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Full-Text Articles in Physical Sciences and Mathematics

Rounding Of A First-Order Quantum Phase Transition To A Strong-Coupling Critical Point, Fawaz Hrahsheh, Jose A. Hoyos, Thomas Vojta Dec 2012

Rounding Of A First-Order Quantum Phase Transition To A Strong-Coupling Critical Point, Fawaz Hrahsheh, Jose A. Hoyos, Thomas Vojta

Physics Faculty Research & Creative Works

We investigate the effects of quenched disorder on first-order quantum phase transitions on the example of the N-color quantum Ashkin-Teller model. By means of a strong-disorder renormalization group, we demonstrate that quenched disorder rounds the first-order quantum phase transition to a continuous one for both weak and strong coupling between the colors. In the strong-coupling case, we find a distinct type of infinite-randomness critical point characterized by additional internal degrees of freedom. We investigate its critical properties in detail and find stronger thermodynamic singularities than in the random transverse field Ising chain. We also discuss the implications for higher spatial ...


Clustering Of Sloan Digital Sky Survey Iii Photometric Luminous Galaxies: The Measurement, Systematics, And Cosmological Implications, Shirley Ho, Antonio J. Cuesta, Hee-Jong Seo, Roland De Putter, Ashley J. Ross, Martin White, Nikhil Padmanabhan, Shun Saito, For Full List Of Authors, See Publisher's Website. Dec 2012

Clustering Of Sloan Digital Sky Survey Iii Photometric Luminous Galaxies: The Measurement, Systematics, And Cosmological Implications, Shirley Ho, Antonio J. Cuesta, Hee-Jong Seo, Roland De Putter, Ashley J. Ross, Martin White, Nikhil Padmanabhan, Shun Saito, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

The Sloan Digital Sky Survey (SDSS) surveyed 14,555 deg2, and delivered over a trillion pixels of imaging data. We present a study of galaxy clustering using 900,000 luminous galaxies with photometric redshifts, spanning between z = 0.45 and z = 0.65, constructed from the SDSS using methods described in Ross et al. This data set spans 11,000 deg2 and probes a volume of 3 h-3 Gpc3, making it the largest volume ever used for galaxy clustering measurements. We describe in detail the construction of the survey window function and various systematics affecting our ...


Acoustic Scale From The Angular Power Spectra Of Sdss-Iii Dr8 Photometric Luminous Galaxies, Hee-Jong Seo, Shirley Ho, Martin White, Antonio J. Cuesta, Ashley J. Ross, Shun Saito, For Full List Of Authors, See Publisher's Website. Dec 2012

Acoustic Scale From The Angular Power Spectra Of Sdss-Iii Dr8 Photometric Luminous Galaxies, Hee-Jong Seo, Shirley Ho, Martin White, Antonio J. Cuesta, Ashley J. Ross, Shun Saito, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We measure the acoustic scale from the angular power spectra of the Sloan Digital Sky Survey III (SDSS-III) Data Release 8 imaging catalog that includes 872, 921 galaxies over ~10,000 deg2 between 0.45 < z < 0.65. The extensive spectroscopic training set of the Baryon Oscillation Spectroscopic Survey luminous galaxies allows precise estimates of the true redshift distributions of galaxies in our imaging catalog. Utilizing the redshift distribution information, we build templates and fit to the power spectra of the data, which are measured in our companion paper, to derive the location of Baryon acoustic oscillations (BAOs) while marginalizing over many free parameters to exclude nearly all of the non-BAO signal. We derive the ratio of the angular diameter distance to the sound horizon scale DA(z)/rs = 9.212+0.416-0.404 at z = 0.54, and therefore DA (z) = 1411 ± 65 Mpc at z = 0.54; the result is fairly independent of assumptions on the underlying cosmology. Our measurement of angular diameter distance DA(z) is 1.4σ higher than what is expected for the concordance ΛCDM, in accordance to the trend of other ...


