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Full-Text Articles in Physics
Long Distance Effects And Strangeness In The Nucleon, John Donoghue, Barry R. Holstein, Tobias Huber, Andreas Ross
Long Distance Effects And Strangeness In The Nucleon, John Donoghue, Barry R. Holstein, Tobias Huber, Andreas Ross
John Donoghue
We discuss the calculation of the strange magnetic radius of the proton in chiral perturbation theory. In particular we investigate the low energy component of the loop integrals involving kaons. We separate the chiral calculation into a low energy part and a high energy component through use of a momentum space separation scale. This separation shows that most of the chiral calculation comes from high energies where the effective field theory treatment is not valid. The resulting low energy prediction is in better agreement with dispersive treatments. Finally, we briefly discuss magnetic moments and show how our techniques can help …
Observation Of A Metallic Superfluid In A Numerical Experiment, E. Smorgrav, J. Smiseth, Egor Babaev, A. Sudbo
Observation Of A Metallic Superfluid In A Numerical Experiment, E. Smorgrav, J. Smiseth, Egor Babaev, A. Sudbo
Egor Babaev
We report the observation, in Monte Carlo simulations, of a novel type of quantum ordered state: {\it the metallic superfluid}. The metallic superfluid features ohmic resistance to counter-flows of protons and electrons, while featuring dissipationless co-flows of electrons and protons. One of the candidates for a physical realization of this remarkable state of matter is hydrogen or its isotopes under high compression. This adds another potential candidate to the presently known quantum dissipationless states, namely superconductors, superfluid liquids and vapours, and supersolids.
Observability Of A Projected New State Of Matter: A Metallic Superfluid, Egor Babaev, Asle Sudbo, N. W. Ashcroft
Observability Of A Projected New State Of Matter: A Metallic Superfluid, Egor Babaev, Asle Sudbo, N. W. Ashcroft
Egor Babaev
Dissipationless quantum states, such as superconductivity and superfluidity, have attracted interest for almost a century. A variety of systems exhibit these macroscopic quantum phenomena, ranging from superconducting electrons in metals to superfluid liquids, atomic vapours, and even large nuclei. It was recently suggested that liquid metallic hydrogen could form two new unusual dissipationless quantum states, namely the metallic superfluid and the superconducting superfluid. Liquid metallic hydrogen is projected to occur only at an extremely high pressure of about 400 GPa, while pressures on hydrogen of 320 GPa having already been reported. The issue to be adressed is if this state …
An Effective Theory Of Initial Conditions In Inflation, Hael Collins, R. Holman
An Effective Theory Of Initial Conditions In Inflation, Hael Collins, R. Holman
Physics Department Faculty Publication Series
We examine the renormalization of an effective theory description of a general initial state set in an isotropically expanding space-time, which is done to understand how to include the effects of new physics in the calculation of the cosmic microwave background power spectrum. The divergences that arise in a perturbative treatment of the theory are of two forms: those associated with the properties of a field propagating through the bulk of space-time, which are unaffected by the choice of the initial state, and those that result from summing over the short-distance structure of the initial state. We show that the …
Isotropy Of The Early Universe From Cmb Anisotropies, Evan P. Donoghue, John Donoghue
Isotropy Of The Early Universe From Cmb Anisotropies, Evan P. Donoghue, John Donoghue
John Donoghue
The acoustic peak in the CMB power spectrum is sensitive to causal processes and cosmological parameters in the early universe up to the time of last scattering. We provide limits on correlated spatial variations of the peak height and peak position and interpret these as constraints on the spatial variation of the cosmological parameters (baryon density, cold dark matter density and cosmological constant as well as the amplitude and tilt of the original fluctuations). We utilize recent work of Hansen, Banday and Gorski (HBG) who have studied the spatial isotropy of the power spectrum as measured by WMAP by performing …
Renormalization Of Initial Conditions And The Trans-Planckian Problem Of Inflation, Hael Collins, R. Holman
Renormalization Of Initial Conditions And The Trans-Planckian Problem Of Inflation, Hael Collins, R. Holman
Physics Department Faculty Publication Series
No abstract provided.
