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Physics Faculty Research & Creative Works

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Articles 511 - 540 of 1959

Full-Text Articles in Physical Sciences and Mathematics

All-Sky Search For Short Gravitational-Wave Bursts In The First Advanced Ligo Run, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Feb 2017

All-Sky Search For Short Gravitational-Wave Bursts In The First Advanced Ligo Run, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present the results from an all-sky search for short-duration gravitational waves in the data of the first run of the Advanced LIGO detectors between September 2015 and January 2016. The search algorithms use minimal assumptions on the signal morphology, so they are sensitive to a wide range of sources emitting gravitational waves. The analyses target transient signals with duration ranging from milliseconds to seconds over the frequency band of 32 to 4096 Hz. The first observed gravitational-wave event, GW150914, has been detected with high confidence in this search; the other known gravitational-wave event, GW151226, falls below the search's sensitivity. …

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Long-Range Interactions Of Hydrogen Atoms In Excited States. I. 2s-1s Interactions And Dirac-Δ Perturbations, Chandra Mani Adhikari, Vincent Debierre, Arthur N. Matveev, Nikolai N. Kolachevsky, Ulrich D. Jentschura Feb 2017

Long-Range Interactions Of Hydrogen Atoms In Excited States. I. 2s-1s Interactions And Dirac-Δ Perturbations, Chandra Mani Adhikari, Vincent Debierre, Arthur N. Matveev, Nikolai N. Kolachevsky, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

The theory of the long-range interaction of metastable excited atomic states with ground-state atoms is analyzed. We show that the long-range interaction is essentially modified when quasidegenerate states are available for virtual transitions. A discrepancy in the literature regarding the van der Waals coefficient C6 (2S ;1 S ) describing the interaction of metastable atomic hydrogen ( 2 S state) with a ground-state hydrogen atom is resolved. In the the van der Waals range a0 ≪ R ≪ a0 / α , where a0 = ℏ / α m c is the Bohr radius and α …

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Long-Range Interactions Of Hydrogen Atoms In Excited States. Ii. Hyperfine-Resolved 2s-2s Systems, Ulrich D. Jentschura, Vincent Debierre, Chandra Mani Adhikari, Arthur N. Matveev, Nikolai N. Kolachevsky Feb 2017

Long-Range Interactions Of Hydrogen Atoms In Excited States. Ii. Hyperfine-Resolved 2s-2s Systems, Ulrich D. Jentschura, Vincent Debierre, Chandra Mani Adhikari, Arthur N. Matveev, Nikolai N. Kolachevsky

Physics Faculty Research & Creative Works

The interaction of two excited hydrogen atoms in metastable states constitutes a theoretically interesting problem because of the quasidegenerate 2P1/2 levels that are removed from the 2S states only by the Lamb shift. The total Hamiltonian of the system is composed of the van der Waals Hamiltonian, the Lamb shift, and the hyperfine effects. The van der Waals shift becomes commensurate with the 2S-2P3/2 fine-structure splitting only for close approach (R < 100a0, where a0 is the Bohr radius) and one may thus restrict the discussion to the levels with n = 2 and J = 1/2 …

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Monte Carlo Simulations Of The Disordered Three-Color Quantum Ashkin-Teller Chain, Ahmed K. Ibrahim, Thomas Vojta Feb 2017

Monte Carlo Simulations Of The Disordered Three-Color Quantum Ashkin-Teller Chain, Ahmed K. Ibrahim, Thomas Vojta

Physics Faculty Research & Creative Works

We investigate the zero-temperature quantum phase transitions of the disordered three-color quantum Ashkin-Teller spin chain by means of large-scale Monte Carlo simulations. We find that the first-order phase transitions of the clean system are rounded by the quenched disorder. For weak intercolor coupling, the resulting emergent quantum critical point between the paramagnetic phase and the magnetically ordered Baxter phase is of infinite-randomness type and belongs to the universality class of the random transverse-field Ising model, as predicted by recent strong-disorder renormalization group calculations. We also find evidence for unconventional critical behavior in the case of strong intercolor coupling, even though …

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Ionization Study Of Isomeric Molecules In Strong-Field Laser Pulses, Stefan Zigo, Anh-Thu Le, Pratap Timilsina, Carlos A. Trallero-Herrero Feb 2017