Disordered Bosons In One Dimension: From Weak- To Strong-Randomness Criticality, Fawaz Hrahsheh, Thomas Vojta Dec 2012

Disordered Bosons In One Dimension: From Weak- To Strong-Randomness Criticality, Fawaz Hrahsheh, Thomas Vojta

Physics Faculty Research & Creative Works

We investigate the superfluid-insulator quantum phase transition of one-dimensional bosons with off-diagonal disorder by means of large-scale Monte Carlo simulations. For weak disorder, we find the transition to be in the same universality class as the superfluid-Mott insulator transition of the clean system. The nature of the transition changes for stronger disorder. Beyond a critical disorder strength, we find nonuniversal, disorder-dependent critical behavior. We compare our results to recent perturbative and strong-disorder renormalization group predictions. We also discuss experimental implications as well as extensions of our results to other systems.


Laser-Induced Electron Diffraction For Probing Rare Gas Atoms, Junliang Xu, Cosmin I. Blaga, Anthony D. Dichiara, Emily Sistrunk, Kaikai Zhang, Zhangjin Chen, Anh-Thu Le, Toru Morishita, C. D. Lin, Pierre Agostini, Louis F. Dimauro Dec 2012

Laser-Induced Electron Diffraction For Probing Rare Gas Atoms, Junliang Xu, Cosmin I. Blaga, Anthony D. Dichiara, Emily Sistrunk, Kaikai Zhang, Zhangjin Chen, Anh-Thu Le, Toru Morishita, C. D. Lin, Pierre Agostini, Louis F. Dimauro

Physics Faculty Research & Creative Works

Recently, using midinfrared laser-induced electron diffraction (LIED), snapshots of a vibrating diatomic molecule on a femtosecond time scale have been captured [C.I. Blaga et al., Nature (London) 483, 194 (2012)]. In this Letter, a comprehensive treatment for the atomic LIED response is reported, a critical step in generalizing this imaging method. Electron-ion differential cross sections (DCSs) of rare gas atoms are extracted from measured angular-resolved, high-energy electron momentum distributions generated by intense midinfrared lasers. Following strong-field ionization, the high-energy electrons result from elastic rescattering of a field-driven wave packet with the parent ion. For recollision energies [greater or equal ...


Theory Of High Harmonic Generation For Probing Time-Resolved Large-Amplitude Molecular Vibrations With Ultrashort Intense Lasers, Anh-Thu Le, Toru Morishita, R. R. Lucchese, C. D. Lin Nov 2012

Theory Of High Harmonic Generation For Probing Time-Resolved Large-Amplitude Molecular Vibrations With Ultrashort Intense Lasers, Anh-Thu Le, Toru Morishita, R. R. Lucchese, C. D. Lin

Physics Faculty Research & Creative Works

We present a theory that incorporates the vibrational degrees of freedom in a high-order harmonic generation (HHG) process with ultrashort intense laser pulses. In this model, laser-induced time-dependent transition dipoles for each fixed molecular geometry are added coherently, weighted by the laser-driven time-dependent nuclear wave packet distribution. We show that the nuclear distribution can be strongly modified by the HHG driving laser. The validity of this model is first checked against results from the numerical solution of the time-dependent Schrödinger equation for a simple model system. We show that in combination with the established quantitative rescattering theory this model is ...


Swift Follow-Up Observations Of Candidate Gravitational-Wave Transient Events, P. A. Evans, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Nov 2012

Swift Follow-Up Observations Of Candidate Gravitational-Wave Transient Events, P. A. Evans, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present the first multi-wavelength follow-up observations of two candidate gravitational-wave (GW) transient events recorded by LIGO and Virgo in their 2009-2010 science run. The events were selected with low latency by the network of GW detectors (within less than 10 minutes) and their candidate sky locations were observed by the Swift observatory (within 12 hr). Image transient detection was used to analyze the collected electromagnetic data, which were found to be consistent with background. Off-line analysis of the GW data alone has also established that the selected GW events show no evidence of an astrophysical origin; one of them ...


