5,045 research outputs found
Light-cone behavior of the pion Bethe-Salpeter wave function in the ladder model
The Bethe-Salpeter wave function χ(q^ν+P^ν, q^ν) for two spin-½ quarks bound by the exchange of a scalar meson is examined in the ladder model. We seek the behavior of χ as the squared momentum, (q+P)^2, on one leg becomes infinite while the squared momentum, q^2, on the other leg remains fixed. This behavior is investigated by making a Wick rotation, expanding χ in partial-wave amplitudes χ^i_J(q^2) of the group O(4), and then looking for the rightmost poles of χ^i_J(q^2) in the complex J plane. Our results verify (in the ladder model) the useful hypothesis that the locations of these poles are independent of q^2 and can thus be computed in the q^2→∞ limit by using conformal invariance
Large-Q^2 behavior of the pion electromagnetic form factor
We study the large-Q^2 behavior of the electromagnetic form factor of the pion, which is viewed as a quark-antiquark bound state in a (nongauge) quantum field theory. When the pion's Bethe-Salpeter wave function is expanded in O(4) partial waves, it is found that the information needed about the partial-wave amplitudes is their scaling behavior at large momentum and the locations of their poles in the complex J plane. This information is determined by using the operator-product expansion, conformal invariance at short distances, and a regularity property that holds at least in the ladder model. The resulting behavior of the form factor is roughly F(Q^2)~(Q^2)^(-1), with corrections due to anomalous dimensions
The American Religious Landscape and the 2004 Presidential Vote: Increased Polarization
Presents findings from a post-election survey conducted in November and December 2004. Explores the polarization between different religions, as well as within the major religious traditions
Origin of FRW cosmology in slow-roll inflation from noncompact Kaluza-Klein theory
Using a recently introduced formalism we discuss slow-roll inflaton from
Kaluza-Klein theory without the cylinder condition. In particular, some
examples corresponding to polynomic and hyperbolic -potentials are
studied. We find that the evolution of the fifth coordinate should be
determinant for both, the evolution of the early inflationary universe and the
quantum fluctuations.Comment: (final version) to be published in EPJ
Extra force and extra mass from noncompact Kaluza-Klein theory in a cosmological model
Using the Hamilton-Jacobi formalism, we study extra force and extra mass in a
recently introduced noncompact Kaluza-Klein cosmological model. We examine the
inertial 4D mass of the inflaton field on a 4D FRW bulk in two examples.
We find that has a geometrical origin and antigravitational effects on a
non inertial 4D bulk should be a consequence of the motion of the fifth
coordinate with respect to the 4D bulk.Comment: final version to be published in EPJ
Cosmological Surrealism: More than ``Eternal Reality" is Needed
Inflationary Cosmology makes the universe ``eternal" and provides for
recurrent universe creation, ad infinitum -- making it also plausible to assume
that ``our" Big Bang was also preceeded by others, etc.. However, GR tells us
that in the ``parent" universe's reference frame, the newborn universe's
expansion will never start. Our picture of ``reality" in spacetime has to be
enlarged.Comment: 7 pages, TAUP N23
Inflation without Slow Roll
We draw attention to the possibility that inflation (i.e. accelerated
expansion) might continue after the end of slow roll, during a period of fast
oscillations of the inflaton field \phi . This phenomenon takes place when a
mild non-convexity inequality is satisfied by the potential V(\phi). The
presence of such a period of \phi-oscillation-driven inflation can
substantially modify reheating scenarios.
In some models the effect of these fast oscillations might be imprinted on
the primordial perturbation spectrum at cosmological scales.Comment: 9 pages, Revtex, psfig, 1 figure, minor modifications, references
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The exact three-dimensional half-shell t-matrix for a sharply cut-off Coulomb potential in the screening limit
The three-dimensional half-shell t-matrix for a sharply cut-off Coulomb
potential is analytically derived together with its asymptotic form without
reference to partial wave expansion. The numerical solutions of the
three-dimensional Lippmann-Schwinger equation for increasing cut-off radii
provide half-shell t-matrices which are in quite a good agreement with the
asymptotic values.Comment: 15 pages, 4 eps figure
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