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Full-Text Articles in Physical Sciences and Mathematics
U-Duality, D-Branes And Black Hole Emission Rates: Agreements And Disagreements, Fay Dowker, David Kastor, Jennie Traschen
U-Duality, D-Branes And Black Hole Emission Rates: Agreements And Disagreements, Fay Dowker, David Kastor, Jennie Traschen
David Kastor
An expression for the spacetime absorption coefficient of a scalar field in a five dimensional, near extremal black hole background is derived, which has the same form as that presented by Maldacena and Strominger, but is valid over a larger, U-duality invariant region of parameter space and in general disagrees with the corresponding D-brane result. We develop an argument, based on D-brane thermodynamics, which specifies the range of parameters over which agreement should be expected. For neutral emission, the spacetime and D-brane results agree over this range. However, for charged emission, we find disagreement in the `Fat Black Hole' regime, …
Investigation Of The 10b(Γ,P) Reaction Using Tagged Photons, L J. De Bever, R S. Hicks, R A. Miskimen, Gerald Alvin Peterson
Investigation Of The 10b(Γ,P) Reaction Using Tagged Photons, L J. De Bever, R S. Hicks, R A. Miskimen, Gerald Alvin Peterson
Gerald Alvin Peterson
The reaction 10B(γ,p) has been studied using tagged photons of mean energies Eγ=57.6 and 72.9 MeV. Angular distributions and derived single-particle momentum distributions for protons leading to the ground state of 9Be and higher excited states are compared to various calculations made using model parameters constrained by 10B(e,e′p)9Be and 9Be(p,p′)9Be measurements. The effects of varying final-state interactions (including channel couplings) and meson exchange currents are considered. A sizable discrepancy between direct-knockout calculations and the experimental results is observed. If meson exchange currents are included in an approximate fashion, a good description of the 10B(γ,p0)9Be data is found.
Quantum-Monte-Carlo Calculations For Bosons In A Two-Dimensional Harmonic Trap, Stefan Heinrichs, William J. Mullin
Quantum-Monte-Carlo Calculations For Bosons In A Two-Dimensional Harmonic Trap, Stefan Heinrichs, William J. Mullin
Physics Department Faculty Publication Series
Path-Integral-Monte-Carlo simulation has been used to calculate the properties of a two-dimensional (2D) interacting Bose system. The bosons interact with hard-core potentials and are confined to a harmonic trap. Results for the density profiles, the condensate fraction, and the superfluid density are presented. By comparing with the ideal gas we easily observe the effects of finite size and the depletion of the condensate because of interactions. The system is known to have no phase transition to a Bose-Einstein condensation in 2D, but the finite system shows that a significant fraction of the particles are in the lowest state at low …
Measurements Of The Δ(1232) Transition Form Factor And The Ratio Σn/Σp From Inelastic Electron-Proton And Electron-Deuteron Scattering, L M. Stuart, R S. Hicks, R A. Miskimen, Gerald Alvin Peterson, S H. Rokni
Measurements Of The Δ(1232) Transition Form Factor And The Ratio Σn/Σp From Inelastic Electron-Proton And Electron-Deuteron Scattering, L M. Stuart, R S. Hicks, R A. Miskimen, Gerald Alvin Peterson, S H. Rokni
Gerald Alvin Peterson
Measurements of inclusive electron-scattering cross sections using hydrogen and deuterium targets in the region of the Δ(1232) resonance are reported. A global fit to these new data and previous data in the resonance region is also reported for the proton. Transition form factors have been extracted from the proton cross sections for this experiment over the four-momentum transfer squared range 1.64
Radial Dependence Of The Nucleon Effective Mass In 10b, L J. De Bever, R S. Hicks, R A. Miskimen, Gerald Alvin Peterson
Radial Dependence Of The Nucleon Effective Mass In 10b, L J. De Bever, R S. Hicks, R A. Miskimen, Gerald Alvin Peterson
Gerald Alvin Peterson
The dynamic properties of the atomic nucleus depend strongly on correlations between the nucleons. We present a combined analysis of inelastic electron-scattering data and electron-induced proton knockout measurements in an effort to obtain phenomenological information on nucleon-nucleon correlations. Our results indicate that the ratio of radial wave functions extracted from precise 10B(e,e′) and 10B(e,e′p) measurements evolve from an interior depression for small Em, characteristic of short-range correlations, to a surface-peaked enhancement for larger Em, characteristic of long-range correlations. This observation can be interpreted in terms of the nucleon effective mass.
Brownian Motion And Polymer Statistics On Certain Curved Manifolds, Radu P. Mondescu, M. Muthukumar
Brownian Motion And Polymer Statistics On Certain Curved Manifolds, Radu P. Mondescu, M. Muthukumar
Physics Department Faculty Publication Series
No abstract provided.
