Physics Commons^™

All-Sky Search For Continuous Gravitational Waves From Isolated Neutron Stars Using Advanced Ligo O2 Data, B. P. Abbott, R. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present results of an all-sky search for continuous gravitational waves (CWs), which can be produced by fast spinning neutron stars with an asymmetry around their rotation axis, using data from the second observing run of the Advanced LIGO detectors. Three different semicoherent methods are used to search in a gravitational-wave frequency band from 20 to 1922 Hz and a first frequency derivative from -1 × 10^-8 to 2 × 10^-9 Hz/s. None of these searches has found clear evidence for a CW signal, so upper limits on the gravitational-wave strain amplitude are calculated, which for this broad …

Imaging An Isolated Water Molecule Using A Single Electron Wave Packet, Xinyao Liu, Kasra Amini, Tobias Steinle, Anh-Thu Le, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

Observing changes in molecular structure requires atomic-scale Ångstrom and femtosecond spatio-temporal resolution. We use the Fourier transform (FT) variant of laser-induced electron diffraction (LIED), FT-LIED, to directly retrieve the molecular structure of H₂O⁺ with picometer and femtosecond resolution without a priori knowledge of the molecular structure nor the use of retrieval algorithms or ab initio calculations. We identify a symmetrically stretched H₂O⁺ field-dressed structure that is most likely in the ground electronic state. We subsequently study the nuclear response of an isolated water molecule to an external laser field at four different field strengths. …

Multicenter Distorted-Wave Approach For Electron-Impact Ionization Of Molecules, Esam Ali, Don H. Madison

Physics Faculty Research & Creative Works

We have previously used the molecular three-body distorted-wave model to examine electron-impact single ionization of molecules. One of the possible weaknesses of this approach lies in the fact that the continuum electron wave functions do not depend on the orientation of the molecule. Here we introduce a model called the multicenter molecular three-body distorted-wave (MCM3DW) approach, for which the continuum electron wave functions depend on the orientation of the molecule at the time of ionization. The MCM3DW results are compared with experimental data taken from work by Dorn and colleagues [Ren, Phys. Rev. A 91, 032707 (2015)10.1103/PhysRevA.91.032707; Phys. Rev. A …

Impact Of Anharmonicity On The Vibrational Entropy And Specific Heat Of Uo₂, M. S. Bryan, J. W. L. Pang, B. C. Larson, Aleksandr V. Chernatynskiy, D. L. Abernathy, K. Gofryk, M. E. Manley, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

The impact of anharmonicity on the vibrational entropy and heat capacity of UO2 has been investigated from 10 to 1200 K using inelastic neutron-scattering measurements of the phonon density of states (PDOS). Small changes in the PDOS are observed from 10 to 295 K, with more noticeable changes appearing in the 750- and 1200-K data. The specific heat determined from the PDOS measurements is in agreement with macroscopic specific heat measurements, and the overall impact of nondilation anharmonicity on the specific heat has been shown to be less than 2%. An analysis of the phonon measurements shows that the softening …

Narrow-Band Search For Gravitational Waves From Known Pulsars Using The Second Ligo Observing Run, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

Isolated spinning neutron stars, asymmetric with respect to their rotation axis, are expected to be sources of continuous gravitational waves. The most sensitive searches for these sources are based on accurate matched filtering techniques that assume the continuous wave to be phase locked with the pulsar beamed emission. While matched filtering maximizes the search sensitivity, a significant signal-to-noise ratio loss will happen in the case of a mismatch between the assumed and the true signal phase evolution. Narrow-band algorithms allow for a small mismatch in the frequency and spin-down values of the pulsar while coherently integrating the entire dataset. In …

