1,796 research outputs found
Baryon Masses in Chiral Perturbation Theory with Infrared Regularization
The baryon masses are examined in SU(3) chiral perturbation theory to third
order using the recently proposed infrared regularization scheme. Fourth order
is estimated by evaluating the dominant diagram. With this regularization the
magnitude of the loop integrals is reduced so that the convergence of the
series appears to be better than in the heavy baryon approach.Comment: The original third order calculation is supplemented by an estimate
of fourth order using just the dominant diagram. The convergence still
appears to be better than in the heavy baryon approach. To be published in
Phys. Rev. C. 15 pages latex, 2 postscript figure
On the correspondence between the classical and quantum gravity
The relationship between the classical and quantum theories of gravity is
reexamined. The value of the gravitational potential defined with the help of
the two-particle scattering amplitudes is shown to be in disagreement with the
classical result of General Relativity given by the Schwarzschild solution. It
is shown also that the potential so defined fails to describe whatever
non-Newtonian interactions of macroscopic bodies. An alternative interpretation
of the -order part of the loop corrections is given directly in terms
of the effective action. Gauge independence of that part of the one-loop
radiative corrections to the gravitational form factors of the scalar particle
is proved, justifying the interpretation proposed.Comment: Latex 2.09, 3 ps. figures, 17 page
On the Ultraviolet Behaviour of Newton's constant
We clarify a point concerning the ultraviolet behaviour of the Quantum Field
Theory of gravity, under the assumption of the existence of an ultraviolet
Fixed Point. We explain why Newton's constant should to scale like the inverse
of the square of the cutoff, even though it is technically inessential. As a
consequence of this behaviour, the existence of an UV Fixed Point would seem to
imply that gravity has a built-in UV cutoff when described in Planck units, but
not necessarily in other units.Comment: 8 pages; CQG class; minor changes and rearrangement
The Electromagnetic Mass Differences of Pions and Kaons
We use the Cottingham method to calculate the pion and kaon electromagnetic
mass differences with as few model dependent inputs as possible. The
constraints of chiral symmetry at low energy, QCD at high energy and
experimental data in between are used in the dispersion relation. We find
excellent agreement with experiment for the pion mass difference. The kaon mass
difference exhibits a strong violation of the lowest order prediction of
Dashen's theorem, in qualitative agreement with several other recent
calculations.Comment: 40 pages, Latex, needs axodraw. and psfig. macros, 4 figure
The Quantum Gravitationally Induced Stress Tensor
We derive non-perturbative relations between the expectation value of the
invariant element in a homogeneous and isotropic state and the quantum
gravitationally induced pressure and energy density. By exploiting previously
obtained bounds for the maximum possible growth of perturbative corrections to
a locally de Sitter background we show that the two loop result dominates all
higher orders. We also show that the quantum gravitational slowing of inflation
becomes non-perturbatively strong earlier than previously expected.Comment: 13 pages, LaTeX 2 epsilo
The Mixed Vector Current Correlator <0|T(V^3_\mu V^8_\nu )|0> To Two Loops in Chiral Perturbation Theory
The isospin-breaking correlator of the product of flavor octet vector
currents, and , is computed to
next-to-next- to-leading (two-loop) order in Chiral Perturbation Theory. Large
corrections to both the magnitude and -dependence of the one-loop result
are found, and the reasons for the slow convergence of the chiral series for
the correlator given. The two-loop expression involves a single
counterterm, present also in the two-loop expressions for
and , which counterterm
contributes a constant to the scalar correlator . The
feasibility of extracting the value of this counterterm from other sources is
discussed. Analysis of the slope of the correlator with respect to using
QCD sum rules is shown to suggest that, even to two-loop order, the chiral
series for the correlator may not yet be well-converged.Comment: 32 pages, uses REVTEX and epsfig.sty with 7 uuencoded figures. Entire
manuscript available as a ps file at
http://www.physics.adelaide.edu.au/theory/home.html Also available via
anonymous ftp at ftp://adelphi.adelaide.edu.au/pub/theory/ADP-95-27.T181.p
A global fit of and elastic scattering in ChPT with dispersion relations
We apply the one-loop results of the ChPT suplemented
with the inverse amplitude method to fit the available experimental data on
and scattering. With esentially only three parameters we
describe accurately data corresponding to six different channels, namely
and . In addition we
reproduce the first resonances of the and channel with the
right mass corresponding to the and the particles.Comment: 19 pages, 5 figures available on request, FT/UCM/10/9
Semiclassical limit for Dirac particles interacting with a gravitational field
The behavior of spin-1/2 particle in a weak static gravitational field is
considered. The Dirac Hamiltonian is diagonalized by the Foldy-Wouthuysen
transformation providing also the simple form for the momentum and spin
polarization operators. The operator equations of momentum and spin motion are
derived for a first time. Their semiclassical limit is analyzed. The dipole
spin-gravity coupling in the previously found (another) Hamiltonian does not
lead to any observable effects. The general agreement between the quantum and
classical analysis is established, contrary to several recent claims. The
expression for gravitational Stern-Gerlach force is derived. The helicity
evolution in the gravitational field and corresponding accelerated frame
coincides, being the manifestation of the equivalence principle.Comment: 8 pages, no figures; version to appear in Physical Review
One Loop Back Reaction On Chaotic Inflation
We extend, for the case of a general scalar potential, the inflaton-graviton
Feynman rules recently developed by Iliopoulos {\it et al.} As an application
we compute the leading term, for late co-moving times, of the one loop back
reaction on the expansion rate for . This is
expressed as the logarithmic time derivative of the scale factor in the
coordinate system for which the expectation value of the metric has the form:
. This quantity should be a gauge
independent observable. Our result for it agrees exactly with that inferred
from the effect previously computed by Mukhanov {\it et al.} using canonical
quantization. It is significant that the two calculations were made with
completely different schemes for fixing the gauge, and that our computation was
done using the standard formalism of covariant quantization. This should settle
some of the issues recently raised by Unruh.Comment: 41 pages, LaTeX 2 epsilo
Dispersive contribution to CP violation in hyperon decays
Within the standard model, CP-violating asymmetries A(\Lambda^0_-) and
A(\Xi^-_-) have been estimated in short-distance calculations to occur at the
level of a few times 10^{-5}. We show here that in this model the dispersive
contribution tends to give asymmetries of similar size.Comment: 10 pages, LaTe
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