Ionization Study Of Isomeric Molecules In Strong-Field Laser Pulses, Stefan Zigo, Anh-Thu Le, Pratap Timilsina, Carlos A. Trallero-Herrero

Physics Faculty Research & Creative Works

Through the use of the technique of time-of-flight mass spectroscopy, we obtain strong-field ionization yields for randomly oriented 1,2-dichloroethylene (1,2-DCE) (C₂H₂Cl₂) and 2-butene (C₄H₈). We are interested in studying the effect of conformal structure in strong-field ionization and, in particular, the role of molecular polarity. That is, we can perform strong-field ionization studies in polar vs non-polar molecules that have the same chemical composition. We report our findings through the ionization yields and the ratio (trans/cis) of each stereoisomer pair as a function of intensity.

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Mode Coupling Of Interaction Quenched Ultracold Few-Boson Ensembles In Periodically Driven Lattices, Simeon I. Mistakidis, P. Schmelcher Jan 2017

Mode Coupling Of Interaction Quenched Ultracold Few-Boson Ensembles In Periodically Driven Lattices, Simeon I. Mistakidis, P. Schmelcher

Physics Faculty Research & Creative Works

The Out-Of-Equilibrium Dynamics Of Interaction Quenched Finite Ultracold Bosonic Ensembles In Periodically Driven One-Dimensional Optical Lattices Is Investigated. It Is Shown That Periodic Driving Enforces The Bosons In The Outer Wells Of The Finite Lattice To Exhibit Out-Of-Phase Dipolelike Modes, While In The Central Well The Atomic Cloud Experiences A Local Breathing Mode. The Dynamical Behavior Is Investigated With Varying Driving Frequencies, Revealing Resonantlike Behavior Of The Intrawell Dynamics. An Interaction Quench In The Periodically Driven Lattice Gives Rise To Admixtures Of Different Excitations In The Outer Wells, Enhanced Breathing In The Center, And Amplification Of The Tunneling Dynamics. We …

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Dark-Bright Soliton Interactions Beyond The Integrable Limit, Garyfallia C. Katsimiga, J. Stockhofe, P. G. Kevrekidis, P. Schmelcher Jan 2017

Dark-Bright Soliton Interactions Beyond The Integrable Limit, Garyfallia C. Katsimiga, J. Stockhofe, P. G. Kevrekidis, P. Schmelcher

Physics Faculty Research & Creative Works

In this work we present a systematic theoretical analysis regarding dark-bright solitons and their interactions, motivated by recent advances in atomic two-component repulsively interacting Bose-Einstein condensates. In particular, we study analytically via a two-soliton ansatz adopted within a variational formulation the interaction between two dark-bright solitons in a homogeneous environment beyond the integrable regime, by considering general inter- and intra-atomic interaction coefficients. We retrieve the possibility of a fixed point in the case where the bright solitons are out of phase. As the intercomponent interaction is increased, we also identify an exponential instability of the two-soliton state, associated with a …

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Quench-Induced Resonant Tunneling Mechanisms Of Bosons In An Optical Lattice With Harmonic Confinement, G. M. Koutentakis, Simeon I. Mistakidis, P. Schmelcher Jan 2017

Quench-Induced Resonant Tunneling Mechanisms Of Bosons In An Optical Lattice With Harmonic Confinement, G. M. Koutentakis, Simeon I. Mistakidis, P. Schmelcher

Physics Faculty Research & Creative Works

The Nonequilibrium Dynamics Of Small Boson Ensembles In A One-Dimensional Optical Lattice Is Explored Upon A Sudden Quench Of An Additional Harmonic Trap From Strong To Weak Confinement. We Find That The Competition Between The Initial Localization And The Repulsive Interaction Leads To A Resonant Response Of The System For Intermediate Quench Amplitudes, Corresponding To Avoided Crossings In The Many-Body Eigenspectrum With Varying Final Trap Frequency. In Particular, We Show That These Avoided Crossings Can Be Utilized To Prepare The System In A Desired State. The Dynamical Response Is Shown To Depend On Both The Interaction Strength As Well As …

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Textured Nise₂ Film: Bifunctional Electrocatalyst For Full Water Splitting At Remarkably Low Overpotential With High Energy Efficiency, Abdurazag T. Swesi, Jahangir Masud, Wipula P. R. Liyanage, Siddesh Umapathi, Eric W. Bohannan, Julia E. Medvedeva, Manashi Nath Jan 2017