Monte Carlo Simulations Of The Clean And Disordered Contact Process In Three Dimensions, Thomas Vojta Nov 2012

Monte Carlo Simulations Of The Clean And Disordered Contact Process In Three Dimensions, Thomas Vojta

Physics Faculty Research & Creative Works

The absorbing-state transition in the three-dimensional contact process with and without quenched randomness is investigated by means of Monte Carlo simulations. In the clean case, a reweighting technique is combined with a careful extrapolation of the data to infinite time to determine with high accuracy the critical behavior in the three-dimensional directed percolation universality class. In the presence of quenched spatial disorder, our data demonstrate that the absorbing-state transition is governed by an unconventional infinite-randomness critical point featuring activated dynamical scaling. The critical behavior of this transition does not depend on the disorder strength, i.e., it is universal. Close ...


Quantum Dynamics In Atomic-Fountain Experiments For Measuring The Electric Dipole Moment Of The Electron With Improved Sensitivity, Benedikt J. Wundt, Charles T. Munger, Ulrich D. Jentschura Nov 2012

Quantum Dynamics In Atomic-Fountain Experiments For Measuring The Electric Dipole Moment Of The Electron With Improved Sensitivity, Benedikt J. Wundt, Charles T. Munger, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

An improved measurement of the electron electric dipole moment (EDM) appears feasible using groundstate alkali atoms in an atomic fountain in which a strong electric field, which couples to a conceivable EDM, is applied perpendicular to the fountain axis. In a practical fountain, the ratio of the atomic tensor Stark shift to the Zeeman shift is a factor μ ~ 100.We expand the complete time-evolution operator in inverse powers of this ratio; complete results are presented for atoms of total spin F = 3, 4, and 5. For a specific set of entangled hyperfine sublevels (coherent states), potential systematic errors enter ...


Random Fields At A Nonequilibrium Phase Transition, Hatem Barghathi, Thomas Vojta Oct 2012

Random Fields At A Nonequilibrium Phase Transition, Hatem Barghathi, Thomas Vojta

Physics Faculty Research & Creative Works

We study nonequilibrium phase transitions in the presence of disorder that locally breaks the symmetry between two equivalent macroscopic states. In low-dimensional equilibrium systems, such random-field disorder is known to have dramatic effects: it prevents spontaneous symmetry breaking and completely destroys the phase transition. In contrast, we show that the phase transition of the one-dimensional generalized contact process persists in the presence of random-field disorder. The ultraslow dynamics in the symmetry-broken phase is described by a Sinai walk of the domain walls between two different absorbing states. We discuss the generality and limitations of our theory, and we illustrate our ...


Search For Gravitational Waves Associated With Gamma-Ray Bursts During Ligo Science Run 6 And Virgo Science Runs 2 And 3, J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Oct 2012

Search For Gravitational Waves Associated With Gamma-Ray Bursts During Ligo Science Run 6 And Virgo Science Runs 2 And 3, J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present the results of a search for gravitational waves associated with 154 gamma-ray bursts (GRBs) that were detected by satellite-based gamma-ray experiments in 2009-2010, during the sixth LIGO science run and the second and third Virgo science runs. We perform two distinct searches: a modeled search for coalescences of either two neutron stars or a neutron star and black hole, and a search for generic, unmodeled gravitational-wave bursts. We find no evidence for gravitational-wave counterparts, either with any individual GRB in this sample or with the population as a whole. For all GRBs we place lower bounds on the ...


Erratum: Search For Gravitational Waves From Binary Black Hole Inspiral, Merger, And Ringdown (Physical Review D - Particles, Fields, Gravitation And Cosmology (2011) 83 (122005)), J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Sep 2012

Erratum: Search For Gravitational Waves From Binary Black Hole Inspiral, Merger, And Ringdown (Physical Review D - Particles, Fields, Gravitation And Cosmology (2011) 83 (122005)), J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

Since the publication we have discovered two errors in the calculation of upper limits on binary black hole (BBH) coalescence rates inferred from the nondetection of gravitational waves. The errors caused systematic biases of opposite signs and different sizes in the 90% confidence rate limits; when errors are corrected, the resulting limits are a factor 3 to 5 smaller than those quoted. Here we give a brief description of the errors and report their impacts on the upper limit results.