Searches For Gravitational Waves From Known Pulsars At Two Harmonics In 2015-2017 Ligo Data, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present a search for gravitational waves from 221 pulsars with rotation frequencies ≳ 10 Hz. We use advanced LIGO data from its first and second observing runs spanning 2015-2017, which provides the highest-sensitivity gravitational-wave data so far obtained. In this search we target emission from both the l = m = 2 mass quadrupole mode, with a frequency at twice that of the pulsar's rotation, and the l = 2, m = 1 mode, with a frequency at the pulsar rotation frequency. The search finds no evidence for gravitational-wave emission from any pulsar at either frequency. For the l …

Few-Body Dynamics Underlying Postcollision Effects In The Ionization Of H₂ By 75-Kev Proton Impact, M. Dhital, S. Bastola, A. Silvus, Don H. Madison, Michael Schulz

Physics Faculty Research & Creative Works

We have measured fully differential cross sections (FDCS) for ionization in 75-keVp+H2 collisions for ejected electron speeds close to the projectile speed. The data were analyzed in dependence on both the electron emission angle and the projectile scattering angle. Pronounced postcollisional effects between the projectile and the ejected electrons were observed. Significant differences between experiment and theory and between two conceptually very similar theoretical models were found. This shows that in the region of electron-projectile velocity-matching the FDCS is very sensitive to the details of the underlying few-body dynamics.

Quench Dynamics And Orthogonality Catastrophe Of Bose Polarons, Simeon I. Mistakidis, Garyfallia C. Katsimiga, G. M. Koutentakis, Th Busch, P. Schmelcher

Physics Faculty Research & Creative Works

We Monitor The Correlated Quench Induced Dynamical Dressing Of A Spinor Impurity Repulsively Interacting With A Bose-Einstein Condensate. Inspecting The Temporal Evolution Of The Structure Factor, Three Distinct Dynamical Regions Arise Upon Increasing The Interspecies Interaction. These Regions Are Found To Be Related To The Segregated Nature Of The Impurity And To The Ohmic Character Of The Bath. It Is Shown That The Impurity Dynamics Can Be Described By An Effective Potential That Deforms From A Harmonic To A Double-Well One When Crossing The Miscibility-Immiscibility Threshold. In Particular, For Miscible Components The Polaron Formation Is Imprinted On The Spectral Response …

Probing Ferromagnetic Order In Few-Fermion Correlated Spin-Flip Dynamics, G. M. Koutentakis, Simeon I. Mistakidis, P. Schmelcher

Physics Faculty Research & Creative Works

We Unravel The Dynamical Stability Of A Fully Polarized One-Dimensional Ultracold Few-Fermion Spin-1/2 Gas Subjected To Inhomogeneous Driving Of The Itinerant Spins. Despite The Unstable Character Of The Total Spin-Polarization The Existence Of An Interaction Regime Is Demonstrated Where The Spin-Correlations Lead To Almost Maximally Aligned Spins Throughout The Dynamics. The Resulting Ferromagnetic Order Emerges From The Build Up Of Superpositions Of States Of Maximal Total Spin. They Comprise A Decaying Spin-Polarization And A Dynamical Evolution Towards An Almost Completely Unpolarized NOON-Like State. Via Single-Shot Simulations We Demonstrate That Our Theoretical Predictions Can Be Detected In State-Of-The-Art Ultracold Experiments.

Tests Of General Relativity With Gw170817, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

The recent discovery by Advanced LIGO and Advanced Virgo of a gravitational wave signal from a binary neutron star inspiral has enabled tests of general relativity (GR) with this new type of source. This source, for the first time, permits tests of strong-field dynamics of compact binaries in the presence of matter. In this Letter, we place constraints on the dipole radiation and possible deviations from GR in the post-Newtonian coefficients that govern the inspiral regime. Bounds on modified dispersion of gravitational waves are obtained; in combination with information from the observed electromagnetic counterpart we can also constrain effects due …