Department Of Physics Newsletter: Spring 2005, Bob Krotkov, Gerry Peterson, Monroe Rabin, Hajime Sakai
Department Of Physics Newsletter: Spring 2005, Bob Krotkov, Gerry Peterson, Monroe Rabin, Hajime Sakai
Physics Newsletters
No abstract provided.
Supersolid Phase Of Hard-Core Bosons On A Triangular Lattice, M Boninsegni, Nikolai Prokof'ev
Supersolid Phase Of Hard-Core Bosons On A Triangular Lattice, M Boninsegni, Nikolai Prokof'ev
Physics Department Faculty Publication Series
We study properties of the supersolid phase observed for hard-core bosons on the triangular lattice near half-integer filling factor, and the phase diagram of the system at finite temperature. We find that the solid order is always of the (2m,-m′,-m′) with m changing discontinuously from positive to negative values at half filling, in contrast with phases observed for Ising spins in a transverse magnetic field. At finite temperature we find two intersecting second-order transition lines: one in the 3-state Potts universality class and the other of the Kosterlitz-Thouless type.
Superfluid Interfaces In Quantum Solids, E Bourovski, E. Kozik, A Kuklov, Nikolai Prokof'ev, Boris Svistunov
Superfluid Interfaces In Quantum Solids, E Bourovski, E. Kozik, A Kuklov, Nikolai Prokof'ev, Boris Svistunov
Physics Department Faculty Publication Series
One scenario for the nonclassical moment of inertia of solid 4He discovered by Kim and Chan [Nature (London) 427, 225 (2004)] is the superfluidity of microcrystallite interfaces. On the basis of the most simple model of a quantum crystal—the checkerboard lattice solid—we show that the superfluidity of interfaces between solid domains can exist in a wide range of parameters. At strong enough interparticle interaction, a superfluid interface becomes an insulator via a quantum phase transition. Under the conditions of particle-hole symmetry, the transition is of the standard U(1) universality class in 3D, while in 2D the onset of superfluidity is …
Reply To “Comment On ‘Hole Digging In Ensembles Of Tunneling Molecular Magnets’ ”, I Tupitsyn, P Stamp, Nikolai Prokof'ev
Reply To “Comment On ‘Hole Digging In Ensembles Of Tunneling Molecular Magnets’ ”, I Tupitsyn, P Stamp, Nikolai Prokof'ev
Physics Department Faculty Publication Series
Our work has argued for a particular scaling form governing the distribution M(ξ,t) of magnetization over bias ξ, for a system of dipolar-interacting molecular spins. This form, which was found in Monte Carlo (MC) simulations, leads inevitably to a short-time form ∼t1∕2 for the magnetization relaxation in the system. The authors of the Comment argue that the magnetization should decay rather as ∼tp, with the exponent p depending on the lattice type—and they argue this form is valid up to infinite times. They also claim that our conclusion is based on an assumed exponential dependence of the function M(ξ,t) on …
Scale-Separation Scheme For Simulating Superfluid Turbulence: Kelvin-Wave Cascade, E Kozik, Boris Svistunov
Scale-Separation Scheme For Simulating Superfluid Turbulence: Kelvin-Wave Cascade, E Kozik, Boris Svistunov
Physics Department Faculty Publication Series
A Kolmogorov-type cascade of Kelvin waves—the distortion waves on vortex lines—plays a key part in the relaxation of superfluid turbulence at low temperatures. We propose an efficient numeric scheme for simulating the Kelvin-wave cascade on a single vortex line. This idea is likely to be generalizable for a full-scale simulation of different regimes of superfluid turbulence. With the new scheme, we are able to unambiguously resolve the cascade spectrum exponent, and thus to settle the controversy between recent simulations of Vinen, Tsubota, and Mitani [Phys. Rev. Lett. 91, 135301 (2003)] and recently developed analytic theory [Phys. Rev. Lett. 92, 035301 …