Textured Nise₂ Film: Bifunctional Electrocatalyst For Full Water Splitting At Remarkably Low Overpotential With High Energy Efficiency, Abdurazag T. Swesi, Jahangir Masud, Wipula P. R. Liyanage, Siddesh Umapathi, Eric W. Bohannan, Julia E. Medvedeva, Manashi Nath

Physics Faculty Research & Creative Works

Herein we have shown that electrodeposited NiSe2 can be used as a bifunctional electrocatalyst under alkaline conditions to split water at very low potential by catalyzing both oxygen evolution and hydrogen evolution reactions at anode and cathode, respectively, achieving a very high electrolysis energy efficiency exceeding 80% at considerably high current densities (100 mA cm-2). The OER catalytic activity as well as electrolysis energy efficiency surpasses any previously reported OER electrocatalyst in alkaline medium and energy efficiency of an electrolyzer using state-of-the-art Pt and RuO2 as the HER and OER catalyst, respectively. Through detailed electrochemical and …

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The Clustering Of Galaxies In The Completed Sdss-Iii Baryon Oscillation Spectroscopic Survey: Observational Systematics And Baryon Acoustic Oscillations In The Correlation Function, Ashley J. Ross, Florian Beutler, Shun Saito, For Full List Of Authors, See Publisher's Website. Jan 2017

The Clustering Of Galaxies In The Completed Sdss-Iii Baryon Oscillation Spectroscopic Survey: Observational Systematics And Baryon Acoustic Oscillations In The Correlation Function, Ashley J. Ross, Florian Beutler, Shun Saito, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present baryon acoustic oscillation (BAO) scale measurements determined from the clustering of 1.2 million massive galaxies with redshifts 0.2 < z < 0.75 distributed over 9300 deg2, as quantified by their redshift-space correlation function. In order to facilitate these measurements, we define, describe, and motivate the selection function for galaxies in the final data release (DR12) of the SDSS III Baryon Oscillation Spectroscopic Survey (BOSS). This includes the observational footprint, masks for image quality and Galactic extinction, and weights to account for density relationships intrinsic to the imaging and spectroscopic portions of the survey. We simulate the observed systematic trends in mock galaxy samples and …

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Enhancing Light Transmission Through A Disordered Waveguide With Inhomogeneous Scattering And Loss, Raktim Sarma, Alexey Yamilov, Hui Cao Jan 2017

Enhancing Light Transmission Through A Disordered Waveguide With Inhomogeneous Scattering And Loss, Raktim Sarma, Alexey Yamilov, Hui Cao

Physics Faculty Research & Creative Works

We enhanced the total transmission of light through a disordered waveguide with spatially inhomogeneous scattering and loss by shaping the incident wavefront of a laser beam. Using an on-chip tapered lead, we were able to access all input modes in the waveguide with a spatial light modulator. The adaptive wavefront shaping resulted in selective coupling of input light to high transmission channels, which bypassed the regions of higher scattering and loss in the waveguide. Spatial inhomogeneity in scattering and loss leads to the modification of the spatial structures of transmission eigenchannels, allowing wavefront shaping to redirect the energy flux to …

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Rotational Symmetry Breaking In A Trigonal Superconductor Nb-Doped Bi₂Se₃, T. Asaba, B. J. Lawson, C. Tinsman, L. Chen, P. Corbae, G. Li, Y. Qiu, Yew San Hor, L. Fu, L. Li Jan 2017

Rotational Symmetry Breaking In A Trigonal Superconductor Nb-Doped Bi₂Se₃, T. Asaba, B. J. Lawson, C. Tinsman, L. Chen, P. Corbae, G. Li, Y. Qiu, Yew San Hor, L. Fu, L. Li

Physics Faculty Research & Creative Works

The search for unconventional superconductivity has been focused on materials with strong spin-orbit coupling and unique crystal lattices. Doped bismuth selenide (Bi2Se3) is a strong candidate, given the topological insulator nature of the parent compound and its triangular lattice. The coupling between the physical properties in the superconducting state and its underlying crystal symmetry is a crucial test for unconventional superconductivity. In this paper, we report direct evidence that the superconducting magnetic response couples strongly to the underlying trigonal crystal symmetry in the recently discovered superconductor with trigonal crystal structure, niobium (Nb)-doped Bi2Se3 …

