1,544 research outputs found
Radiation Information from 1958 δ2
The telemetered radiation information from the satellite 1958 δ2
(Sputnik III) has been analyzed for sixty-two separate passes recorded
in College, Alaska. The data indicate a dependence of radiation intensity
on altitude in the range 250-500 km. Both the high and low
energy components apparently contribute to the overall increase of
intensity with altitude, but the presence of a continuous afterglow
in the scintillating crystal prevented detailed interpretation of the
results.IGY Project No. 32.42
NSF Grant No. Y/32.42/268Ye
Representations of Spacetime Alternatives and Their Classical Limits
Different quantum mechanical operators can correspond to the same classical
quantity. Hermitian operators differing only by operator ordering of the
canonical coordinates and momenta at one moment of time are the most familiar
example. Classical spacetime alternatives that extend over time can also be
represented by different quantum operators. For example, operators representing
a particular value of the time average of a dynamical variable can be
constructed in two ways: First, as the projection onto the value of the time
averaged Heisenberg picture operator for the dynamical variable. Second, as the
class operator defined by a sum over those histories of the dynamical variable
that have the specified time-averaged value. We show both by explicit example
and general argument that the predictions of these different representations
agree in the classical limit and that sets of histories represented by them
decohere in that limit.Comment: 11 pages, 10 figures, Revtex4, minor correction
Fourier Transforms of Lorentz Invariant Functions
Fourier transforms of Lorentz invariant functions in Minkowski space, with
support on both the timelike and the spacelike domains are performed by means
of direct integration. The cases of 1+1 and 1+2 dimensions are worked out in
detail, and the results for 1+n dimensions are given.Comment: 15 pages, 1 figur
The Fermion Self-Energy during Inflation
We compute the one loop fermion self-energy for massless Dirac + Einstein in
the presence of a locally de Sitter background. We employ dimensional
regularization and obtain a fully renormalized result by absorbing all
divergences with BPHZ counterterms. An interesting technical aspect of this
computation is the need for a noninvariant counterterm owing to the breaking of
de Sitter invariance by our gauge condition. Our result can be used in the
quantum-corrected Dirac equation to search for inflation-enhanced quantum
effects from gravitons, analogous to those which have been found for massless,
minimally coupled scalars.Comment: 63 pages, 3 figures (uses axodraw.sty), LaTeX 2epsilon. Revised
version (to appear in Classical and Quantum Gravity) corrects some typoes and
contains some new reference
Decoherence Functional and Probability Interpretation
We confirm that the diagonal elements of the Gell-Mann and Hartle's
decoherence decoherence functional are equal to the relative frequencies of the
results of many identical experiments, when a set of alternative histories
decoheres. We consider both cases of the pure and mixed initial states.Comment: 9 pages, UCSBTH-92-40 and MMC-M-
Cosmological implications of conformal field theory
Requiring all massless elementary fields to have conformal scaling symmetry
removes a conflict between gravitational theory and the quantum theory of
elementary particles and fields. Extending this postulate to the scalar field
of the Higgs model, dynamical breaking of both gauge and conformal symmetries
determines parameters for the interacting fields. In uniform isotropic geometry
a modified Friedmann cosmic evolution equation is derived with nonvanishing
cosmological constant. Parameters determined by numerical solution are
consistent with empirical data for redshifts , including
luminosity distances for observed type Ia supernovae and peak structure ratios
in the cosmic microwave background (CMB). The theory does not require dark
matter.Comment: 8 pages Conclusions about the early universe which must be reexamined
have been removed. Manuscript revised and reformatted. Accepted for
publication in Modern Physics Letters A (2011
Considerations on the Unruh Effect: Causality and Regularization
This article is motivated by the observation, that calculations of the Unruh
effect based on idealized particle detectors are usually made in a way that
involves integrations along the {\em entire} detector trajectory up to the
infinitely remote {\em future}. We derive an expression which allows
time-dependence of the detector response in the case of a non-stationary
trajectory and conforms more explicitely to the principle of causality, namely
that the response at a given instant of time depends only on the detectors {\em
past} movements. On trying to reproduce the thermal Unruh spectrum we are led
to an unphysical result, which we trace down to the use of the standard
regularization t\to t-i\eps of the correlation function. By consistently
employing a rigid detector of finite extension, we are led to a different
regularization which works fine with our causal response function.Comment: 19 pages, 2 figures, v2: some minor change
Heat kernel of non-minimal gauge field kinetic operators on Moyal plane
We generalize the Endo formula originally developed for the computation of
the heat kernel asymptotic expansion for non-minimal operators in commutative
gauge theories to the noncommutative case. In this way, the first three
non-zero heat trace coefficients of the non-minimal U(N) gauge field kinetic
operator on the Moyal plane taken in an arbitrary background are calculated. We
show that the non-planar part of the heat trace asymptotics is determined by
U(1) sector of the gauge model. The non-planar or mixed heat kernel
coefficients are shown to be gauge-fixing dependent in any dimension of
space-time. In the case of the degenerate deformation parameter the lowest
mixed coefficients in the heat expansion produce non-local gauge-fixing
dependent singularities of the one-loop effective action that destroy the
renormalizability of the U(N) model at one-loop level. The twisted-gauge
transformation approach is discussed.Comment: 21 pages, misprints correcte
Factorization of gravitational Compton scattering amplitude in the linearized version of general relativity
Gravitational Compton scattering process with a massive fermion is studied in
the context of the linearized gravity. Gravitational gauge invariance and
graviton transversality cause the transition amplitude to be factorized into
that of scalar QED Compton scattering and that of fermion QED Compton
scattering with an overall kinematical factor. The factorization is shown
explicitly and its physical implications are discussed.Comment: 11 pages, 1 figure(not included), Revtex 3.0, SNUTP 93-2
Measurement Analysis and Quantum Gravity
We consider the question of whether consistency arguments based on
measurement theory show that the gravitational field must be quantized.
Motivated by the argument of Eppley and Hannah, we apply a DeWitt-type
measurement analysis to a coupled system that consists of a gravitational wave
interacting with a mass cube. We also review the arguments of Eppley and Hannah
and of DeWitt, and investigate a second model in which a gravitational wave
interacts with a quantized scalar field. We argue that one cannot conclude from
the existing gedanken experiments that gravity has to be quantized. Despite the
many physical arguments which speak in favor of a quantum theory of gravity, it
appears that the justification for such a theory must be based on empirical
tests and does not follow from logical arguments alone.Comment: 31 pages, many conceptual clarifications included, new appendix
added, to appear in Phys. Rev.
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