Positivity Bounds For The Yano-Arnowitt-Deser-Misner Mass Density, David Kastor, T Shiromizu, S Tomizawa, Jennie Traschen
Positivity Bounds For The Yano-Arnowitt-Deser-Misner Mass Density, David Kastor, T Shiromizu, S Tomizawa, Jennie Traschen
Physics Department Faculty Publication Series
Killing-Yano tensors are natural generalizations of Killing vectors to arbitrary rank antisymmetric tensor fields. It was recently shown that Killing-Yano tensors lead to conserved gravitational charges, called Yano-Arnowitt-Deser-Misner (Y-ADM) charges. These new charges are interesting because they measure e.g. the mass density of a p-brane, rather than the total ADM mass which may be infinite. In this paper, we show that the spinorial techniques used by Witten, in his proof of the positive energy theorem, may be straightforwardly extended to study the positivity properties of the Y-ADM mass density for p-brane spacetimes. Although the resulting formalism is quite similar to …
Isotropy Of The Early Universe From Cmb Anisotropies, Ep Donoghue, Jf Donoghue
Isotropy Of The Early Universe From Cmb Anisotropies, Ep Donoghue, Jf Donoghue
Physics Department Faculty Publication Series
The acoustic peak in the cosmic microwave background power spectrum is sensitive to causal processes and cosmological parameters in the early universe up to the time of last scattering. We provide limits on correlated spatial variations of the peak height and peak position and interpret these as constraints on the spatial variation of the cosmological parameters (baryon density, cold dark matter density, and cosmological constant as well as the amplitude and tilt of the original fluctuations). We utilize recent work of Hansen, Banday, and Górski who have studied the spatial isotropy of the power spectrum as measured by WMAP by …
An Eft For The Weak Lambda N Interaction, A Parreno, C Bennhold, Br Holstein
An Eft For The Weak Lambda N Interaction, A Parreno, C Bennhold, Br Holstein
Physics Department Faculty Publication Series
The nonleptonic weak |ΔS|=1 ΛN interaction, responsible for the dominant, nonmesonic decay of all but the lightest hypernuclei, is studied in the framework of an effective field theory. The long-range physics is described through tree-level exchange of the SU(3) Goldstone bosons (π and K), while the short-range potential is parametrized in terms of lowest-order contact terms obtained from the most general non-derivative local four-fermion interaction. Fitting to available weak hypernuclear decay rates for 5ΛHe, 11ΛB and 12ΛC yields reasonable values for the low-energy constants.
Stationary States And Energy Cascades In Inelastic Gases, E. Ben-Naim, Jonathan Machta
Stationary States And Energy Cascades In Inelastic Gases, E. Ben-Naim, Jonathan Machta
Jonathan Machta
We find a general class of nontrivial stationary states in inelastic gases where, due to dissipation, energy is transferred from large velocity scales to small velocity scales. These steady states exist for arbitrary collision rules and arbitrary dimension. Their signature is a stationary velocity distribution f(v) with an algebraic high-energy tail, f(v)∼v−σ. The exponent σ is obtained analytically and it varies continuously with the spatial dimension, the homogeneity index characterizing the collision rate, and the restitution coefficient. We observe these stationary states in numerical simulations in which energy is injected into the system by infrequently boosting particles to high velocities. …
Parallel Dynamics And Computational Complexity Of Network Growth Models, Benjamin Machta, Jonathan Machta