All-Sky Search For Long-Duration Gravitational-Wave Transients In The Second Advanced Ligo Observing Run, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present the results of a search for long-duration gravitational-wave transients in the data from the Advanced LIGO second observation run; we search for gravitational-wave transients of 2-500 s duration in the 24-2048 Hz frequency band with minimal assumptions about signal properties such as waveform morphologies, polarization, sky location or time of occurrence. Signal families covered by these search algorithms include fallback accretion onto neutron stars, broadband chirps from innermost stable circular orbit waves around rotating black holes, eccentric inspiral-merger-ringdown compact binary coalescence waveforms, and other models. The second observation run totals about 118.3 days of coincident data between November …

Triple Differential Cross Sections For Electron-Impact Ionization Of Methane At Intermediate Energy, Esam Ali, Carlos Granados, Ahmad Sakaamini, Don H. Madison

Physics Faculty Research & Creative Works

We report an experimental and theoretical investigation of electron-impact single ionization of the highest occupied molecular orbital 1t₂ and the next highest occupied molecular orbital 2a₁ states of CH₄ at an incident electron energy of 250 eV. Triple differential cross sections measured in two different laboratories were compared with results calculated within the molecular 3-body distorted wave and generalized Sturmian function theoretical models. For ionization of the 1t₂ state, the binary peak was observed to have a single maximum near the momentum transfer direction that evolved into a double peak for increasing projectile scattering angles, as …

Transverse Localization Of Transmission Eigenchannels, Hasan Yılmaz, Chia Wei Hsu, Alexey Yamilov, Hui Cao

Physics Faculty Research & Creative Works

Transmission eigenchannels are building blocks of coherent wave transport in diffusive media, and selective excitation of individual eigenchannels can lead to diverse transport behaviour. An essential yet poorly understood property is the transverse spatial profile of each eigenchannel, which is relevant for the associated energy density and critical for coupling light into and out of it. Here, we discover that the transmission eigenchannels of a disordered slab possess exponentially localized incident and outgoing profiles, even in the diffusive regime far from Anderson localization. Such transverse localization arises from a combination of reciprocity, local coupling of spatial modes and non-local correlations …

Repulsive Fermi Polarons And Their Induced Interactions In Binary Mixtures Of Ultracold Atoms, Simeon I. Mistakidis, Garyfallia C. Katsimiga, G. M. Koutentakis, P. Schmelcher

Physics Faculty Research & Creative Works

We Explore Repulsive Fermi Polarons In One-Dimensional Harmonically Trapped Few-Body Mixtures Of Ultracold Atoms Using As A Case Example A 6Li-40K Mixture. A Characterization Of These Quasiparticle-Like States, Whose Appearance Is Signaled In The Impurity's Radiofrequency Spectrum, Is Achieved By Extracting Their Lifetime And Residua. Increasing The Number Of 40K Impurities Leads To The Occurrence Of Both Single And Multiple Polarons That Are Entangled With Their Environment. An Interaction-Dependent Broadening Of The Spectral Lines Is Observed Suggesting The Presence Of Induced Interactions. We Propose The Relative Distance Between The Impurities As An Adequate Measure To Detect Induced Interactions Independently Of …

Low-Latency Gravitational-Wave Alerts For Multimessenger Astronomy During The Second Advanced Ligo And Virgo Observing Run, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

Advanced LIGO's second observing run (O2), conducted from 2016 November 30 to 2017 August 25, combined with Advanced Virgo's first observations in 2017 August, witnessed the birth of gravitational-wave multimessenger astronomy. The first ever gravitational-wave detection from the coalescence of two neutron stars, GW170817, and its gamma-ray counterpart, GRB 170817A, led to an electromagnetic follow-up of the event at an unprecedented scale. Several teams from across the world searched for EM/neutrino counterparts to GW170817, paving the way for the discovery of optical, X-ray, and radio counterparts. In this article, we describe the online identification of gravitational-wave transients and the distribution …

Integer Quantum Hall Transition On A Tight-Binding Lattice, Martin Puschmann, Philipp Cain, Michael Schreiber, Thomas Vojta