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De Haas-Van Alphen Study Of Role Of 4f Electrons In Antiferromagnetic Cezn₁₁ As Compared To Its Nonmagnetic Analog Lazn₁₁, S. F. Blake, Halyna Hodovanets, A. Mccollam, S. L. Bud'ko, P. C. Canfield, A. I. Coldea Dec 2016

De Haas-Van Alphen Study Of Role Of 4f Electrons In Antiferromagnetic Cezn₁₁ As Compared To Its Nonmagnetic Analog Lazn₁₁, S. F. Blake, Halyna Hodovanets, A. Mccollam, S. L. Bud'ko, P. C. Canfield, A. I. Coldea

Physics Faculty Research & Creative Works

We present a de Haas-van Alphen study of the Fermi surface of the low-temperature antiferromagnet CeZn11 and its nonmagnetic analog LaZn11, measured by torque magnetometry up to fields of 33T and at temperatures down to 320mK. Both systems possess similar de Haas-van Alphen frequencies, with three clear sets of features -- ranging from 50T to 4kT -- corresponding to three bands of a complex Fermi surface, with an expected fourth band also seen weakly in CeZn11. The effective masses of the charge carriers are very light ( < 1me) in LaZn11 but a factor …

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Prospects For Observing And Localizing Gravitational-Wave Transients With Advanced Ligo And Advanced Virgo, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Dec 2016

Prospects For Observing And Localizing Gravitational-Wave Transients With Advanced Ligo And Advanced Virgo, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present a possible observing scenario for the Advanced LIGO and Advanced Virgo gravitational-wave detectors over the next decade, with the intention of providing information to the astronomy community to facilitate planning for multi-messenger astronomy with gravitational waves. We determine the expected sensitivity of the network to transient gravitational-wave signals, and study the capability of the network to determine the sky location of the source. We report our findings for gravitational-wave transients, with particular focus on gravitational-wave signals from the inspiral of binary neutron-star systems, which are considered the most promising for multi-messenger astronomy. The ability to localize the sources …

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High Order Harmonic Generation From Sf₆: Deconvolution Of Macroscopic Effects, B. P. Wilson, K. D. Fulfer, S. Mondal, X. Ren, J. Tross, E. D. Poliakoff, J. Jose, Anh-Thu Le, R. R. Lucchese, Carlos A. Trallero-Herrero Dec 2016

High Order Harmonic Generation From Sf₆: Deconvolution Of Macroscopic Effects, B. P. Wilson, K. D. Fulfer, S. Mondal, X. Ren, J. Tross, E. D. Poliakoff, J. Jose, Anh-Thu Le, R. R. Lucchese, Carlos A. Trallero-Herrero

Physics Faculty Research & Creative Works

We measure high order harmonics from the molecule SF₆ over a large range of phase matching conditions and observe several features in the harmonics that are largely independent of such macroscopic conditions. The experimental data are then compared to the quantitative rescattering theory for the generation of harmonics from three orbitals. With this comparison, we are able to assign spectroscopic features in the harmonics to contributions from 1t1g (HOMO) and 5t1u (HOMO-1) orbitals.

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First Targeted Search For Gravitational-Wave Bursts From Core-Collapse Supernovae In Data Of First-Generation Laser Interferometer Detectors, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Nov 2016

First Targeted Search For Gravitational-Wave Bursts From Core-Collapse Supernovae In Data Of First-Generation Laser Interferometer Detectors, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present results from a search for gravitational-wave bursts coincident with two core-collapse supernovae observed optically in 2007 and 2011. We employ data from the Laser Interferometer Gravitational-wave Observatory (LIGO), the Virgo gravitational-wave observatory, and the GEO 600 gravitational-wave observatory. The targeted core-collapse supernovae were selected on the basis of (1) proximity (within approximately 15 Mpc), (2) tightness of observational constraints on the time of core collapse that defines the gravitational-wave search window, and (3) coincident operation of at least two interferometers at the time of core collapse. We find no plausible gravitational-wave candidates. We present the probability of detecting …

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Results Of The Deepest All-Sky Survey For Continuous Gravitational Waves On Ligo S6 Data Running On The Einstein@Home Volunteer Distributed Computing Project, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Nov 2016

