801 research outputs found
Electrodynamics with radiation reaction
The self force of electrodynamics is derived from a scalar field. The
resulting equation of motion is free of all of the problems that plague the
Lorentz Abraham Dirac equation. The age-old problem of a particle in a constant
field is solved and the solution has intuitive appeal.Comment: 5 page
Using Nonlinear Response to Estimate the Strength of an Elastic Network
Disordered networks of fragile elastic elements have been proposed as a model
of inner porous regions of large bones [Gunaratne et.al., cond-mat/0009221,
http://xyz.lanl.gov]. It is shown that the ratio of responses of such
a network to static and periodic strain can be used to estimate its ultimate
(or breaking) stress. Since bone fracture in older adults results from the
weakening of porous bone, we discuss the possibility of using as a
non-invasive diagnostic of osteoporotic bone.Comment: 4 pages, 4 figure
Quantum general relativity and Hawking radiation
In a previous paper we have set up the Wheeler-DeWitt equation which
describes the quantum general relativistic collapse of a spherical dust cloud.
In the present paper we specialize this equation to the case of matter
perturbations around a black hole, and show that in the WKB approximation, the
wave-functional describes an eternal black hole in equilibrium with a thermal
bath at Hawking temperature.Comment: 13 pages, minor revisions in: (i) para 5 of Introduction, (ii) para
following Eqn. (10). Revised version to appear in Phys. Rev.
Analytical and numerical investigation of escape rate for a noise driven bath
We consider a system-reservoir model where the reservoir is modulated by an
external noise. Both the internal noise of the reservoir and the external noise
are stationary, Gaussian and are characterized by arbitrary decaying
correlation functions. Based on a relation between the dissipation of the
system and the response function of the reservoir driven by external noise we
numerically examine the model using a full bistable potential to show that one
can recover the turn-over features of the usual Kramers' dynamics when the
external noise modulates the reservoir rather than the system directly. We
derive the generalized Kramers' rate for this nonequilibrium open system. The
theoretical results are verified by numerical simulation.Comment: Revtex, 25 pages, 5 figures. To appear in Phys. Rev.
Conformal linear gravity in de Sitter space II
From the group theoretical point of view, it is proved that the theory of
linear conformal gravity should be written in terms of a tensor field of rank-3
and mixed symmetry [Binegar, et al, Phys. Rev. D 27, (1983) 2249]. We obtained
such a field equation in de Sitter space [Takook, et al, J. Math. Phys. 51,
(2010) 032503]. In this paper, a proper solution to this equation is obtained
as a product of a generalized polarization tensor and a massless scalar field
and then the conformally invariant two-point function is calculated. This
two-point function is de Sitter invariant and free of any pathological
large-distance behavior.Comment: 16 pages, no figure, published versio
Production and Decay of D_1(2420)^0 and D_2^*(2460)^0
We have investigated and final states and
observed the two established charmed mesons, the with mass
MeV/c and width MeV/c and
the with mass MeV/c and width
MeV/c. Properties of these final states, including
their decay angular distributions and spin-parity assignments, have been
studied. We identify these two mesons as the doublet predicted
by HQET. We also obtain constraints on {\footnotesize } as a function of the cosine of the relative phase of the two
amplitudes in the decay.Comment: 15 pages in REVTEX format. hardcopies with figures can be obtained by
sending mail to: [email protected]
First Observation of Coherent Production in Neutrino Nucleus Interactions with 2 GeV
The MiniBooNE experiment at Fermilab has amassed the largest sample to date
of s produced in neutral current (NC) neutrino-nucleus interactions at
low energy. This paper reports a measurement of the momentum distribution of
s produced in mineral oil (CH) and the first observation of coherent
production below 2 GeV. In the forward direction, the yield of events
observed above the expectation for resonant production is attributed primarily
to coherent production off carbon, but may also include a small contribution
from diffractive production on hydrogen. Integrated over the MiniBooNE neutrino
flux, the sum of the NC coherent and diffractive modes is found to be (19.5
1.1 (stat) 2.5 (sys))% of all exclusive NC production at
MiniBooNE. These measurements are of immediate utility because they quantify an
important background to MiniBooNE's search for
oscillations.Comment: Submitted to Phys. Lett.
The Kuiper Belt and Other Debris Disks
We discuss the current knowledge of the Solar system, focusing on bodies in
the outer regions, on the information they provide concerning Solar system
formation, and on the possible relationships that may exist between our system
and the debris disks of other stars. Beyond the domains of the Terrestrial and
giant planets, the comets in the Kuiper belt and the Oort cloud preserve some
of our most pristine materials. The Kuiper belt, in particular, is a
collisional dust source and a scientific bridge to the dusty "debris disks"
observed around many nearby main-sequence stars. Study of the Solar system
provides a level of detail that we cannot discern in the distant disks while
observations of the disks may help to set the Solar system in proper context.Comment: 50 pages, 25 Figures. To appear in conference proceedings book
"Astrophysics in the Next Decade
Study of the B^0 Semileptonic Decay Spectrum at the Upsilon(4S) Resonance
We have made a first measurement of the lepton momentum spectrum in a sample
of events enriched in neutral B's through a partial reconstruction of B0 -->
D*- l+ nu. This spectrum, measured with 2.38 fb**-1 of data collected at the
Upsilon(4S) resonance by the CLEO II detector, is compared directly to the
inclusive lepton spectrum from all Upsilon(4S) events in the same data set.
These two spectra are consistent with having the same shape above 1.5 GeV/c.
From the two spectra and two other CLEO measurements, we obtain the B0 and B+
semileptonic branching fractions, b0 and b+, their ratio, and the production
ratio f+-/f00 of B+ and B0 pairs at the Upsilon(4S). We report b+/b0=0.950
(+0.117-0.080) +- 0.091, b0 = (10.78 +- 0.60 +- 0.69)%, and b+ = (10.25 +- 0.57
+- 0.65)%. b+/b0 is equivalent to the ratio of charged to neutral B lifetimes,
tau+/tau0.Comment: 14 page, postscript file also available at
http://w4.lns.cornell.edu/public/CLN
Measurement of the branching fraction for
We have studied the leptonic decay of the resonance into tau
pairs using the CLEO II detector. A clean sample of tau pair events is
identified via events containing two charged particles where exactly one of the
particles is an identified electron. We find . The result is consistent with
expectations from lepton universality.Comment: 9 pages, RevTeX, two Postscript figures available upon request, CLNS
94/1297, CLEO 94-20 (submitted to Physics Letters B
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