Non-Fermi Liquid Transport And "Universal" Ratios In Quantum Griffiths Phases, David Nozadze, Thomas Vojta Sep 2012

Non-Fermi Liquid Transport And "Universal" Ratios In Quantum Griffiths Phases, David Nozadze, Thomas Vojta

Physics Faculty Research & Creative Works

We use the semi-classical Boltzmann equation to investigate transport properties such as electrical resistivity, thermal resistivity, thermopower, and the Peltier coefficient of disordered metals close to an antiferromagnetic quantum phase transition. In the quantum Griffiths phase, the electrons are scattered by spin-fluctuations in the rare regions. This leads to singular temperature dependencies not just at the quantum critical point, but in the entire Griffiths phase. We show that the resulting non-universal power-laws in transport properties are controlled by the same Griffiths exponent λ which governs the thermodynamics. λ takes the value zero at the quantum critical point and increases throughout ...


Ion-Lithium Collision Dynamics Studied With A Laser-Cooled In-Ring Target, Daniel Fischer, Dominik Globig, Johannes Goullon, Manfred Grieser, Renate Hubele, Vitor L B D De Jesus, Aditya H. Kelkar, Aaron C. Laforge, H. Lindenblatt, Deepankar S. Misra, B. Najjari, Katharina R. Schneider, Michael Schulz, Martin Sell, Xincheng Wang Sep 2012

Ion-Lithium Collision Dynamics Studied With A Laser-Cooled In-Ring Target, Daniel Fischer, Dominik Globig, Johannes Goullon, Manfred Grieser, Renate Hubele, Vitor L B D De Jesus, Aditya H. Kelkar, Aaron C. Laforge, H. Lindenblatt, Deepankar S. Misra, B. Najjari, Katharina R. Schneider, Michael Schulz, Martin Sell, Xincheng Wang

Physics Faculty Research & Creative Works

We present a novel experimental tool allowing for kinematically complete studies of break-up processes of laser-cooled atoms. This apparatus, the 'MOTReMi,' is a combination of a magneto-optical trap (MOT) and a reaction microscope (ReMi). Operated in an ion-storage ring, the new setup enables us to study the dynamics in swift ion-atom collisions on an unprecedented level of precision and detail. In the inaugural experiment on collisions with 1.5MeV/amu O8 +-Li the pure ionization of the valence electron as well as the ionization-excitation of the lithium target was investigated.


Erratum: Triple Compton Effect: A Photon Splitting Into Three Upon Collision With A Free Electron (Physical Review Letters (2012) 108 (233201)), Erik Loetstedt, Ulrich D. Jentschura Aug 2012

Erratum: Triple Compton Effect: A Photon Splitting Into Three Upon Collision With A Free Electron (Physical Review Letters (2012) 108 (233201)), Erik Loetstedt, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

No abstract provided.


Quantum Electrodynamic Corrections To The G Factor Of Helium P States, Mariusz Puchalski, Ulrich D. Jentschura Aug 2012

Quantum Electrodynamic Corrections To The G Factor Of Helium P States, Mariusz Puchalski, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

The Landég factor describes the response of an atomic energy level to an external perturbation by a uniform and constant magnetic field. In the case of many-electron systems, the leading term is given by the interaction μ B(L- +2S- )•B- , where L- and S- are the orbital and spin angular momentum operators, respectively, summed over all electrons. For helium, a long-standing experimental-theoretical discrepancy for P states motivates a re-evaluation of the higher order terms which follow from relativistic quantum theory and quantum electrodynamics (QED). The tensor structure of relativistic corrections involves scalar, vector, and symmetric and antisymmetric tensor components ...


