16823238
The Earth Mantle-Core Effect in Matter-Induced Asymmetries for Atmospheric Neutrino Oscillations
Earth medium effects in the three-neutrino oscillations of atmospheric neutrinos are observable under appropriate conditions. This paper generalizes the study of the medium effects and the possibility of their observation in the atmospheric neutrino oscillations from the case of neutrinos traversing only the Earth mantle, where the density is essentially constant, to the case of atmospheric neutrinos crossing also the Earth core. In the latter case new resonance-like effects become apparent. We calculate the CPT-odd asymmetry for the survival probability of muon neutrinos and the observable muon-charge asymmetry, taking into account the different atmospheric
39400765
Black hole evaporation in a thermalized final-state projection model
We propose a modified version of the Horowitz-Maldacena final-state boundary condition based upon a matter-radiation thermalization hypothesis on the Black Hole interior, which translates into a particular entangled state with thermal Schmidt coefficients. We investigate the consequences of this proposal for matter entering the horizon, as described by a Canonical density matrix characterized by the matter temperature T. The emitted radiation is explicitly calculated and is shown to follow a thermal spectrum with an effective temperature T{sub eff}. We analyze the evaporation process in the quasistatic approximation, highlighting important differences in the late stages with respect to the usual semiclassical evolution, and calculate the fidelity of the emitted Hawking radiation relative to the infalling matter.
119425946
Direct URCA process in neutron stars with strong magnetic fields
We calculate the emissivity for the direct URCA process in strongly magnetized, degenerate matter in neutron stars, under β-equilibrium. We show that, if the magnetic field is large enough for protons and electrons to be confined to their ground Landau levels, the field-free threshold condition on proton concentration no longer holds, and direct URCA reactions are open for an arbitrary proton concentration. Direct URCA process leads to an early phase of fast neutron star cooling. This circumstance allows us to constrain the initial magnetic field inside observed pulsars.
119371304
Neutrino-nucleon scattering rate in proto-neutron star matter
Abstract:We present a calculation of the neutrino-nucleon scattering cross-section which takes into account the nuclear correlations in the relativistic random phase approximation (RPA). Our approach is based on a quantum-hadrodynamics model with exchange of σ, ω, π, ρ and δ mesons. In view of applications to neutrino transport in the final stages of supernova explosion and proto-neutron star cooling, we study the evolution of the neutrino mean free path as a function of density, proton-neutron asymmetry and temperature. Special attention was paid to the issues of renormalization of the Dirac sea, residual interactions in the tensor channel, coupling to the delta-meson and meson mixing. In contrast with the results of other authors, we find that the neutral-current process is not sensitive to the strength g' of the residual contact interaction. As a consequence, it is found that RPA corrections with respect to the mean-field approximation amount to only 10% to 15% at high density.
119094287
Equilibrium properties of self-interacting neutrinos in the quasi-particle approach
In this work, a neutrino gas in equilibrium is studied both at T = 0 and at finite temperature. Neutrinos are treated as massive Dirac quasi-particles with two generations. We include self-interactions among the neutrinos via neutral currents, as well as the interaction with a background of matter. To obtain the equilibrium properties, we use Wigner function techniques. To account for corrections beyond the Hartree approximation, we also introduce correlation functions. We prove that, under the quasi-particle approximation, these correlation functions can be expressed as products of Wigner functions. We analyse the main properties of the neutrino eigenmodes in the medium, such as effective masses and mixing angle. We show that the formulae describing these quantities will differ with respect to the case with no self-interactions.
14718218
Nucleon–nucleon effective potential in dense matter including rho-meson exchange
Abstract We obtain the RPA summed one-meson exchange potential between nucleons in symmetric nuclear matter at zero temperature, from a model which includes ρ , σ , ω and π mesons. The behavior of rho mesons inside the medium is first discussed using different schemes to extract a finite contribution from the vacuum polarization. These schemes give qualitatively different results for the in-medium rho mass. The results are discussed in connection with the nonrenormalizability of the model. We next study the modified potential as density increases. In the intermediate-distance range, it is qualitatively modified by matter and vacuum effects. In the long-distance range ( r >2 fm), one observes the presence of oscillations, which are not present in free space. Features on this distance range are insensitive to the renormalization scheme.
18208486
Characterizing exact solutions from asymptotic physical concepts
We contribute to the subject of the physical interpretation of exact solutions by characterizing them through a systematic study in terms of unambiguous physical concepts coming from systems in linearized gravity. We use the physical meaning of the leading order behavior of the Weyl spinor components $\Psi_0^0$, $\Psi_1^0$ and $\Psi_2^0$ and of the Maxwell spinor components $\phi_0^0$ and $\phi_1^0$ and integrate from future null infinity inwards the exact field equations. In this way it is assigned an unambiguous physical meaning to exact solutions. We indicate a method to generalize the procedure to radiating spacetimes.
11836156
Measurement of the angle alpha at BABAR
The authors present recent measurements of the CKM angle {alpha} using data collected by the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at the SLAC National Accelerator Laboratory, operating at the {Upsilon}(4S) resonance. They present constraints on {alpha} from B {yields} {pi}{pi}, B {yields} {rho}{rho} and B {yields} {rho}{pi} decays.
119281747
Regular isolated black holes
We review a recently introduced1 approach to study spacetimes which contain an isolated black hole. We allow for gravitational radiation to fall through the event horizon and/or to be radiated at infinity. The crucial idea in our setting is the introduction of physical coordinates that have the meaning of being null hypersurfaces near the horizon and in a neighborhood of future null infinity. These spacetimes have remarkable properties, as for example a generalized notion of surface gravity κH.
118820970
Multiple-Event Probability in General-Relativistic Quantum Mechanics
We discuss the definition of quantum probability in the context of “timeless” general–relativistic quantum mechanics. In particular, we study the probability of sequences of events, or multi-event probability. In conventional quantum mechanics this can be obtained by means of the “wave function collapse” algorithm. We first point out certain difficulties of some natural definitions of multi-event probability, including the conditional probability widely considered in the literature. We then observe that multi-event probability can be reduced to single-event probability, by taking into account the quantum nature of the measuring apparatus. In fact, by exploiting the vonNeumann freedom of moving the quantum/classical boundary, one can always trade a sequence of non-commuting quantum measurements at different times, with an ensemble of simultaneous commuting measurements on the joint system+apparatus system. This observation permits a formulation of quantum theory based only on single-event probability, where the results of the “wave function collapse” algorithm can nevertheless be recovered. The discussion bears also on the nature of the quantum collapse.
118421024
Two-dimensional topological field theories coupled to four-dimensional BF theory
Four-dimensional BF theory admits a natural coupling to extended sources supported on two-dimensional surfaces or string world sheets. Solutions of the theory are in one to one correspondence with solutions of Einstein equations with distributional matter (cosmic strings). We study new (topological field) theories that can be constructed by adding extra degrees of freedom to the two-dimensional world sheet. We show how two-dimensional Yang-Mills degrees of freedom can be added on the world sheet, producing in this way, an interactive (topological) theory of Yang-Mills fields with BF fields in four dimensions. We also show how a world sheet tetrad can be naturally added. As in the previous case the set of solutions of these theories are contained in the set of solutions of Einstein's equations if one allows distributional matter supported on two-dimensional surfaces. These theories are argued to be exactly quantizable. In the context of quantum gravity, one important motivation to study these models is to explore the possibility of constructing a background-independent quantum field theory where local degrees of freedom at low energies arise from global topological (world sheet) degrees of freedom at the fundamental level.