Results Of The Deepest All-Sky Survey For Continuous Gravitational Waves On Ligo S6 Data Running On The Einstein@Home Volunteer Distributed Computing Project, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We report results of a deep all-sky search for periodic gravitational waves from isolated neutron stars in data from the S6 LIGO science run. The search was possible thanks to the computing power provided by the volunteers of the Einstein@Home distributed computing project. We find no significant signal candidate and set the most stringent upper limits to date on the amplitude of gravitational wave signals from the target population. At the frequency of best strain sensitivity, between 170.5 and 171 Hz we set a 90% confidence upper limit of 5.5 x 10-25, while at the high end of …

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The Rate Of Binary Black Hole Mergers Inferred From Advanced Ligo Observations Surrounding Gw150914, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Nov 2016

The Rate Of Binary Black Hole Mergers Inferred From Advanced Ligo Observations Surrounding Gw150914, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

A transient gravitational-wave signal, GW150914, was identified in the twin Advanced LIGO detectors on 2015 September 2015 at 09:50:45 UTC. To assess the implications of this discovery, the detectors remained in operation with unchanged configurations over a period of 39 days around the time of the signal. At the detection statistic threshold corresponding to that observed for GW150914, our search of the 16 days of simultaneous two-detector observational data is estimated to have a false-alarm rate (FAR) of < 4.9 x 10-6 yr-1, yielding a p-value for GW150914 of < 2 x 10-7. Parameter estimation follow-up on this trigger identifies its source …

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Binary Black Hole Mergers In The First Advanced Ligo Observing Run, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Oct 2016

Binary Black Hole Mergers In The First Advanced Ligo Observing Run, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

The first observational run of the Advanced LIGO detectors, from September 12, 2015 to January 19, 2016, saw the first detections of gravitational waves from binary black hole mergers. In this paper, we present full results from a search for binary black hole merger signals with total masses up to 100M⊙ and detailed implications from our observations of these systems. Our search, based on general-relativistic models of gravitational-wave signals from binary black hole systems, unambiguously identified two signals, GW150914 and GW151226, with a significance of greater than 5σ over the observing period. It also identified a third possible signal, …

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Improved Analysis Of Gw150914 Using A Fully Spin-Precessing Waveform Model, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Oct 2016

Improved Analysis Of Gw150914 Using A Fully Spin-Precessing Waveform Model, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

This paper presents updated estimates of source parameters for GW150914, a binary black-hole coalescence event detected by the Laser Interferometer Gravitational-wave Observatory (LIGO) in 2015 [Abbott et al. Phys. Rev. Lett. 116, 061102 (2016).]. Abbott et al. [Phys. Rev. Lett. 116, 241102 (2016).] presented parameter estimation of the source using a 13-dimensional, phenomenological precessing-spin model (precessing IMRPhenom) and an 11-dimensional nonprecessing effective-one body (EOB) model calibrated to numerical-relativity simulations, which forces spin alignment (nonprecessing EOBNR). Here, we present new results that include a 15-dimensional precessing-spin waveform model (precessing EOBNR) developed within the EOB formalism. We find good agreement …

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Quantum Critical Behavior Of The Superfluid-Mott Glass Transition, Thomas Vojta, Jack Crewse, Martin Puschmann, Daniel Arovas, Yury Kiselev Oct 2016

Quantum Critical Behavior Of The Superfluid-Mott Glass Transition, Thomas Vojta, Jack Crewse, Martin Puschmann, Daniel Arovas, Yury Kiselev

Physics Faculty Research & Creative Works

We investigate the zero-temperature superfluid to insulator transitions in a diluted two-dimensional quantum rotor model with particle-hole symmetry. We map the Hamiltonian onto a classical (2+1)-dimensional XY model with columnar disorder which we analyze by means of large-scale Monte Carlo simulations. For dilutions below the lattice percolation threshold, the system undergoes a generic superfluid-Mott glass transition. In contrast to other quantum phase transitions in disordered systems, its critical behavior is of conventional power-law type with universal (dilution-independent) critical exponents z=1.52(3), ν =1.16(5), ß/ν =0.48(2), γ/ν=2.52(4), and η = -0.52(4). These values agree with and improve upon earlier Monte Carlo results …

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Magic Wavelength For The Hydrogen 1s-2s Transition: Contribution Of The Continuum And The Reduced-Mass Correction, Chandra M. Adhikari, A. Kawasaki, Ulrich D. Jentschura Sep 2016