Physics Faculty Research & Creative Works

Even though the integer quantum Hall transition has been investigated for nearly four decades its critical behavior remains a puzzle. The best theoretical and experimental results for the localization length exponent ν differ significantly from each other, casting doubt on our fundamental understanding. While this discrepancy is often attributed to long-range Coulomb interactions, Gruzberg et al. [Phys. Rev. B 95, 125414 (2017)10.1103/PhysRevB.95.125414] recently suggested that the semiclassical Chalker-Coddington model, widely employed in numerical simulations, is incomplete, questioning the established central theoretical results. To shed light on the controversy, we perform a high-accuracy study of the integer quantum Hall transition for …

Thermomagnetic Properties And Magnetocaloric Effect Of Feconicral-Type High-Entropy Alloys, Suok Min Na, Paul K. Lambert, Hyunsoo Kim, Johnpierre Paglione, Nicholas J. Jones

Physics Faculty Research & Creative Works

In this work, we investigate the effects of substituting Ni/Al for Cr on the thermomagnetic and magnetocaloric properties of FeCoNiCrAl-type high entropy alloys (HEAs). Ni and Al appear to prefer the BCC phase, and increases in the Al composition appear to stabilize the BCC phase. In contrast to Al, Ni content yields an increase in the FCC phase fraction, resulting in a drop off in magnetization. The phase transformation from BCC to FCC was intensified at annealing temperatures of 800 °C and higher due to increased diffusion rates and the resulting spinodal decomposition. A magnetic phase transition around 150 K …

Reply To "Comment On 'Coherent-State Path Integrals In The Continuum'", G. Kordas, Simeon I. Mistakidis, A. I. Karanikas

Physics Faculty Research & Creative Works

In This Reply We Briefly Clarify The Main Points Of Our Method To Construct Coherent-State Path Integrals In The Continuum And We Reply To The Critique Raised By In The Preceding Comment By Kochetov [Phys. Rev. A 99, 026101 (2019)10.1103/PhysRevA.99.026101]. By Using Definite Examples, We Prove That Our Approach Is Capable Of Resolving The Inconsistencies Accompanying The Standard Coherent-State Path-Integral Representation Of Interacting Systems.

Low Energy Electron And Positron Impact Differential Cross Sections For The Ionization Of Water Molecules In The Coplanar And Perpendicular Kinematics, P. Singh, G. Purohit, C. Champion, D. Sebilleau, Don H. Madison

Physics Faculty Research & Creative Works

We report here triply differential cross sections (TDCSs) for 81 eV electron and positron-impact ionization of the combined (1b₁ + 3a1 ) orbitals of the water molecule by using the second-order distorted wave Born approximation (DWBA2) for ejection electron and positron energies of 5 eV and 10 eV and different momentum transfer conditions. The electron-impact TDCS will be compared with the experimental data measured by Ren et al. [Phys. Rev. A 95, 022701 (2017)] and with the molecular 3-body distorted wave (M3DW) approximation results in the scattering plane as well as the perpendicular plane. The DWBA2 results are …

Constraining The P-Mode-G-Mode Tidal Instability With Gw170817, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We analyze the impact of a proposed tidal instability coupling p modes and g modes within neutron stars on GW170817. This nonresonant instability transfers energy from the orbit of the binary to internal modes of the stars, accelerating the gravitational-wave driven inspiral. We model the impact of this instability on the phasing of the gravitational wave signal using three parameters per star: An overall amplitude, a saturation frequency, and a spectral index. Incorporating these additional parameters, we compute the Bayes factor (ln B^pg_!pg) comparing our p-g model to a standard one. We find that the observed signal …

Fractional Brownian Motion In A Finite Interval: Correlations Effect Depletion Or Accretion Zones Of Particles Near Boundaries, T. Guggenberger, G. Pagnini, Thomas Vojta, R. Metzler

