4,073 research outputs found
Correspondence principle in quantum gravity
The problem of consistent formulation of the correspondence principle in
quantum gravity is considered. The usual approach based on the use 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 this approach fails to describe whatever non-Newtonian
interactions of macroscopic bodies. An alternative interpretation of the
correspondence principle is given directly in terms of the effective action.
Gauge independence of the \hbar^0 part of the one-loop radiative corrections to
the gravitational form factors of the scalar particle is proved, justifying the
interpretation proposed. Application to the black holes is discussed.Comment: Talk presented at the international meeting "Quantum Gravity and
Spectral Geometry", Naples, July 2001. 4 pages, 1 figur
Quarkonium Decays and Light Quark Masses
The -violating decays \Phi^{2S} \goto \Phi^{1S} X, where
or and or have been recently proposed as a
means of probing the light quark masses beyond leading order in chiral
perturbation theory. We argue that this analysis is incorrect, even in the
heavy quark limit. We show that these decays are governed by an infinite number
of matrix elements which are not suppressed by any small parameter, and which
cannot be computed with our present understanding of QCD. Furthermore, for
sufficiently heavy quarks, we show that the decay amplitudes can be organized
into a twist expansion, and that the contributions considered in the above
proposal are subleading in this expansion. We also explain how these decays
nonetheless give a constraint on the light quark masses valid at {\it leading
order} in the chiral expansion. The decays \Phi^{1S} \goto \eta\gamma and
\Phi^{2S} \goto \Phi^{1S} \pi\pi also have contributions from infinitely many
operators, contrary to claims in the literature.Comment: 8 pages, LBL-33946, UCB-PTH-93/1
Quantum power correction to the Newton law
We have found the graviton contribution to the one-loop quantum correction to
the Newton law. This correction results in interaction decreasing with distance
as 1/r^3 and is dominated numerically by the graviton contribution. The
previous calculations of this contribution to the discussed effect are
demonstrated to be incorrect.Comment: 10 pages, 5 figures; numerical error corrected, few references adde
Effective Gravitational Field of Black Holes
The problem of interpretation of the \hbar^0-order part of radiative
corrections to the effective gravitational field is considered. It is shown
that variations of the Feynman parameter in gauge conditions fixing the general
covariance are equivalent to spacetime diffeomorphisms. This result is proved
for arbitrary gauge conditions at the one-loop order. It implies that the
gravitational radiative corrections of the order \hbar^0 to the spacetime
metric can be physically interpreted in a purely classical manner. As an
example, the effective gravitational field of a black hole is calculated in the
first post-Newtonian approximation, and the secular precession of a test
particle orbit in this field is determined.Comment: 8 pages, LaTeX, 1 eps figure. Proof of the theorem and typos
correcte
Systematics of soft final state interactions in decay
By using very general and well established features of soft strong
interactions we show, contrary to conventional expectations, that (i) soft
final state interactions (FSI) do not disappear for large , (ii) inelastic
rescattering is expected to be the main source of soft FSI phases, and (iii)
flavor off-diagonal FSI are suppressed by a power of , but are quite
likely to be significant at ~GeV. We briefly discuss the influence
of these interactions on tests of CP-violation and on theoretical calculations
of weak decays.Comment: 11 pages, REVTeX, no figure
Absorptive part of meson--baryon scattering amplitude and baryon polarization in chiral perturbation theory
We compute the spin asymmetry and polarization of the final-state baryon in
its rest frame in two-body meson--baryon low-energy scattering with unpolarized
initial state, to lowest non-trivial order in BChPT. The required absorptive
amplitudes are obtained analytically at one-loop level. We discuss the
polarization results numerically for several meson--baryon processes. Even at
low energies above threshold, where BChPT can reasonably be expected to be
applicable, sizable values of polarization are found for some processes
One loop calculations on the Wess-Zumino-Witten anomalous functional at finite temperature
We analyze the finite temperature (T) extension of the Wess-Zumino- Witten
functional, discussed in a previous work, to one loop in chiral perturbation
theory. As a phenomenological application, we calculate finite temperature
corrections to the amplitude of the decay into two photons. This
calculation is performed in three limits : i), ii)the chiral
limit at finite T and iii) ( being the pion mass). The
-corrections tend to vanish in the chiral limit, where only the kaon
contribution remains (although it is exponentially suppressed).Comment: Latex, 13 pages and 3 figures avalaible upon reques
On the power counting of loop diagrams in general relativity
A class of loop diagrams in general relativity appears to have a behavior
which would upset the utility of the energy expansion for quantum effects. We
show through the study of specific diagrams that cancellations occur which
restore the expected behaviour of the energy expansion. By considering the
power counting in a physical gauge we show that the apparent bad behavior is a
gauge artifact, and that the quantum loops enter with a well behaved energy
expansion.Comment: 29 pages, uses axodraw and epsfig.tex, one small .eps file is
included. The full PostScript version is also available as
http://het.phast.umass.edu/students/kakukk/powercount_hepth.p
Lifetime Differences in Heavy Mesons With Time Independent Measurements
Heavy meson pairs produced in the decays of heavy quarkonium resonances at e+
e- machines (beauty and tau-charm factories) have the useful property that the
two mesons are in the CP-correlated states. By tagging one of the mesons as a
CP eigenstate, a lifetime difference of heavy neutral meson mass eigenstates
width difference may be determined by measuring the leptonic branching ratio of
the other meson. We discuss the use of this and related methods both in the
case where time dependent mixing is small and when it is significant. We
consider the impact of possible CP-violating effects and present the complete
results for CP-entangled decay rates with CP-violation taken into account.Comment: 14 pages, 0 figures; 2 references added, results unchange
Final state rescattering as a contribution to
We provide a new estimate of the long-distance component to the radiative
transition . Our mechanism involves the soft-scattering of
on-shell hadronic products of nonleptonic decay, as in the chain . We employ a phenomenological fit to scattering data
to estimate the effect. The specific intermediate states considered here modify
the decay rate at roughly the level, although
the underlying effect has the potential to be larger. Contrary to other
mechanisms of long distance physics which have been discussed in the
literature, this yields a non-negligible modification of the channel and hence will provide an uncertainty in the extraction of
. This mechanism also affects the isospin relation between the rates
for and and may generate CP
asymmetries at experimentally observable levels.Comment: 15 pages, RevTex, 3 figure
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