density. Employing Padé approximations, we study the equation of state, Kelvin thermopower, momentum distribution function, quasiparticle fraction, and quasiparticle lifetime of the system at temperatures lower than, or of the …
Fluctuation-Dissipation Theorem In An Isolated System Of Quantum Dipolar Bosons After A Quench, Ehsan Khatami, Guido Pupillo, Mark Srednicki, Marcos Rigol
Fluctuation-Dissipation Theorem In An Isolated System Of Quantum Dipolar Bosons After A Quench, Ehsan Khatami, Guido Pupillo, Mark Srednicki, Marcos Rigol
Faculty Publications
We examine the validity of fluctuation-dissipation relations in isolated quantum systems taken out of equilibrium by a sudden quench. We focus on the dynamics of trapped hard-core bosons in one-dimensional lattices with dipolar interactions whose strength is changed during the quench. We find indications that fluctuation-dissipation relations hold if the system is nonintegrable after the quench, as well as if it is integrable after the quench if the initial state is an equilibrium state of a nonintegrable Hamiltonian. On the other hand, we find indications that they fail if the system is integrable both before and after quenching.
Electronic Spectral Properties Of The Two-Dimensional Infinite-U Hubbard Model, Ehsan Khatami, Daniel Hansen, Edward Perepelitsky, Marcos Rigol, Sriram Shastry
Electronic Spectral Properties Of The Two-Dimensional Infinite-U Hubbard Model, Ehsan Khatami, Daniel Hansen, Edward Perepelitsky, Marcos Rigol, Sriram Shastry
Faculty Publications
A strong-coupling series expansion for the Green's function and the extremely correlated Fermi liquid (ECFL) theory are used to calculate the moments of the electronic spectral functions of the infinite-U Hubbard model. Results from these two complementary methods agree very well at both low densities, where the ECFL solution is the most accurate, and at high to intermediate temperatures, where the series converge. We find that a modified first moment, which underestimates the contributions from the occupied states and is accessible in the series through the time-dependent Green's function, best describes the peak location of the spectral function in the …
A Short Introduction To Numerical Linked-Cluster Expansions, Baoming Tang, Ehsan Khatami, Marcos Rigol
A Short Introduction To Numerical Linked-Cluster Expansions, Baoming Tang, Ehsan Khatami, Marcos Rigol
Faculty Publications
We provide a pedagogical introduction to numerical linked-cluster expansions (NLCEs). We sketch the algorithm for generic Hamiltonians that only connect nearest-neighbor sites in a finite cluster with open boundary conditions. We then compare results for a specific model, the Heisenberg model, in each order of the NLCE with the ones for the finite cluster calculated directly by means of full exact diagonalization. We discuss how to reduce the computational cost of the NLCE calculations by taking into account symmetries and topologies of the linked clusters. Finally, we generalize the algorithm to the thermodynamic limit, and discuss several numerical resummation techniques …
Long-Lived Electron Spins In A Modulation Doped (100) Gaas Quantum Well, John S. Colton, D. Meyer, K Clark, D. Craft, J. Cutler, T. Park, P. White
Long-Lived Electron Spins In A Modulation Doped (100) Gaas Quantum Well, John S. Colton, D. Meyer, K Clark, D. Craft, J. Cutler, T. Park, P. White
Faculty Publications
We have measured T1 spin lifetimes of a 14 nm modulation-doped (100) GaAs quantum well using a time-resolved pump-probe Kerr rotation technique. The quantum well was selected by tuning the wavelength of the probe laser. T1 lifetimes in excess of 1 Us were measured at 1.5 K and 5.5 T, exceeding the typical T2 lifetimes that have been measured in GaAs and II-VI quantum wells by orders of magnitude. We observed effects from nuclear polarization, which were largely removable by simultaneous nuclear magnetic resonance, along with two distinct lifetimes under some conditions that likely result from probing two differently localized …
Effect Of Particle Statistics In Strongly Correlated Two-Dimensional Hubbard Models, Ehsan Khatami, Marcos Rigol
Effect Of Particle Statistics In Strongly Correlated Two-Dimensional Hubbard Models, Ehsan Khatami, Marcos Rigol
Faculty Publications
We study the onset of particle statistics effects as the temperature is lowered in strongly correlated two-dimensional Hubbard models. We utilize numerical linked-cluster expansions and focus on the properties of interacting lattice fermions and two-component hard-core bosons. In the weak-coupling regime, where the ground state of the bosonic system is a superfluid, the thermodynamic properties of the two systems at half filling exhibit very large differences even at high temperatures. In the strong-coupling regime, where the low-temperature behavior is governed by a Mott insulator for either particle statistics, the agreement between the thermodynamic properties of both systems extends to regions …
Student-Teacher Interactions For Bringing Out Student Ideas About Energy, Benedikt W. Harrer, Michael Wittmann, Rachel Scherr
Student-Teacher Interactions For Bringing Out Student Ideas About Energy, Benedikt W. Harrer, Michael Wittmann, Rachel Scherr
Faculty Publications
Modern middle school science curricula use group activities to help students express their thinking and enable them to work together like scientists. We are studying rural 8th grade science classrooms using materials on energy. Even after spending several months with the same curriculum on other physics topics, students' engagement in group activities seems to be restricted to creating lists of words that are associated with energy. Though research suggests that children have rich and potentially valuable ideas about energy, our students don't seem to spontaneously use and express their ideas in the classroom. Only within or after certain interactions with …
Quantum Quenches In Disordered Systems: Approach To Thermal Equilibrium Without A Typical Relaxation Time, Ehsan Khatami, Marcos Rigol, Armando Relaño, Antonio García-García
Quantum Quenches In Disordered Systems: Approach To Thermal Equilibrium Without A Typical Relaxation Time, Ehsan Khatami, Marcos Rigol, Armando Relaño, Antonio García-García
Faculty Publications
We study spectral properties and the dynamics after a quench of one-dimensional spinless fermions with short-range interactions and long-range random hopping. We show that a sufficiently fast decay of the hopping term promotes localization effects at finite temperature, which prevents thermalization even if the classical motion is chaotic. For slower decays, we find that thermalization does occur. However, within this model, the latter regime falls in an unexpected universality class, namely, observables exhibit a power-law (as opposed to an exponential) approach to their thermal expectation values.