35,793 research outputs found

    Neutrino Constraints on Inelastic Dark Matter after CDMS II

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    We discuss the neutrino constraints from solar and terrestrial dark matter (DM) annihilations in the inelastic dark matter (iDM) scenario after the recent CDMS II results. To reconcile the DAMA/LIBRA data with constraints from all other direct experiments, the iDM needs to be light (mχ<100m_\chi < 100 GeV) and have a large DM-nucleon cross section (σn\sigma_n \sim 104^{-4} pb in the spin-independent (SI) scattering and σn\sigma_n \sim 10 pb in the spin-dependent (SD) scattering). The dominant contribution to the iDM capture in the Sun is from scattering off Fe/Al in the SI/SD case. Current bounds from Super-Kamiokande exclude the hard DM annihilation channels, such as W+WW^+W^-, ZZZZ, ttˉt\bar{t} and τ+τ\tau^+ \tau^-. For soft channels such as bbˉb\bar{b} and ccˉc \bar{c}, the limits are loose, but could be tested or further constrained by future IceCube plus DeepCore. For neutrino constraints from the DM annihilation in the Earth, due to the weaker gravitational effect of the Earth and inelastic capture condition, the constraint exists only for small mass splitting δ<\delta < 40 keV and mχ(10,50)m_\chi \sim (10, 50) GeV even in the τ+τ\tau^+ \tau^- channel.Comment: 11 pages, 8 figure

    Random solids and random solidification: What can be learned by exploring systems obeying permanent random constraints?

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    In many interesting physical settings, such as the vulcanization of rubber, the introduction of permanent random constraints between the constituents of a homogeneous fluid can cause a phase transition to a random solid state. In this random solid state, particles are permanently but randomly localized in space, and a rigidity to shear deformations emerges. Owing to the permanence of the random constraints, this phase transition is an equilibrium transition, which confers on it a simplicity (at least relative to the conventional glass transition) in the sense that it is amenable to established techniques of equilibrium statistical mechanics. In this Paper I shall review recent developments in the theory of random solidification for systems obeying permanent random constraints, with the aim of bringing to the fore the similarities and differences between such systems and those exhibiting the conventional glass transition. I shall also report new results, obtained in collaboration with Weiqun Peng, on equilibrium correlations and susceptibilities that signal the approach of the random solidification transition, discussing the physical interpretation and values of these quantities both at the Gaussian level of approximation and, via a renormalization-group approach, beyond.Comment: Paper presented at the "Unifying Concepts in Glass Physics" workshop, International Centre for Theoretical Physics, Trieste, Italy (September 15-18, 1999

    A discrete time-dependent method for metastable atoms in intense fields

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    The full-dimensional time-dependent Schrodinger equation for the electronic dynamics of single-electron systems in intense external fields is solved directly using a discrete method. Our approach combines the finite-difference and Lagrange mesh methods. The method is applied to calculate the quasienergies and ionization probabilities of atomic and molecular systems in intense static and dynamic electric fields. The gauge invariance and accuracy of the method is established. Applications to multiphoton ionization of positronium and hydrogen atoms and molecules are presented. At very high intensity above saturation threshold, we extend the method using a scaling technique to estimate the quasienergies of metastable states of the hydrogen molecular ion. The results are in good agreement with recent experiments.Comment: 10 pages, 9 figure, 4 table

    Formation and kinetics of transient metastable states in mixtures under coupled phase ordering and chemical demixing

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    We present theory and simulation of simultaneous chemical demixing and phase ordering in a polymer-liquid crystal mixture in conditions where isotropic- isotropic phase separation is metastable with respect to isotropic-nematic phase transition. It is found that mesophase formation proceeds by a transient metastable phase that surround the ordered phase, and whose lifetime is a function of the ratio of diffusional to orientational mobilities. It is shown that kinetic phase ordering in polymer-mesogen mixtures is analogous to kinetic crystallization in polymer solutions.Comment: 17 pages, 5 figures accepted for publication in EP

    η\eta-meson in nuclear matter

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    The η\eta-nucleon (η\etaN) interactions are deduced from the heavy baryon chiral perturbation theory up to the next-to-leading-order terms. Combining the relativistic mean-field theory for nucleon system, we have studied the in-medium properties of η\eta-meson. We find that all the elastic scattering η\etaN interactions come from the next-to-leading-order terms. The η\eta N sigma term is found to be about 280±\pm130 MeV. The off-shell terms are also important to the in-medium properties of η\eta-meson. On application of the latest determination of the η\etaN scattering length, the ratio of η\eta-meson effective mass to its vacuum value is near 0.84±0.0150.84\pm0.015, while the optical potential is about (83±5)-(83\pm5) MeV, at the normal nuclear density.Comment: 8 pages, 3 figures, to appear in PRC, many modification
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