Physics Faculty Research & Creative Works

Fractional Brownian motion (FBM) is a Gaussian stochastic process with stationary, long-time correlated increments and is frequently used to model anomalous diffusion processes. We study numerically FBM confined to a finite interval with reflecting boundary conditions. The probability density function of this reflected FBM at long times converges to a stationary distribution showing distinct deviations from the fully flat distribution of amplitude 1/L in an interval of length L found for reflected normal Brownian motion. While for superdiffusion, corresponding to a mean squared displacement (MSD) ⟨X²(t)⟩ ≃ t^α with 1 < α < 2, the probability density function is lowered in the centre of the interval and rises towards the boundaries, for subdiffusion (0 < α < 1) this behaviour is reversed and the particle density is depleted close to the boundaries. The MSD in these cases at long times converges to a stationary value, which is, remarkably, monotonically increasing with the anomalous diffusion exponent α. Our a priori surprising results may have interesting …

Infinite-Randomness Fixed Point Of The Quantum Superconductor-Metal Transitions In Amorphous Thin Films, Nicholas A. Lewellyn, Ilana M. Percher, J. J. Nelson, Javier Garcia-Barriocanal, Irina Volotsenko, Aviad Frydman, Thomas Vojta, Allen M. Goldman

Physics Faculty Research & Creative Works

The magnetic-field-tuned quantum superconductor-insulator transitions of disordered amorphous indium oxide films are a paradigm in the study of quantum phase transitions and exhibit power-law scaling behavior. For superconducting indium oxide films with low disorder, such as the ones reported on here, the high-field state appears to be a quantum-corrected metal. Resistance data across the superconductor-metal transition in these films are shown here to obey an activated scaling form appropriate to a quantum phase transition controlled by an infinite-randomness fixed point in the universality class of the random transverse-field Ising model. Collapse of the field-dependent resistance vs temperature data is obtained …

Phase-Separation Dynamics Induced By An Interaction Quench Of A Correlated Fermi-Fermi Mixture In A Double Well, J. Erdmann, Simeon I. Mistakidis, P. Schmelcher

Physics Faculty Research & Creative Works

We Explore The Interspecies Interaction Quench Dynamics Of Ultracold Spin-Polarized Few-Body Mass-Balanced Fermi-Fermi Mixtures Confined In A Double Well With An Emphasis On The Beyond Hartree-Fock Correlation Effects. It Is Shown That The Ground State Of Particle-Imbalanced Mixtures Exhibits A Symmetry Breaking Of The Single-Particle Density For Strong Interactions In The Hartree-Fock Limit, Which Is Altered Within The Many-Body Approach. Quenching The Interspecies Repulsion Towards The Strongly Interacting Regime, The Two Species Phase Separate Within The Hartree-Fock Approximation While Remaining Miscible In The Many-Body Treatment. Despite Their Miscible Character On The One-Body Level, The Two Species Are Found To Be …

Resonance Strengths For Kll Dielectronic Recombination Of Highly Charged Mercury Ions And Improved Empirical Z -Scaling Law, Zoltan Harman, Chintan Shah, Antonio J. Gonzalez Martinez, Ulrich D. Jentschura, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

Theoretical and experimental resonance strengths for KLL dielectronic recombination (DR) into He-, Li-, Be-, and B-like mercury ions are presented, based on state-resolved DR x-ray spectra recorded at the Heidelberg electron-beam ion trap. The DR resonance strengths are experimentally extracted by normalizing them to simultaneously recorded radiative recombination signals. The results are compared to state-of-the-art atomic calculations that include relativistic electron correlation and configuration mixing effects. Combining the present data with other existing ones, we derive an improved semiempirical Z-scaling law for DR resonance strengths as a function of the atomic number, taking into account higher-order relativistic corrections, which are …

Applications Of Machine Learning In Nuclear Imaging And Radiation Detection, Shaikat Mahmood Galib

Doctoral Dissertations

"The main focus of this work is to use machine learning and data mining techniques to address some challenging problems that arise from nuclear data. Specifically, two problem areas are discussed: nuclear imaging and radiation detection. The techniques to approach these problems are primarily based on a variant of Artificial Neural Network (ANN) called Convolutional Neural Network (CNN), which is one of the most popular forms of 'deep learning' technique.

