384 research outputs found

    Coulomb Force as an Entropic Force

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    Motivated by Verlinde's theory of entropic gravity, we give a tentative explanation to Coulomb's law with an entropic force. When trying to do this, we find the equipartition rule should be extended to charges and the concept of temperature should be reinterpreted. If one accepts the holographic principle as well as our generalizations and reinterpretations, then Coulomb's law, the Poisson equation and the Maxwell equations can be derived smoothly. Our attempt can be regarded as a new way to unify the electromagnetic force with gravity, from the entropic origin. Possibly some of our postulates are related to the D-brane picture of black hole thermodynamics.Comment: discussion and bibliography update

    Cosmic Steps in Modeling Dark Energy

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    The past and recent data analyses gave some hints of steps in dark energy. Considering the dark energy as a dynamical scalar field, we investigate several models with various steps: a step in the scalar potential, a step in the kinetic term, a step in the energy density and a step in the equation-of-state parameter w. These toy models provide a workable mechanism to generate steps and features of dark energy. Remarkably, a single real scalar can cross w=-1 dynamically with a step in the kinetic term.Comment: 6 pages, 5 figures, structure improved, reference added, results unchange

    General Single Field Inflation with Large Positive Non-Gaussianity

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    Recent analysis of the WMAP three year data suggests fNLlocal86.8f_{NL}^{local}\simeq86.8 in the WMAP convention. It is necessary to make sure whether general single field inflation can produce a large positive fNLf_{NL} before turning to other scenarios. We give some examples to generate a large positive fNLequilf_{NL}^{equil} in general single field inflation. Our models are different from ghost inflation. Due to the appearance of non-conventional kinetic terms, fNLequil1f_{NL}^{equil}\gg1 can be realized in single field inflation.Comment: 27 pages, 3 figure; final version published in JCA

    Inflation with High Derivative Couplings

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    We study a class of generalized inflation models in which the inflaton is coupled to the Ricci scalar by a general f(ϕ,R)f(\phi, R) term. The scalar power spectrum, the spectral index, the running of the spectral index, the tensor mode spectrum and a new consistency relation of the model are calculated. We discuss in detail the issues of how to diagonize the coupled perturbation equations, how to deal with an entropy-like source, and how to determine the initial condition by quantization. By studying some explicit models, we find that rich phenomena such as a blue scalar power spectrum, a large running of the spectral index, and a blue tensor mode spectrum can be obtained.Comment: 26 pages, LaTeX; v2: refs. added; refs. correcte