Magic Wavelength For The Hydrogen 1s-2s Transition: Contribution Of The Continuum And The Reduced-Mass Correction, Chandra M. Adhikari, A. Kawasaki, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

Recently, we studied the magic wavelength for the atomic hydrogen 1S-2S transition [A. Kawasaki, Phys. Rev. A 92, 042507 (2015)PLRAAN1050-294710.1103/PhysRevA.92.042507]. An explicit summation over virtual atomic states of the discrete part of the hydrogen spectrum was performed to evaluate the atomic polarizability. In this paper, we supplement the contribution of the continuum part of the spectrum and add the reduced-mass correction. The magic wavelength, at which the lowest-order ac Stark shifts of the 1S and 2S states are equal, is found to be 514.6 nm. The ac Stark shift at the magic wavelength is -221.6Hz/(kW/cm2), and the slope …

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Directly Comparing Gw150914 With Numerical Solutions Of Einstein's Equations For Binary Black Hole Coalescence, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Sep 2016

Directly Comparing Gw150914 With Numerical Solutions Of Einstein's Equations For Binary Black Hole Coalescence, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We compare GW150914 directly to simulations of coalescing binary black holes in full general relativity, including several performed specifically to reproduce this event. Our calculations go beyond existing semianalytic models, because for all simulations - including sources with two independent, precessing spins - we perform comparisons which account for all the spin-weighted quadrupolar modes, and separately which account for all the quadrupolar and octopolar modes. Consistent with the posterior distributions reported by Abbott et al. [Phys. Rev. Lett. 116, 241102 (2016)] (at the 90% credible level), we find the data are compatible with a wide range of nonprecessing and …

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Comprehensive All-Sky Search For Periodic Gravitational Waves In The Sixth Science Run Ligo Data, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Aug 2016

Comprehensive All-Sky Search For Periodic Gravitational Waves In The Sixth Science Run Ligo Data, Benjamin P. Abbott, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We report on a comprehensive all-sky search for periodic gravitational waves in the frequency band 100-1500 Hz and with a frequency time derivative in the range of [-1.18,+1.00] x 10-8 Hz/s. Such a signal could be produced by a nearby spinning and slightly nonaxisymmetric isolated neutron star in our galaxy. This search uses the data from the initial LIGO sixth science run and covers a larger parameter space with respect to any past search. A Loosely Coherent detection pipeline was applied to follow up weak outliers in both Gaussian (95% recovery rate) and non-Gaussian (75% recovery rate) bands. No …

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Nonresonant Two-Photon Transitions In Length And Velocity Gauges, Ulrich D. Jentschura Aug 2016

Nonresonant Two-Photon Transitions In Length And Velocity Gauges, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

We reexamine the invariance of two-photon transition matrix elements and corresponding two-photon Rabi frequencies under the "gauge" transformation from the length to the velocity gauge. It is shown that gauge invariance, in the most general sense, only holds at exact resonance, for both one-color as well as two-color absorption. The arguments leading to this conclusion are supported by analytic calculations which express the matrix elements in terms of hypergeometric functions, and ramified by a "master identity" which is fulfilled by off-diagonal matrix elements of the Schrödinger propagator under the transformation from the velocity to the length gauge. The study of …

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Theory Of Noncontact Friction For Atom-Surface Interactions, Ulrich D. Jentschura, M. Janke, Maarten F M De Kieviet Aug 2016

Theory Of Noncontact Friction For Atom-Surface Interactions, Ulrich D. Jentschura, M. Janke, Maarten F M De Kieviet

Physics Faculty Research & Creative Works

The noncontact (van der Waals) friction is an interesting physical effect, which has been the subject of controversial scientific discussion. The direct friction term due to the thermal fluctuations of the electromagnetic field leads to a friction force proportional to 1/Z5 (where Z is the atom-wall distance). The backaction friction term takes into account the feedback of thermal fluctuations of the atomic dipole moment onto the motion of the atom and scales as 1/Z8. We investigate noncontact friction effects for the interactions of hydrogen, ground-state helium, and metastable helium atoms with α-quartz (SiO2), gold (Au), …

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Control Of Energy Density Inside A Disordered Medium By Coupling To Open Or Closed Channels, Raktim Sarma, Alexey Yamilov, Sasha Petrenko, Yaron Bromberg, Hui Cao Aug 2016