Exact, Complete, And Universal Continuous-Time Worldline Monte Carlo Approach To The Statistics Of Discrete Quantum Systems, Nikolai Prokof'ev, Boris Svistunov, Tupitsyn
Exact, Complete, And Universal Continuous-Time Worldline Monte Carlo Approach To The Statistics Of Discrete Quantum Systems, Nikolai Prokof'ev, Boris Svistunov, Tupitsyn
Physics Department Faculty Publication Series
We show how the worldline quantum Monte Carlo procedure, which usually relies on an artificial time discretization, can be formulated directly in continuous time, rendering the scheme exact. For an arbitrary system with discrete Hilbert space, none of the configuration update procedures contain small parameters. We find that the most effective update strategy involves the motion of worldline discontinuities (both in space and time), i.e., the evaluation of the Green’s function. Being based on local updates only, our method nevertheless allows one to work with the grand canonical ensemble and nonzero winding numbers, and to calculate any dynamical correlation function …
U Duality, D-Branes, And Black Hole Emission Rates: Agreements And Disagreements, F Dowker, David Kastor, Jennie Traschen
U Duality, D-Branes, And Black Hole Emission Rates: Agreements And Disagreements, F Dowker, David Kastor, Jennie Traschen
Physics Department Faculty Publication Series
An expression for the spacetime absorption coefficient of a scalar field in a five-dimensional, near-extremal black hole background is derived, which has the same form as that presented by Maldacena and Strominger, but is valid over a larger, U-duality invariant region of parameter space and in general disagrees with the corresponding D-brane result. We develop an argument, based on D-brane thermodynamics, which specifies the range of parameters over which agreement should be expected. For neutral emission, the spacetime and D-brane results agree over this range. However, for charged emission, we find disagreement in the “fat black hole” regime, in which …
Non-Extreme Calabi-Yau Black Holes, David Kastor, K.Z Win
Non-Extreme Calabi-Yau Black Holes, David Kastor, K.Z Win
Physics Department Faculty Publication Series
Non-extreme black hole solutions of four dimensional, N = 2 supergravity theories with Calabi-Yau prepotentials are presented, which generalize certain known double-extreme and extreme solutions. The boost parameters characterizing the nonextreme solutions must satisfy certain constraints, which effectively limit the functional independence of the moduli scalars. A necessary condition for being able to take certain boost parameters independent is found to be block diagonality of the gauge coupling matrix. We present a number of examples aimed at developing an understanding of this situation and speculate about the existence of more general solutions.
A Study Of Bose-Einstein Condensation In A Two-Dimensional Trapped Gas, Wj Mullin
A Study Of Bose-Einstein Condensation In A Two-Dimensional Trapped Gas, Wj Mullin
Physics Department Faculty Publication Series
We examine the possibility of Bose-Einstein condensation (BEC) in two-dimensional (2D) system of interacting particles in a trap. We use a self-consistent mean-field theory of Bose particles interacting by a contact interaction in the Popov and WKB approximations. The equations show that the normal state has a phase transition at some critical temperature T c but below T c the Bose-Einstein condensed state is not a consistent solution of the equations in the thermodynamic limit. This result agrees with a theorem recently discussed by the author that shows that a BEC state is impossible for an interacting gas in a …
Chiral Anomaly And Eta-Eta ' Mixing, Ep Venugopal, Br Holstein
Chiral Anomaly And Eta-Eta ' Mixing, Ep Venugopal, Br Holstein
Physics Department Faculty Publication Series
We determine the η-η′ mixing angle via a procedure relatively independent of theoretical assumptions by simultaneously fitting η,η′ reactions involving the anomaly η,η′→γγ, π+π-γ. We extract reasonably precise renormalized values of the octet and singlet pseudoscalar decay constants F8, F0, as well as the mixing angle θ.
Compton Scattering And The Spin Structure Of The Nucleon At Low Energies, Tr Hemmert, Br Holstein, J Kambor, G Knochlein
Compton Scattering And The Spin Structure Of The Nucleon At Low Energies, Tr Hemmert, Br Holstein, J Kambor, G Knochlein
Physics Department Faculty Publication Series
We analyze polarized Compton scattering which provides information on the spin-structure of the nucleon. For scattering processes with photon energies up to 100 MeV the spin-structure dependence can be encoded into four independent parameters—the so-called spin-polarizabilities γi, i=1,…,4, of the nucleon, which we calculate within the framework of the “small scale expansion” in SU(2) baryon chiral perturbation theory. Specific application is made to “forward” and “backward” spin-polarizabilities.
Improved Treatment Of Loop Diagrams In Su(3) Baryon Chiral Perturbation Theory, Jf Donoghue, Br Holstein
Improved Treatment Of Loop Diagrams In Su(3) Baryon Chiral Perturbation Theory, Jf Donoghue, Br Holstein
Physics Department Faculty Publication Series
Baryon chiral perturbation theory as conventionally applied has a well-known problem with the SU(3) chiral expansion in that loop diagrams generate very large SU(3) breaking corrections and greatly upset the subsequent phenomenology. We argue that the problem comes from the portions of loop integrals corresponding to propagation at such short distances that the effective theory is not valid. One can reformulate the theory equally rigorously by regulating the loop integrals using a momentum-space cutoff which removes the spurious short-distance physics. We show that this reformulation improves the phenomenology for reasonable values of the cutoff.
Weight For Random Quark Masses, Jf Donoghue
Weight For Random Quark Masses, Jf Donoghue
Physics Department Faculty Publication Series
In theories in which the parameters of the low energy theory are not unique, perhaps having different values in different domains of the universe as is possible in some inflationary models, the fermion masses would be distributed with respect to some weight. In such a situation the specifics of the fermion masses do not have a unique explanation, yet the weight provides the visible remnant of the structure of the underlying theory. This paper introduces this concept of a weight for the distribution of masses and provides a quantitative estimate of it from the observed quarks and leptons. The weight …
Very Effective String Model?, David Kastor, Jennie Traschen
Very Effective String Model?, David Kastor, Jennie Traschen
Physics Department Faculty Publication Series
Additional evidence is presented for a recently proposed effective string model, conjectured to hold throughout the parameter space of the basic 5 dimensional, triply charged black holes, which includes the effects of brane excitations, as well as momentum modes. We compute the low energy spacetime absorption coefficient σ for the scattering of a triply charged scalar field in the near extremal case, and conjecture an exact form for σ. It is shown that this form of σ arises simply from the effective string model. This agreement encompasses both statistical factors coming from the Bose distributions of string excitations and a …