Reheat temperature in supersymmetric hybrid inflation models

The allowed range of parameters for supersymmetric hybrid inflation and its extensions are investigated. The lower bound on the reheat temperature T_r in these models with hierarchical right handed neutrinos is found to be 3*10^7 GeV. (T_r as low as 100 GeV is possible for quasi degenerate right handed neutrinos.) We also present revised estimates for the scalar spectral index and the symmetry breaking scale associated with inflation.Comment: 15 pages, 8 figures, revtex4. v2: minor changes, matches published versio

De Sitter space and perpetuum mobile

We give general arguments that any interacting non--conformal {\it classical} field theory in de Sitter space leads to the possibility of constructing a perpetuum mobile. The arguments are based on the observation that massive free falling particles can radiate other massive particles on the classical level as seen by the free falling observer. The intensity of the radiation process is non-zero even for particles with any finite mass, i.e. with a wavelength which is within the causal domain. Hence, we conclude that either de Sitter space can not exist eternally or that one can build a perpetuum mobile.Comment: 11 pages revtex, no figures. Added discussion to strengthen conclusio

Linking solar and long baseline terrestrial neutrino experiments

We show that in the framework of three light neutrino species with hierarchical masses and assuming no fine tuning between the entries of the neutrino mass matrix, one can use the solar neutrino data to obtain information on the element $U_{e3}$ of the lepton mixing matrix. Conversely, a measurement of $U_{e3}$ in atmospheric or long baseline accelerator or reactor neutrino experiments would help discriminate between possible oscillation solutions of the solar neutrino problem.Comment: revtex, 4 pages, no figures. Discussion of the LOW solution modified; results unchanged. References adde

The MSW effect and Matter Effects in Neutrino Oscillations

The MSW (Mikheyev-Smirnov-Wolfenstein) effect is the adiabatic or partially adiabatic neutrino flavor conversion in medium with varying density. The main notions related to the effect, its dynamics and physical picture are reviewed. The large mixing MSW effect is realized inside the Sun providing the solution of the solar neutrino problem. The small mixing MSW effect driven by the 1-3 mixing can be realized for the supernova (SN) neutrinos. Inside the collapsing stars new elements of the MSW dynamics may show up: the non-oscillatory transition, non-adiabatic conversion, time dependent adiabaticity violation induced by shock waves. Effects of the resonance enhancement and the parametric enhancement of oscillations can be realized for the atmospheric and accelerator neutrinos in the Earth. Precise results for neutrino oscillations in the low density medium with arbitrary density profile are presented and the attenuation effect is described. The area of applications is the solar and SN neutrinos inside the Earth, and the results are crucial for the neutrino oscillation tomography.Comment: 18 pages, latex, 6 figures, talk given at the Nobel Symposium 129, ``Neutrino Physics'', Haga Slott, August 19 - 24, 200

Neutrino conversions in random magnetic fields and ν~e\tilde{\nu}_e from the Sun

The magnetic field in the convective zone of the Sun has a random small-scale component with the r.m.s. value substantially exceeding the strength of a regular large-scale field. For two Majorana neutrino flavors $\times$ two helicities in the presence of a neutrino transition magnetic moment and nonzero neutrino mixing we analyze the displacement of the allowed ($\Delta m^2- \sin^22\theta$)-parameter region reconciled for the SuperKamiokande(SK) and radiochemical (GALLEX, SAGE, Homestake) experiments in dependence on the r.m.s. magnetic field value $b$, or more precisely, on a value $\mu b$ assuming the transition magnetic moment $\mu = 10^{-11}\mu_B$. In contrast to RSFP in regular magnetic fields we find an effective production of electron antineutrinos in the Sun even for small neutrino mixing through cascade conversions $\nu_{eL}\to \nu_{\mu L}\to \tilde{\nu}_{eR}$, $\nu_{eL}\to \nu_{\mu R}\to \tilde{\nu}_{eR}$ in a random magnetic field that would be a signature of the Majorana nature of neutrino if $\tilde{\nu}_{eR}$ will be registered. Basing on the present SK bound on electron antineutrinos we have also found an excluded area in the same $\Delta m^2,~\sin^22\theta$-plane and revealed a strong sensitivity to the random magnetic field correlation length $L_0$.Comment: LaTex 36 pages including 14 PostScript figure

Neutrino oscillations in structured matter

A layered material structure in a monochromatic neutrino beam produces interference effects that could be used for the measurement of features of the neutrino mass matrix. The phenomenon would be most useful at high energies.Comment: 18 pp of which two figure

On the physical meaning of the Unruh effect

We present simple arguments that detectors moving with constant acceleration (even acceleration for a finite time) should detect particles. The effect is seen to be universal. Moreover, detectors undergoing linear acceleration and uniform, circular motion both detect particles for the same physical reason. We show that if one uses a circularly orbiting electron in a constant external magnetic field as the Unruh--DeWitt detector, then the Unruh effect physically coincides with the experimentally verified Sokolov--Ternov effect.Comment: 7 pages, 0 figures references added, small changes in text. To be published JETP Lett

Cornwall-Jackiw-Tomboulis effective potential for canonical noncommutative field theories

We apply the Cornwall-Jackiw-Tomboulis (CJT) formalism to the scalar $\lambda \phi^{4}$ theory in canonical-noncommutative spacetime. We construct the CJT effective potential and the gap equation for general values of the noncommutative parameter $\theta_{\mu\nu}$. We observe that under the hypothesis of translational invariance, which is assumed in the effective potential construction, differently from the commutative case ($\theta_{\mu\nu}= 0$), the renormalizability of the gap equation is incompatible with the renormalizability of the effective potential. We argue that our result, is consistent with previous studies suggesting that a uniform ordered phase would be inconsistent with the infrared structure of canonical noncommutative theories.Comment: 15 pages, LaTe