Parallel Dynamics And Computational Complexity Of Network Growth Models, Benjamin Machta, Jonathan Machta
Jonathan Machta
The parallel computational complexity or depth of growing network models is investigated. The networks considered are generated by preferential attachment rules where the probability of attaching a new node to an existing node is given by a power α of the connectivity of the existing node. Algorithms for generating growing networks very quickly in parallel are described and studied. The sublinear and superlinear cases require distinct algorithms. As a result, there is a discontinuous transition in the parallel complexity of sampling these networks corresponding to the discontinuous structural transition at α=1, where the networks become scale-free. For α>1, networks …
Power-Law Velocity Distributions In Granular Gases, E. Ben-Naim, B. Machta, Jonathan Machta
Power-Law Velocity Distributions In Granular Gases, E. Ben-Naim, B. Machta, Jonathan Machta
Jonathan Machta
The kinetic theory of granular gases is studied for spatially homogeneous systems. At large velocities, the equation governing the velocity distribution becomes linear, and it admits stationary solutions with a power-law tail, f(v)∼v−σ. This behavior holds in arbitrary dimension for arbitrary collision rates including both hard spheres and Maxwell molecules. Numerical simulations show that driven steady states with the same power-law tail can be realized by injecting energy into the system at very high energies. In one dimension, we also obtain self-similar time-dependent solutions where the velocities collapse to zero. At small velocities there is a steady state and a …
Precision Measurement Of The Weak Mixing Angle In Moller Scattering, P. L. Anthony, R. G. Arnold, C. Arroyo, K. Bega, J. Biesiada, P. E. Bosted, G. Bower, J. Cahoon, R. Carr, G. D. Cates, J. P. Chen, E. Chudakov, M. Cooke, P. Decowski, A. Deur, W. Emam, R. Erickson, T. Fieguth, C. Field, J. Gao, M. Gary, K. Gustafsson, R. S. Hicks, R. Holmes, E. W. Hughes, T. B. Humensky, G. M. Jones, L. J. Kaufman, L. Keller, Yu G. Kolomensky, Krishna Kumar, P. Laviolette, D. Lhuillier, R. M. Lombard-Nelsen, Z. Marshall, P. Mastromarino, R. D. Mckeown, R. Michaels, J. Niedziela, M. Olson, K. D. Pashke, G. A. Peterson, R. Pitthan, D. Relyea, S. E. Rock, O. Saxton, J. Singh, P. A. Souder, Z. M. Szalata, J. Turner, B. Tweedie, A. Vacharet, D. Walz, T. Weber, J. Weisend, M. Woods, I. Younus
Precision Measurement Of The Weak Mixing Angle In Moller Scattering, P. L. Anthony, R. G. Arnold, C. Arroyo, K. Bega, J. Biesiada, P. E. Bosted, G. Bower, J. Cahoon, R. Carr, G. D. Cates, J. P. Chen, E. Chudakov, M. Cooke, P. Decowski, A. Deur, W. Emam, R. Erickson, T. Fieguth, C. Field, J. Gao, M. Gary, K. Gustafsson, R. S. Hicks, R. Holmes, E. W. Hughes, T. B. Humensky, G. M. Jones, L. J. Kaufman, L. Keller, Yu G. Kolomensky, Krishna Kumar, P. Laviolette, D. Lhuillier, R. M. Lombard-Nelsen, Z. Marshall, P. Mastromarino, R. D. Mckeown, R. Michaels, J. Niedziela, M. Olson, K. D. Pashke, G. A. Peterson, R. Pitthan, D. Relyea, S. E. Rock, O. Saxton, J. Singh, P. A. Souder, Z. M. Szalata, J. Turner, B. Tweedie, A. Vacharet, D. Walz, T. Weber, J. Weisend, M. Woods, I. Younus
Krishna Kumar
We report on a precision measurement of the parity-violating asymmetry in fixed target electron-electron (Møller) scattering: APV=[−131±14(stat)±10(syst)]×10−9, leading to the determination of the weak mixing angle sin2θeffW=0.2397±0.0010(stat)±0.0008(syst), evaluated at Q2=0.026 GeV2. Combining this result with the measurements of sin2θeffW at the Z0 pole, the running of the weak mixing angle is observed with over 6σ significance. The measurement sets constraints on new physics effects at the TeV scale.
