595 research outputs found

    Invitation to the Table Conversation: A Few Diverse Perspectives on Integration

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    This article represents an invitation to the integration table to several previously underrepresented perspectives within Christian psychology. The Judeo-Christian tradition and current views on scholarship and Christian faith compel us to extend hospitality to minority voices within integration, thereby enriching and challenging existing paradigms in the field. Contributors to this article, spanning areas of cultural, disciplinary, and theological diversity, provide suggestions for how their distinct voices can enhance future integrative efforts

    Large entropy production inside black holes: a simple model

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    Particles dropped into a rotating black hole can collide near the inner horizon with enormous energies. The entropy produced by these collisions can be several times larger than the increase in the horizon entropy due to the addition of the particles. In this paper entropy is produced by releasing large numbers of neutrons near the outer horizon of a rotating black hole such that they collide near the inner horizon at energies similar to those achieved at the Relativistic Heavy Ion Collider. The increase in horizon entropy is approximately 80 per dropped neutron pair, while the entropy produced in the collisions is 160 per neutron pair. The collision entropy is produced inside the horizon, so this excess entropy production does not violate Bousso's bound limiting the entropy that can go through the black hole's horizon. The generalized laws of black hole thermodynamics are obeyed. No individual observer inside the black hole sees a violation of the second law of thermodynamicsComment: 10 page

    Sans measurement of deuterium trapping at dislocations and grain boundaries in palladium

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    Small angle neutron scattering (SANS) measurements have been made on deformed single crystal and polycrystalline palladium with and without deuterium dissolved in the solution phase at room temperature. The net scattering cross section for the same sample with and without deuterium loading shows a behavior expected from deuterium correlation with dislocations forming rod-like scattering structures. We conclude from these scattering measurements that the trapped deuterium is within 2-3 Burgers vectors of the dislocation core. On average 1-3 deuterons per A are trapped at dislocations in the deformed samples. The measurements indicate the straight, rod-like correlation geometry extends on average 50-100 A along the dislocations. Net scattering from a well annealed polycrystalline palladium sample exhibiting a behavior expected from surfaces has been observed. This net scattering is attributed to deuterium trapped at grain boundaries in the polycrystalline sample. A value of 0.4 +/- 0.2 trapped deuterons per A2 of grain boundary area is calculated from the well annealed polycrystalline scattering measurement.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29076/1/0000111.pd

    Entropy and universality of Cardy-Verlinde formula in dark energy universe

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    We study the entropy of a FRW universe filled with dark energy (cosmological constant, quintessence or phantom). For general or time-dependent equation of state p=wρp=w\rho the entropy is expressed in terms of energy, Casimir energy, and ww. The correspondent expression reminds one about 2d CFT entropy only for conformal matter. At the same time, the cosmological Cardy-Verlinde formula relating three typical FRW universe entropies remains to be universal for any type of matter. The same conclusions hold in modified gravity which represents gravitational alternative for dark energy and which contains terms growing at low curvature. It is interesting that BHs in modified gravity are more entropic than in Einstein gravity. Finally, some hydrodynamical examples testing new shear viscosity bound, which is expected to be the consequence of the holographic entropy bound, are presented for the early universe in the plasma era and for the Kasner metric. It seems that the Kasner metric provides a counterexample to the new shear viscosity bound.Comment: LaTeX file, 39 pages, references are adde

    Holographic Dark Energy Model and Scalar-Tensor Theories

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    We study the holographic dark energy model in a generalized scalar tensor theory. In a universe filled with cold dark matter and dark energy, the effect of potential of the scalar field is investigated in the equation of state parameter. We show that for a various types of potentials, the equation of state parameter is negative and transition from deceleration to acceleration expansion of the universe is possible.Comment: 11 pages, no figure. To appear in General Relativity and Gravitatio

    Gravitational Coupling and Dynamical Reduction of The Cosmological Constant

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    We introduce a dynamical model to reduce a large cosmological constant to a sufficiently small value. The basic ingredient in this model is a distinction which has been made between the two unit systems used in cosmology and particle physics. We have used a conformal invariant gravitational model to define a particular conformal frame in terms of large scale properties of the universe. It is then argued that the contributions of mass scales in particle physics to the vacuum energy density should be considered in a different conformal frame. In this manner, a decaying mechanism is presented in which the conformal factor appears as a dynamical field and plays a key role to relax a large effective cosmological constant. Moreover, we argue that this model also provides a possible explanation for the coincidence problem.Comment: To appear in GR

    Noise induced transitions in semiclassical cosmology

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    A semiclassical cosmological model is considered which consists of a closed Friedmann-Robertson-Walker in the presence of a cosmological constant, which mimics the effect of an inflaton field, and a massless, non-conformally coupled quantum scalar field. We show that the back-reaction of the quantum field, which consists basically of a non local term due to gravitational particle creation and a noise term induced by the quantum fluctuations of the field, are able to drive the cosmological scale factor over the barrier of the classical potential so that if the universe starts near zero scale factor (initial singularity) it can make the transition to an exponentially expanding de Sitter phase. We compute the probability of this transition and it turns out to be comparable with the probability that the universe tunnels from "nothing" into an inflationary stage in quantum cosmology. This suggests that in the presence of matter fields the back-reaction on the spacetime should not be neglected in quantum cosmology.Comment: LaTex, 33.tex pages, no figure

    Post-Newtonian SPH calculations of binary neutron star coalescence. I. Method and first results

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    We present the first results from our Post-Newtonian (PN) Smoothed Particle Hydrodynamics (SPH) code, which has been used to study the coalescence of binary neutron star (NS) systems. The Lagrangian particle-based code incorporates consistently all lowest-order (1PN) relativistic effects, as well as gravitational radiation reaction, the lowest-order dissipative term in general relativity. We test our code on sequences of single NS models of varying compactness, and we discuss ways to make PN simulations more relevant to realistic NS models. We also present a PN SPH relaxation procedure for constructing equilibrium models of synchronized binaries, and we use these equilibrium models as initial conditions for our dynamical calculations of binary coalescence. Though unphysical, since tidal synchronization is not expected in NS binaries, these initial conditions allow us to compare our PN work with previous Newtonian results. We compare calculations with and without 1PN effects, for NS with stiff equations of state, modeled as polytropes with Γ=3\Gamma=3. We find that 1PN effects can play a major role in the coalescence, accelerating the final inspiral and causing a significant misalignment in the binary just prior to final merging. In addition, the character of the gravitational wave signal is altered dramatically, showing strong modulation of the exponentially decaying waveform near the end of the merger. We also discuss briefly the implications of our results for models of gamma-ray bursts at cosmological distances.Comment: RevTeX, 37 pages, 17 figures, to appear in Phys. Rev. D, minor corrections onl

    Evidence of the Purely Leptonic Decay B- --> tau- nu_tau-bar

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    We present the first evidence of the decay B- --> tau- nu_tau-bar using 414 fb^-1 of data collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. Events are tagged by fully reconstructing one of the B mesons in hadronic modes. We detect the signal with a significance of 3.5 standard deviations including systematics, and measure the branching fraction to be Br(B- --> tau- nu_tau-bar) = (1.79 +0.56-0.49(stat) +0.46-0.51(syst))*10^-4. This implies that f_B = 0.229 +0.036-0.031(stat) +0.034-0.037(syst) GeV and is the first direct measurement of this quantity.Comment: 6 pages, 3 figures, to appear in Physical Review Letter
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