819 research outputs found

    The historical origins of the American Peace Test

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    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

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    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

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    In this work, we have investigated the validity of GSL of thermodynamics in a universe (open, closed and flat) governed by Horˇ\check{\text r}ava-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

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    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

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    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 ω\omega\rightarrow \infty, 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 3{}^3He

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    Motivated by the fact that a polarized 3{}^3He 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 (O(e2Q){\mathcal O}(e^2 Q)) at energies, ωmπ\omega \leq m_{\pi}, where mπm_{\pi} 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

    Effective theory of the Delta(1232) in Compton scattering off the nucleon

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    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 γ\gammap cross section data is very good for photon energies up to about 300 MeV. We also find reasonable numbers for the spin-independent polarizabilities αp\alpha_p and βp\beta_p.Comment: 29 pp, 9 figs. Minor revisions. To be published in PR
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