819 research outputs found
The historical origins of the American Peace Test
This thesis explains the historical origins of the anti-nuclear protest group, the American Peace Test (APT), which has focused its activities at the Nevada Test Site. This study concludes that interest in direct action was evident during the 1983-1984 Direct Action Framework Period within the Nuclear Weapons FREEZE Campaign. This interest became more tangible with a call to the Nevada Desert Experience (NDE) group in May of 1985 requesting to participate in an action. That interest was then amplified and validated at that August NDE action. The first APT action was then organized for October and November. At the Annual FREEZE Conference, within the momentum of the October action, those interested decided to form their own group. Official formation occurred in January of 1986. The concluding chapter contains a summary of themes found in these origins and information relative to post-formation APT
The Symmetries of Nature
The study of the symmetries of nature has fascinated scientists for eons. The application of the formal mathematical description of
symmetries during the last century has produced many breakthroughs in
our understanding of the substructure of matter. In this talk, a number
of these advances are discussed, and the important role that George
Sudarshan played in their development is emphasize
Thermodynamical Laws in Horava-Lifshitz Gravity
In this work, we have investigated the validity of GSL of thermodynamics in a
universe (open, closed and flat) governed by Hoava-Lifshitz
gravity. If the universe contains barotropic fluid the corresponding solutions
have been obtained. The validity of GSL have been examined by two approaches:
(i) robust approach and (ii) effective approach. In robust approach, we have
considered the universe contains only matter fluid and the effect of the
gravitational sector of HL gravity was incorporated through the modified black
hole entropy on the horizon. Effective approach is that all extra information
of HL gravity into an effective dark energy fluid and so we consider the
universe contains matter fluid plus this effective fluid. This approach is
essentially same as the Einstein's gravity theory. The general prescription for
validity of GSL have been discussed. Graphically we have shown that the GSL may
be satisfied for open, closed and flat universe on the different horizons with
different conditions.Comment: 7 latex pages, 7 figure
Classical Limit of Demagnetization in a Field Gradient
We calculate the rate of decrease of the expectation value of the transverse
component of spin for spin-1/2 particles in a magnetic field with a spatial
gradient, to determine the conditions under which a previous classical
description is valid. A density matrix treatment is required for two reasons.
The first arises because the particles initially are not in a pure state due to
thermal motion. The second reason is that each particle interacts with the
magnetic field and the other particles, with the latter taken to be via a
2-body central force. The equations for the 1-body Wigner distribution
functions are written in a general manner, and the places where quantum
mechanical effects can play a role are identified. One that may not have been
considered previously concerns the momentum associated with the magnetic field
gradient, which is proportional to the time integral of the gradient. Its
relative magnitude compared with the important momenta in the problem is a
significant parameter, and if their ratio is not small some non-classical
effects contribute to the solution.
Assuming the field gradient is sufficiently small, and a number of other
inequalities are satisfied involving the mean wavelength, range of the force,
and the mean separation between particles, we solve the integro- partial
differential equations for the Wigner functions to second order in the strength
of the gradient. When the same reasoning is applied to a different problem with
no field gradient, but having instead a gradient to the z-component of
polarization, the connection with the diffusion coefficient is established, and
we find agreement with the classical result for the rate of decrease of the
transverse component of magnetization.Comment: 22 pages, no figure
A note on Friedmann equation of FRW universe in deformed Horava-Lifshitz gravity from entropic force
With entropic interpretation of gravity proposed by Verlinde, we obtain the
Friedmann equation of the Friedmann-Robertson-Walker universe for the deformed
Ho\v{r}ava-Lifshitz gravity. It is shown that, when the parameter of
Ho\v{r}ava-Lifshitz gravity , the modified Friedmann
equation will go back to the one in Einstein gravity. This results may imply
that the entropic interpretation of gravity is effective for the deformed
Ho\v{r}ava-Lifshitz gravity.Comment: 9 pages, no figure
Analyzing the Effects of Neutron Polarizabilities in Elastic Compton Scattering off He
Motivated by the fact that a polarized He nucleus behaves as an
`effective' neutron target, we examine manifestations of neutron
electromagnetic polarizabilities in elastic Compton scattering from the
Helium-3 nucleus. We calculate both unpolarized and double-polarization
observables using chiral perturbation theory to next-to-leading order
() at energies, , where is
the pion mass. Our results show that the unpolarized differential cross section
can be used to measure neutron electric and magnetic polarizabilities, while
two double-polarization observables are sensitive to different linear
combinations of the four neutron spin polarizabilities.
[Note added in 2018] The qualitative conclusions and analytic formulae
presented in this paper are correct, but several of the numerical results are
wrong: see the erratum posted as arXiv:1804.01206 for further details. A full
suite of corrected numerical results for cross sections and asymmetries can be
found in Margaryan et al., arXiv:1804.00956. They can also be obtained as an
interactive Mathematica notebook by emailing [email protected]: 40 pages, 16 figure
Secondary Prevention of Suicide
Leo Sher and colleagues discuss recent research on interventions to prevent secondary suicide and discuss the additional research that is needed
Effective theory of the Delta(1232) in Compton scattering off the nucleon
We formulate a new power-counting scheme for a chiral effective field theory
of nucleons, pions, and Deltas. This extends chiral perturbation theory into
the Delta-resonance region. We calculate nucleon Compton scattering up to
next-to-leading order in this theory. The resultant description of existing
p cross section data is very good for photon energies up to about 300
MeV. We also find reasonable numbers for the spin-independent polarizabilities
and .Comment: 29 pp, 9 figs. Minor revisions. To be published in PR
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