Percolation Transition In Quantum Ising And Rotor Models With Sub-Ohmic Dissipation, Manal Al-Ali, Jose Abel Hoyos, Thomas Vojta Aug 2012

Percolation Transition In Quantum Ising And Rotor Models With Sub-Ohmic Dissipation, Manal Al-Ali, Jose Abel Hoyos, Thomas Vojta

Physics Faculty Research & Creative Works

We investigate the influence of sub-Ohmic dissipation on randomly diluted quantum Ising and rotor models. The dissipation causes the quantum dynamics of sufficiently large percolation clusters to freeze completely. As a result, the zero-temperature quantum phase transition across the lattice percolation threshold separates an unusual super-paramagnetic cluster phase from an inhomogeneous ferromagnetic phase. We determine the low-temperature thermodynamic behavior in both phases, which is dominated by large frozen and slowly fluctuating percolation clusters. We relate our results to the smeared transition scenario for disordered quantum phase transitions, and we compare the cases of sub-Ohmic, Ohmic, and super-Ohmic dissipation.


Three-Body Dynamics In Single Ionization Of Atomic Hydrogen By 75 Kev Proton Impact, Aaron Laforge, Kisra Egodapitiya, Sachin Sharma, Michael Schulz Aug 2012

Three-Body Dynamics In Single Ionization Of Atomic Hydrogen By 75 Kev Proton Impact, Aaron Laforge, Kisra Egodapitiya, Sachin Sharma, Michael Schulz

Physics Faculty Research & Creative Works

We have measured and calculated doubly differential cross sections for ionization of atomic hydrogen using 75-keV proton impact for fixed projectile energy losses as a function of scattering angle.


Projectile Coherence Effects In Electron Capture By Protons Colliding With H₂ And He, Sachin D. Sharma, Ahmad Hasan, Kisra N. Egodapitiya, T. P. Arthanayaka, G. Sakhelashvili, Michael Schulz Aug 2012

Projectile Coherence Effects In Electron Capture By Protons Colliding With H₂ And He, Sachin D. Sharma, Ahmad Hasan, Kisra N. Egodapitiya, T. P. Arthanayaka, G. Sakhelashvili, Michael Schulz

Physics Faculty Research & Creative Works

We have measured differential cross sections for single and dissociative capture for 25 and 75 keV protons colliding with H2 and He. Significant differences were found depending on whether the projectile beam was coherent or incoherent. For 75 keV p+H2 these differences can be mostly associated with molecular two-center interference and possibly some contributions from path interference. For 25 keV (both targets) they are mostly due to path interference between different impact parameters leading to the same scattering angles and, for the H2 target, possibly some contributions from molecular two-center interference.


Composition-Dependent Oxygen Vacancy Formation In Multicomponent Wide-Band-Gap Oxides, Altynbek Murat, Julia E. Medvedeva Aug 2012

Composition-Dependent Oxygen Vacancy Formation In Multicomponent Wide-Band-Gap Oxides, Altynbek Murat, Julia E. Medvedeva

Physics Faculty Research & Creative Works

The formation and distribution of oxygen vacancy in layered multicomponent InAMO 4 oxides with A3 +=Al or Ga and M2 +=Ca or Zn and in the corresponding binary oxide constituents is investigated using first-principles density functional calculations. Comparing the calculated formation energies of the oxygen defect at six different site locations within the structurally and chemically distinct layers of InAMO 4 oxides, we find that the vacancy distribution is significantly affected not only by the strength of the metal-oxygen bonding, but also by the cation's ability to adjust to anisotropic oxygen environment created by the vacancy. In particular, the ...


Four Body Charge Transfer Process In Proton Helium Collision, Ujjal Chowdhury, Allison L. Harris, Jerry Peacher, Don H. Madison Jul 2012

Four Body Charge Transfer Process In Proton Helium Collision, Ujjal Chowdhury, Allison L. Harris, Jerry Peacher, Don H. Madison

Physics Faculty Research & Creative Works

Recent advancements in experimental techniques now allow for the study of fully differential cross sections for 4-body collisions. Theoretical fully differential cross sections will be presented and compared with absolute experimental data for transfer-excitation in proton-helium collisions. The role of different scattering mechanism will be discussed.


