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Cosmology and the S-matrix

Description: We study conditions for the existence of asymptotic observables in cosmology. With the exception of de Sitter space, the thermal properties of accelerating universes permit arbitrarily long observations, and guarantee the production of accessible states of arbitrarily large entropy. This suggests that some asymptotic observables may exist, despite the presence of an event horizon. Comparison with decelerating universes shows surprising similarities: Neither type suffers from the limitations enc… more
Date: January 25, 2005
Creator: Bousso, Raphael
Partner: UNT Libraries Government Documents Department
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Pole-factorization theorem in quantum electrodynamics

Description: In quantum electrodynamics a classical part of the S-matrix is normally factored out in order to obtain a quantum remainder that can be treated perturbatively without the occurrence of infrared divergences. However, this separation, as usually performed, introduces spurious large-distance effects that produce an apparent breakdown of the important correspondence between stable particles and poles of the S-matrix, and, consequently, lead to apparent violations of the correspondence principle and… more
Date: January 1, 1996
Creator: Stapp, Henry P.
Partner: UNT Libraries Government Documents Department
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Measurement of the Wolfenstein Parameter R at 210 Mev.

Description: "Recent theoretical advances in describing the nucleon-nucleon interaction (particularly in the T=1 state) have emphasized the importance of obtaining an unambiguous experimental determination of the scattering matrix so that the nuclear phase shifts and details of the nuclear potential may be revealed. It is possible to select five experiments, the results of which, in principle at least, determine the scattering matrix and phase shifts uniquely at one energy. Two of these experiments, the cr… more
Date: August 1, 1960
Creator: Gibson, W. A.; England, A. C. (Alan Coulter), 1932-; Heer, E. & Tinlot, J. H.
Partner: UNT Libraries Government Documents Department
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Molecular Dynamics Simulations of Temperature Equilibration in Dense Hydrogen

Description: The temperature equilibration rate in dense hydrogen (for both T{sub i} > T{sub e} and T{sub i} < T{sub e}) has been calculated with large-scale molecular dynamics simulations for temperatures between 10 and 300 eV and densities between 10{sup 20}/cc to 10{sup 24}/cc. Careful attention has been devoted to convergence of the simulations, including the role of semiclassical potentials. We find that for Coulomb logarithms L {approx}> 1, Brown-Preston-Singleton [Brown et al., Phys. Rep. 41… more
Date: February 14, 2008
Creator: Glosli, J; Graziani, F; More, R; Murillo, M; Streitz, F; Surh, M et al.
Partner: UNT Libraries Government Documents Department
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The Proton-Proton Triple Scattering Parameters R and A at 213 Mev

Description: "As a part of a program to determine the p-p scattering matrix at 213 Mev, the triple scattering parameters R and A were measured at 30, 40, 50, 60, 70, 80. and 90 deg in the center-of-msss system. The results are compared with a phase shift analysis by MacGregor and Moravcsik and with the predictions of the boundary condition model of Saylor, Bryan and Marshak."
Date: April 17, 1961
Creator: England, Alan C.; Givson, William A. & Gotow, Kazuo
Partner: UNT Libraries Government Documents Department
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Phenomenology of light systems using R-matrix theory.

Description: Over the last 30 years, a program of R-matrix analyses has been carried out at Los Alamos in the mass range 2 {le} A {le} 18 that gives useful information about the light systems. These analyses provide data for astrophysics, as well as for neutronic and thermonuclear applications, and can yield important constraints from the experimental measurements on the nature of few-body interactions. Following a brief introduction to R-matrix theory, I will describe recent work on reactions in the A=2 (N… more
Date: January 1, 2001
Creator: Hale, G. M. (Gerald M.)
Partner: UNT Libraries Government Documents Department
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PROPERTIES OP LIQUID HELIUM-THREE IN THE TWO-BODY CORRELATION APPROXIMATION. I

Description: This is the first of two papers in which the low-temperature properties of liquid He{sup 3} are to be calculated in the thermodynamically consistent 'T-matrix' approximation. The set of coupled integral equations which are to be solved is exhibited in Part A of this paper. Part B of this paper is devoted to a preliminary, zero-temperature calculation which employs the additional approximations of using separable potentials and a noninteracting spectral function to define the interaction of two … more
Date: November 17, 1965
Creator: Beck, Donald E. & Sessler, Andrew M.
Partner: UNT Libraries Government Documents Department
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Final state interaction phase in B decays