The first problem is about interpreting and analyzing 3D medical radiation images automatically. A method is developed to identify and quantify deformable image registration (DIR) errors from lung CT scans …

Properties Of The Binary Neutron Star Merger Gw170817, B. P. Abbott, R. Abbott, T. D. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

On August 17, 2017, the Advanced LIGO and Advanced Virgo gravitational-wave detectors observed a low-mass compact binary inspiral. The initial sky localization of the source of the gravitational-wave signal, GW170817, allowed electromagnetic observatories to identify NGC 4993 as the host galaxy. In this work, we improve initial estimates of the binary's properties, including component masses, spins, and tidal parameters, using the known source location, improved modeling, and recalibrated Virgo data. We extend the range of gravitational-wave frequencies considered down to 23 Hz, compared to 30 Hz in the initial analysis. We also compare results inferred using several signal models, which …

Ferrite Characterization Techniques & Particle Simulations For Semiconductor Devices, Nicholas Erickson

Doctoral Dissertations

"This dissertation is divided into three papers, covering two major topics. The first topic, techniques for ferrite characterization, is discussed over the course of two papers. The second topic, particle simulations for semiconductor devices, is discussed in the last paper. In the first paper, the method for extracting permeability from ferrite materials is discussed for the Keysight 16454A permeability extraction fixture, where the ferrite material to be characterized is assumed to be homogeneous. Then the method is updated to account for layered materials. The updated method is verified through full-wave simulations. In the second paper, a planar printed circuit board …

Development Of A Switchable Radioisotope Generator, Kyle Mitchell Paaren

Doctoral Dissertations

The Switchable Radioisotope Generator utilizes alpha-induced reactions to produce a combination of photons, neutrons, and protons with varying fluxes dependent on target materials and source geometry. The activity/strength of the secondary radiation is further controlled by manipulating the number of alpha particles that can interact with the target material(s). Analytical equations were solved to confirm secondary radiation production from target materials using average cross sections from TENDL data. TENDL and JENDL data was confirmed by analytically solving for the total alpha-induced cross sections. This information was used to produce the provisional and utility Patent No: US20190013109A1. TENDL data was then …

Characterization Of A Green Electric Solid Propellant For Electric Propulsion, Matthew Scott Glascock

Doctoral Dissertations

"Electric solid propellants are advanced solid chemical rocket propellants that can be controlled (ignited, throttled and extinguished) through the application and removal of an electric current. These propellants are also being considered for use in ablative pulsed plasma thruster and multimode systems. In this work, the behavior and performance of a novel green electric solid propellant operating in an electrothermal ablation-fed pulsed plasma thruster was investigated. Using an inverted pendulum micro-Newton thrust stand, the impulse bit and specific impulse of the device using the electric solid propellant were measured for short-duration and long-duration runs to end-of-life, at energy levels of …

Modelling And Evaluation Of Electrical Resonance Eddy Current For Submillimeter Defect Detection, Yew San Hor, Vinod K. Sivaraja, Yu Zhong, Bui V. Phuong, Christopher Lane

Physics Faculty Research & Creative Works

Eddy current (EC) inspection is used extensively in non-destructive testing (NDT) to detect surface-breaking defects of engineering components. However, the sensitivity of conventional eddy current inspection has plateaued in recent years. The ability to detect submillimetre defects before it becomes critical would allow engineering components to remain in-service safely for longer. Typically, it is required that higher frequency EC is employed to achieve a suitable sensitivity for detection of such submillimetre defects. However, that would lead to significant electromagnetic noise affecting the sensitivity of the inspection. To overcome this issue, the electrical-resonance based eddy current method has been proposed, where …