Implications For The Origin Of Grb 051103 From Ligo Observations, J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Jul 2012

Implications For The Origin Of Grb 051103 From Ligo Observations, J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

We present the results of a LIGO search for gravitational waves (GWs) associated with GRB 051103, a short-duration hard-spectrum gamma-ray burst (GRB) whose electromagnetically determined sky position is coincident with the spiral galaxy M81, which is 3.6 Mpc from Earth. Possible progenitors for short-hard GRBs include compact object mergers and soft gamma repeater (SGR) giant flares. A merger progenitor would produce a characteristic GW signal that should be detectable at a distance of M81, while GW emission from an SGR is not expected to be detectable at that distance. We found no evidence of a GW signal associated with ...


Low Energy (E, 2e) Study From The 1t₂ Orbital Of Ch₄, Shenyue Xu, Hari Chaluvadi, Xueguang Ren, Thomas Pfluger, Arne Senftleben, Chuangang Ning, Shuncheng Yan, Peng Zhang, Jie Yang, Xinwen Ma, Joachim Hermann Ullrich, Don H. Madison, Alexander Dorn Jul 2012

Low Energy (E, 2e) Study From The 1t₂ Orbital Of Ch₄, Shenyue Xu, Hari Chaluvadi, Xueguang Ren, Thomas Pfluger, Arne Senftleben, Chuangang Ning, Shuncheng Yan, Peng Zhang, Jie Yang, Xinwen Ma, Joachim Hermann Ullrich, Don H. Madison, Alexander Dorn

Physics Faculty Research & Creative Works

Single ionization of the methane (CH4) 1t2 orbital by 54 eV electron impact has been studied experimentally and theoretically. The measured triple differential cross sections cover nearly a 4π solid angle for the emission of low energy electrons and a range of projectile scattering angles. Experimental data are compared with theoretical calculations from the distorted wave Born approximation and the molecular three-body distorted wave models. It is found that theory can give a proper description of the main features of experimental cross section only at smaller scattering angles. For larger scattering angles, significant discrepancies between experiment and theory ...


Conditions For Extracting Photoionization Cross Sections From Laser-Induced High-Order-Harmonic Spectra, Guoli Wang, Cheng Jin, Anh-Thu Le, C. D. Lin Jul 2012

Conditions For Extracting Photoionization Cross Sections From Laser-Induced High-Order-Harmonic Spectra, Guoli Wang, Cheng Jin, Anh-Thu Le, C. D. Lin

Physics Faculty Research & Creative Works

We show that photoionization cross sections of atoms can be accurately extracted from the high-order-harmonic spectra generated by intense infrared lasers only if the degree of ionization in the gas medium is small, implying that for this purpose the high-order-harmonic generation spectra should be taken at low gas pressure and at low laser intensity experimentally.


Fully Differential Cross Section For Four Body Charge Transfer Process, Ujjal Chowdhury, Allison L. Harris, Jerry Peacher, Don H. Madison Jul 2012

Fully Differential Cross Section For Four Body Charge Transfer Process, Ujjal Chowdhury, Allison L. Harris, Jerry Peacher, Don H. Madison

Physics Faculty Research & Creative Works

Recently experimental fully differential cross sections (FDCS) have been reported for double capture in proton helium collisions which disagree with existing theoretical calculations by two orders of magnitude. We introduce here a theoretical model for charge transfer processes which is fully quantum mechanical and takes all post collision interactions (PCI) between the particles into account exactly. The results of this model are in much better agreement with experimental data.