Control Of Energy Density Inside A Disordered Medium By Coupling To Open Or Closed Channels, Raktim Sarma, Alexey Yamilov, Sasha Petrenko, Yaron Bromberg, Hui Cao

Physics Faculty Research & Creative Works

We demonstrate experimentally the efficient control of light intensity distribution inside a random scattering system. The adaptive wave front shaping technique is applied to a silicon waveguide containing scattering nanostructures, and the on-chip coupling scheme enables access to all input spatial modes. By selectively coupling the incident light to the open or closed channels of the disordered system, we not only vary the total energy stored inside the system by a factor of 7.4, but also change the energy density distribution from an exponential decay to a linear decay and to a profile peaked near the center. This work provides …

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Comparison Of Experimental And Theoretical Fully Differential Cross Sections For Single Ionization Of The 2s And 2p States Of Li By O⁸⁺ Ions, Ebrahim Ghanbari-Adivi, Daniel Fischer, Natalia Ferreira, Johannes Goullon, Renate Hubele, Aaron Laforge, Michael Schulz, Don H. Madison Aug 2016

Comparison Of Experimental And Theoretical Fully Differential Cross Sections For Single Ionization Of The 2s And 2p States Of Li By O⁸⁺ Ions, Ebrahim Ghanbari-Adivi, Daniel Fischer, Natalia Ferreira, Johannes Goullon, Renate Hubele, Aaron Laforge, Michael Schulz, Don H. Madison

Physics Faculty Research & Creative Works

This paper presents a full three-dimensional (3D) comparison between experiment and theory for 24 MeV O8+ single ionization of the 2s ground state of lithium and the 2p excited state. Two theoretical approximations are examined: the three-body continuum distorted-wave (3DW) and three-body continuum distorted-wave-eikonal initial state (3DW-EIS). Normally, there is a significant difference between these two approaches and the 3DW-EIS is in much better agreement with experiment. In this case, there is very little difference between the two approaches and both are in very good agreement with experiment. For the excited 2p state, the 3D cross sections would exhibit …

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Contact Process With Temporal Disorder, Hatem Barghathi, Thomas Vojta, José A. Hoyos Aug 2016

Contact Process With Temporal Disorder, Hatem Barghathi, Thomas Vojta, José A. Hoyos

Physics Faculty Research & Creative Works

We investigate the influence of time-varying environmental noise, i.e., temporal disorder, on the nonequilibrium phase transition of the contact process. Combining a real-time renormalization group, scaling theory, and large scale Monte-Carlo simulations in one and two dimensions, we show that the temporal disorder gives rise to an exotic critical point. At criticality, the effective noise amplitude diverges with increasing time scale, and the probability distribution of the density becomes infinitely broad, even on a logarithmic scale. Moreover, the average density and survival probability decay only logarithmically with time. This infinite-noise critical behavior can be understood as the temporal counterpart of …

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Ferromagnetic Quantum Critical Point Avoided By The Appearance Of Another Magnetic Phase In Lacrge₃ Under Pressure, Valentin Taufour, Udhara S. Kaluarachchi, Rustem Khasanov, Manh Cuong Nguyen, Zurab Guguchia, Pabitra Kumar Biswas, Pietro Bonfà, Roberto De Renzi, Xiao Lin, For Full List Of Authors, See Publisher's Website. Jul 2016

Ferromagnetic Quantum Critical Point Avoided By The Appearance Of Another Magnetic Phase In Lacrge₃ Under Pressure, Valentin Taufour, Udhara S. Kaluarachchi, Rustem Khasanov, Manh Cuong Nguyen, Zurab Guguchia, Pabitra Kumar Biswas, Pietro Bonfà, Roberto De Renzi, Xiao Lin, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

The temperature-pressure phase diagram of the ferromagnet LaCrGe3 is determined for the first time from a combination of magnetization, muon-spin-rotation, and electrical resistivity measurements. The ferromagnetic phase is suppressed near 2.1 GPa, but quantum criticality is avoided by the appearance of a magnetic phase, likely modulated, AFMQ. Our density functional theory total energy calculations suggest a near degeneracy of antiferromagnetic states with small magnetic wave vectors Q allowing for the potential of an ordering wave vector evolving from Q = 0 to finite Q, as expected from the most recent theories on ferromagnetic quantum criticality. Our findings …

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