Description: From an estimate of the meson-meson inelastic scattering at 5 GeV it is concluded that a typical strong phase in B decays to two mesons is of order of 20{sup o}. For a particular final state an estimate of the phase depends on whether that state is more or less probable as a final state compared to those states to which it is connected by the strong interaction S matrix.
Date: March 24, 1999
Creator: Suzuki, Mahiko & Wolfenstein, Lincoln
Partner: UNT Libraries Government Documents Department
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Probing the nonlocal approximation to resonant collisions ofelectrons with diatomic molecules

Description: A numerically solvable two-dimensional model introduced bythe authors [Phys. Rev. A 73, 032721 (2006)]is used to investigate thevalidity of the nonlocal approximation to the dynamics of resonantcollisions of electrons with diatomic molecules. The nonlocalapproximation to this model is derived in detail, all underlyingassumptions are specified and explicit expressions for the resonant andnon-resonant (background) T matrix for the studied processes are given.Different choices of the so-called dis… more
Date: September 7, 2007
Creator: Houfek, Karel; Rescigno, Thomas N. & McCurdy, C. William
Partner: UNT Libraries Government Documents Department
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S-matrix Calculations of Energy Levels of the Lithium Isoelectronic Sequence

Description: A QED approach to the calculation of the spectra of the lithium isoelectronic sequence is implemented. A modified Furry representation based on the Kohn-Sham potential is used to evaluate all one- and two-photon diagrams with the exception of the two-loop Lamb shift. Three-photon diagrams are estimated with Hamiltonian methods. After incorporating recent calculations of the two-loop Lamb shift and recoil corrections a comprehensive tabulation of the 2s, 2p{sub 1/2} and 2p{sub 3/2} energy levels… more
Date: November 2, 2010
Creator: sapirstein, J & Cheng, K T
Partner: UNT Libraries Government Documents Department
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Two-dimensional resonances in Coulomb few body system and theory of electron energy and angular distribution

Description: The two-dimensional resonances in the problem of two Coulomb centers are discussed. The ab initio calculation of electron energy and angular distributions of saddle-point and S-promotion electrons for ionization in proton-hydrogen atom collisions are presented. The calculation is based on an outgoing wave Sturmian expansion in the frequency domain. It goes beyond the usual Born-Oppenheimer separation of electron and nuclei motions and displays the ``{upsilon}/2`` peak and the continuum cusp, mi… more
Date: December 31, 1994
Creator: Ovchinnikov, S.Y. & Macek, J.H.
Partner: UNT Libraries Government Documents Department
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New relativistic S-matrix results for scattering -- beyond the usual anomalous factors/beyond impulse approximation

Description: The relativistic second-order S-matrix elements for photon-atom scattering have been successfully calculated with numerical methods within the independent particle approximation (IPA). This permits an assessment of the validity of simpler approximate predictions which are commonly used and it offers the possibility of improved tabulations of theoretical predictions. A variety of unresolved issues remain, some associated with the relativistic theory, some with IPA. The systematic use of the seco… more
Date: August 1, 1993
Creator: Pratt, R. H.; Bergstrom, P. M. Jr. & Kissel, L.
Partner: UNT Libraries Government Documents Department
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Elastic and transition form factors of mesons

Description: The Dyson-Schwinger equations [DSEs] provide a Poincare invariant, non-perturbative, renormalisable, continuum approach to solving gauge field theories, which also yields perturbation theory in the weak coupling limit. The elementary quantities in this approach are the Schwinger functions, which are the moments of the measure of the field theory. their analytic properties provide information about confinement and dynamical chiral symmetry breaking two-point quark and gluon Schwinger functions i… more
Date: July 1, 1996
Creator: Roberts, C.D.
Partner: UNT Libraries Government Documents Department
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Toward improved photon-atom scattering predictions

Description: Photon-atom scattering is important in a variety of applications, but scattering from a composite system depends on the accurate characterization of the scattering from an isolated atom or ion. We have been examining the validity of simpler approximations of elastic scattering in the light of second-order S-matrix theory. Partitioning the many-body amplitude into Rayleigh and Delbrueck components, processes beyond photoionization contribute. Subtracted cross sections for bound-bound atomic tran… more
Date: October 21, 1994
Creator: Kissel, L.
Partner: UNT Libraries Government Documents Department
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