All-Sky Search For Gravitational-Wave Bursts In The Second Joint Ligo-Virgo Run, J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Jun 2012

All-Sky Search For Gravitational-Wave Bursts In The Second Joint Ligo-Virgo Run, J. Abadie, 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 in the data collected by the LIGO and Virgo detectors between July 7, 2009 and October 20, 2010: data are analyzed when at least two of the three LIGO-Virgo detectors are in coincident operation, with a total observation time of 207 days. The analysis searches for transients of duration ≲ 1 s over the frequency band 64-5000 Hz, without other assumptions on the signal waveform, polarization, direction or occurrence time. All identified events are consistent with the expected accidental background. We set frequentist upper limits on the rate of gravitational-wave bursts by ...


Triple Compton Effect: A Photon Splitting Into Three Upon Collision With A Free Electron, Erik Loetstedt, Ulrich D. Jentschura Jun 2012

Triple Compton Effect: A Photon Splitting Into Three Upon Collision With A Free Electron, Erik Loetstedt, Ulrich D. Jentschura

Physics Faculty Research & Creative Works

The process in which a photon splits into three after the collision with a free electron (triple Compton effect) is the most basic process for the generation of a high-energy multiparticle entangled state composed out of elementary quanta. The cross section of the process is evaluated in two experimentally realizable situations, one employing gamma photons and stationary electrons, and the other using keV photons and GeV electrons of an x-ray free electron laser. For the first case, our calculation is in agreement with the only available measurement of the differential cross section for the process under study. Our estimates indicate ...


Upper Limits On A Stochastic Gravitational-Wave Background Using Ligo And Virgo Interferometers At 600-1000 Hz, J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. Jun 2012

Upper Limits On A Stochastic Gravitational-Wave Background Using Ligo And Virgo Interferometers At 600-1000 Hz, J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

A stochastic background of gravitational waves is expected to arise from a superposition of many incoherent sources of gravitational waves, of either cosmological or astrophysical origin. This background is a target for the current generation of ground-based detectors. In this article we present the first joint search for a stochastic background using data from the LIGO and Virgo interferometers. In a frequency band of 600-1000 Hz, we obtained a 95% upper limit on the amplitude of ΩGW(f) = Ω3(f/900Hz)3, of Ω3 < 0.32, assuming a value of the Hubble parameter of h100 = 0.71. These new limits are a factor of seven better than ...


Dissipation Effects In Random Transverse-Field Ising Chains, Jose A. Hoyos, Thomas Vojta May 2012

Dissipation Effects In Random Transverse-Field Ising Chains, Jose A. Hoyos, Thomas Vojta

Physics Faculty Research & Creative Works

We study the effects of Ohmic, super-Ohmic, and sub-Ohmic dissipation on the zero-temperature quantum phase transition in the random transverse-field Ising chain by means of an (asymptotically exact) analytical strong-disorder renormalization-group approach. We find that Ohmic damping destabilizes the infinite-randomness critical point and the associated quantum Griffiths singularities of the dissipationless system. The quantum dynamics of large magnetic clusters freezes completely, which destroys the sharp phase transition by smearing. The effects of sub-Ohmic dissipation are similar and also lead to a smeared transition. In contrast, super-Ohmic damping is an irrelevant perturbation; the critical behavior is thus identical to that of ...


First Low-Latency Ligo+Virgo Search For Binary Inspirals And Their Electromagnetic Counterparts, J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website. May 2012

First Low-Latency Ligo+Virgo Search For Binary Inspirals And Their Electromagnetic Counterparts, J. Abadie, Marco Cavaglia, For Full List Of Authors, See Publisher's Website.

Physics Faculty Research & Creative Works

Aims. The detection and measurement of gravitational-waves from coalescing neutron-star binary systems is an important science goal for ground-based gravitational-wave detectors. In addition to emitting gravitational-waves at frequencies that span the most sensitive bands of the LIGO and Virgo detectors, these sources are also amongst the most likely to produce an electromagnetic counterpart to the gravitational-wave emission. A joint detection of the gravitational-wave and electromagnetic signals would provide a powerful new probe for astronomy. Methods. During the period between September 19 and October 20, 2010, the first low-latency search for gravitational-waves from binary inspirals in LIGO and Virgo data was ...