The Average Shape Of Transport-Limited Aggregates, Benny Davidovitch, Jachyuk Choi, Martin Z. Bazant
The Average Shape Of Transport-Limited Aggregates, Benny Davidovitch, Jachyuk Choi, Martin Z. Bazant
Benny Davidovitch
We study the relation between stochastic and continuous transport-limited growth models, which generalize conformal-mapping formulations of diffusion-limited aggregation (DLA) and viscous fingering, respectively. We derive a nonlinear integro-differential equation for the asymptotic shape (average conformal map) of stochastic aggregates, whose mean-field approximation is the corresponding continuous equation, where the interface moves at its local expected velocity. Our equation accurately describes advection-diffusion-limited aggregation (ADLA), and, due to nonlinear averaging over fluctuations, the average ADLA cluster is similar, but not identical, to an exact solution of the mean-field dynamics. Similar results should apply to all models in our class, thus explaining the …
Pore Formation In Fluctuating Membranes, Oded Farago, Christian Santangelo
Pore Formation In Fluctuating Membranes, Oded Farago, Christian Santangelo
Christian Santangelo
We study the nucleation of a single pore in a fluctuating lipid membrane, specifically taking into account the membrane fluctuations, as well as the shape fluctuations of the pore. For large enough pores, the nucleationfree energy is well-described by shifts in the effective membrane surface tension and the pore line tension. Using our framework, we derive the stability criteria for the various pore formation regimes. In addition to the well-known large-tension regime from the classical nucleation theory of pores, we also find a low-tension regime in which the effective line and surface tensions can change sign from their bare values. …
Stark-Modulation Spectroscopy Of The B(1)[Π3] State Of Pbo, David Kawall, Y. V. Gurevich, C. Cheung, S. Bickman, Y. Jiang, D. Demille
Stark-Modulation Spectroscopy Of The B(1)[Π3] State Of Pbo, David Kawall, Y. V. Gurevich, C. Cheung, S. Bickman, Y. Jiang, D. Demille
David Kawall
We report detailed spectroscopic measurements of the X(0)[Σ+1](v=0)→B(1)[Π3](v=5) transition in PbO. Using a Stark-modulated laser absorption technique, we have measured the hyperfine constant of Pb207O in the B(1) state, as well as the B(1)(v=5) rotational constant, X−B isotope shifts, etc. The hyperfine constant of the B(1) state is of interest as a benchmark for calculations of PbO electronic structure related to experiments to search for the electric dipole moment of the electron.
Ground States And Thermal States Of The Random Field Ising Model, Yong Wu, Jonathan Machta
Ground States And Thermal States Of The Random Field Ising Model, Yong Wu, Jonathan Machta
Jonathan Machta
The random field Ising model is studied numerically at both zero and positive temperature. Ground states are mapped out in a region of random field and external field strength. Thermal states and thermodynamic properties are obtained for all temperatures using the Wang-Landau algorithm. The specific heat and susceptibility typically display sharp peaks in the critical region for large systems and strong disorder. These sharp peaks result from large domains flipping. For a given realization of disorder, ground states and thermal states near the critical line are found to be strongly correlated—a concrete manifestation of the zero temperature fixed point scenario.
Spreading Of Thin Films Assisted By Thermal Fluctuations, Benny Davidovitch, Esteban Moro, Howard A. Stone
Spreading Of Thin Films Assisted By Thermal Fluctuations, Benny Davidovitch, Esteban Moro, Howard A. Stone
Benny Davidovitch
We study the spreading of viscous drops on a solid substrate, taking into account the effects of thermal fluctuations in the fluid momentum. A nonlinear stochastic lubrication equation is derived, and studied using numerical simulations and scaling analysis. We show that asymptoically spreading drops admit self-similar shapes, whose average radii can increase at rates much faster than these predicted by Tanner's law. We discuss the physical realizablility of our results for thin molecular and complex fluid films, and predict that such phenomenon can in principal be observed in various flow geometries.
Anisotropic Spin Diffusion In Trapped Boltzmann Gases, Wj Mullin, Rj Ragan
Anisotropic Spin Diffusion In Trapped Boltzmann Gases, Wj Mullin, Rj Ragan
Physics Department Faculty Publication Series
Recent experiments in a mixture of two hyperfine states of trapped Bose gases show behavior analogous to a spin-1/2 system, including transverse spin waves and other familiar Leggett-Rice-type effects. We have derived the kinetic equations applicable to these systems, including the spin dependence of interparticle interactions in the collision integral, and have solved for spin-wave frequencies and longitudinal and transverse diffusion constants in the Boltzmann limit. We find that, while the transverse and longitudinal collision times for trapped Fermi gases are identical, the Bose gas shows diffusion anisotropy. Moreover, the lack of spin isotropy in the interactions leads to the …
Landau Damping Of Spin Waves In Trapped Boltzmann Gases, Rj Ragan, Wj Mullin, Eb Wiita
Landau Damping Of Spin Waves In Trapped Boltzmann Gases, Rj Ragan, Wj Mullin, Eb Wiita
Physics Department Faculty Publication Series
A semiclassical method is used to study Landau damping of transverse pseudo-spin waves in harmonically trapped ultracold gases in the collisionless Boltzmann limit. In this approach, the time evolution of a spin is calculated numerically as it travels in a classical orbit through a spatially dependent mean field. This method reproduces the Landau damping results for spin-waves in unbounded systems obtained with a dielectric formalism. In trapped systems, the simulations indicate that Landan damping occurs for a given spin-wave mode because of resonant phase space trajectories in which spins are "kicked out" of the mode (in spin space). A perturbative …
Vortex-Phonon Interaction, E Kozik, Boris Svistunov
Vortex-Phonon Interaction, E Kozik, Boris Svistunov
Physics Department Faculty Publication Series
Kelvin waves—helical waves on quantized vortex lines—are the normal modes of vortices in a superfluid. At zero temperature, the only dissipative channel of vortex dynamics is phonon emission. Starting with the hydrodynamic action, we derive the Hamiltonian of vortex-phonon interaction, thereby reducing the problem of the interaction of Kelvin waves with sound to inelastic elementary excitation scattering. On the basis of this formalism, we calculate the rate of sound radiation by superfluid turbulence at zero temperature and estimate the value of short-wavelength cutoff of the turbulence spectrum.
Absence Of Fragmentation In Two-Dimensional Bose-Einstein Condensation, Jp Fernandez, Wj Mullin
Absence Of Fragmentation In Two-Dimensional Bose-Einstein Condensation, Jp Fernandez, Wj Mullin
Physics Department Faculty Publication Series
We investigate the possibility that the BEC-like phenomena recently detected on two-dimensional finite trapped systems consist of fragmented condensates. We derive and diagonalize the one-body density matrix of a two-dimensional isotropically trapped Bose gas at finite temperature. For the ideal gas, the procedure reproduces the exact harmonic-oscillator eigenfunctions and the Bose distribution. We use a new collocation-minimization method to study the interacting gas in the Hartree-Fock approximation and obtain a ground-state wavefunction and condensate fraction consistent with those obtained by other methods. The populations of the next few eigenstates increase at the expense of the ground state but continue to …
Long Distance Effects And Strangeness In The Nucleon, John Donoghue, Barry Holstein, Tobias Huber, Andreas Ross
Long Distance Effects And Strangeness In The Nucleon, John Donoghue, Barry Holstein, Tobias Huber, Andreas Ross
Physics Department Faculty Publication Series
We discuss the calculation of the strange magnetic radius of the proton in chiral perturbation theory. In particular, we investigate the low-energy component of the loop integrals involving kaons. We separate the chiral calculation into a low-energy part and a high-energy component through use of a momentum space separation scale. This separation shows that most of the chiral calculation comes from high energies where the effective field theory treatment is not valid. The resulting low-energy prediction is in better agreement with dispersive treatments. Finally, we briefly discuss magnetic moments and show how our techniques can help resolve an old puzzle …