122742819
Implications of the Discovery of Sub-Millisecond Pulsar in SN1987A
3Me companion object, it seems hard to account for such an object in the scenario of the supernova explosion. We estim;tte the magnetic field, ellipticity and the mass of the neutron star and also the period of glitches.
118908804
Multigroup simulation of protoneutron star cooling and neutrino spectra
122249200
Constraining neutrino oscillation parameters with future observations of supernova neutrinos by various types of detectors
We evaluate the potential for constraining neutrino oscillation parameters with future observations of supernova neutrinos. For some selected oscillation parameters, we calculate the expected energy spectra and angular distributions of neutrino events in various detectors (Super-Kamiokande, ICARUS, KamLAND and IceCube) for an assumed galactic core-collapse supernova. We investigate to what extent the oscillation parameters could be constrained using χ2 analysis when the expected events are really observed.
122604041
NEUTRINOS FROM PROTONEUTRON STARS
We performed numerical simulations of the quasistatic evolution of protoneutron star with neutrino transfer using multigroup flux limited diffusion scheme. The second half of the supernova neutrinos are emitted in this stage. We found 1) the flux decays rapidly and its mean energy falls below j/e's mean energy at the late stage, 2) Pe's carry out energy of about 24% of the total energy emitted in this cooling phase, and 3) the time-integrated energy spectra of u^s and v^s can be roughly fitted by the Fermi-Dirac spectra with positive chemical potentials while those of the other neutrinos can be fitted by MaxwellBoltzmann spectra. These results suggest that the total energy of the neutrino burst from SN1987A was overestimated if one assumed that the Pe's spectrum is the Fermi-Dirac one with a vanishing chemical potential and that all species of neutrinos contribute equally.
118715119
EFFECTS OF RESISTIVITY ON MAGNETIZED CORE-COLLAPSE SUPERNOVAE
We studied the role of turbulent resistivity in the core-collapse of a strongly magnetized massive star, carrying out two-dimensional resistive-MHD simulations. Three cases with different initial strengths of magnetic field and rotation are investigated: (1) a strongly magnetized rotating core, (2) a moderately magnetized rotating core, and (3) a very strongly magnetized non-rotating core. In each case, one ideal-MHD model and two resistive-MHD models are computed. As a result of these computations, each model shows an eruption of matter assisted by magnetic acceleration (and also by centrifugal acceleration in the rotating cases). We found that resistivity attenuates the explosion in cases 1 and 2, while it enhances the explosion in case 3. We also found that in the rotating cases, the main mechanisms for the amplification of a magnetic field in the post-bounce phase are an outward advection of the magnetic field and a twisting of poloidal magnetic field lines by differential rotation, which are somewhat dampened down with the presence of resistivity. Although magnetorotational instability seems to occur in the rotating models, it plays only a minor role in magnetic field amplification. Another impact of resistivity is that on the aspect ratio. In the rotating cases, a large aspect ratio of the ejected matter, >2.5, attained in an ideal-MHD model is reduced to some extent in a resistive model. These results indicate that resistivity possibly plays an important role in the dynamics of strongly magnetized supernovae.
119251795
Global Simulations of Magnetorotational Instability in the Collapsed Core of a Massive Star
We performed the first global numerical simulations of magnetorotational instability from a sub-magnetar-class seed magnetic field in core-collapse supernovae. As a result of axisymmetric ideal MHD simulations, we found that the magnetic field is greatly amplified to magnetar-class strength. In the saturation phase, a substantial part of the core is dominated by turbulence, and the magnetic field possesses dominant large-scale components, comparable to the size of a proto-neutron star. A pattern of coherent channel flows, which generally appears during the exponential growth phase in previous local simulations, is not observed in our global simulations. While the approximate convergence in the exponential growth rate is attained by increasing spatial resolution, that of the saturation magnetic field is not achieved due to still large numerical diffusion. Although the effect of the magnetic field on the dynamics is found to be mild, a simulation with a high enough resolution might result in a larger impact.
14702420
Improved Convergence Proof of the Delta Expansion and Order Dependent Mappings
Abstract We improve and generalize in several accounts the recent rigorous proof of convergence of delta expansion–order dependent mappings (variational perturbation expansion) for the energy eigenvalues of quartic anharmonic oscillator. For the single-well oscillator the uniformity of convergence in g ∈[0, ∞] is proven. The convergence proof is extended also to complex values of g lying on a wide domain of the Riemann surface of E ( g ). Via the scaling relation a la Symanzik, this proves the convergence of delta expansion for the double well in the strong coupling regime (where the standard perturbation series is non Borel summable), as well as for the complex “energy eigenvalues” in certain metastable systems. Difficulties in extending the convergence proof to the cases of higher anharmonic oscillators are pointed out. Sufficient conditions for the convergence of delta expansion are summarized in the form of three general theorems, which should apply to a wide class of quantum mechanical and higher dimensional field theoretic systems.
16618542
Renormalon's contribution to effective couplings
When an asymptotically non-free theory possesses a mass parameter independent of the Λ parameter, the uv renormalon gives rise to nonperturbative contributions, to dimension-four operators and dimensionless couplings, thus has a "dual" effect of the instanton. We illustrate this phenomenon in O(N) symmetric massive λϕ4 model in the 1/N expansion. This effect of uv renormalon is briefly compared with nonperturbative corrections in the magnetic picture of the Seiberg–Witten theory.
6971062
On the lattice construction of electroweak gauge theory
Abstract Based on the Ginsparg-Wilson relation, a gauge invariant formulation of electroweak SU(2) × U(1) gauge theory on the lattice is considered. If the hypercharge gauge coupling is turned off in the vacuum sector of the U(1) gauge fields, the theory consists of four left-handed SU(2) doublets and it is possible, as in vector-like theories, to make the fermion measure defined globally in all topological sectors of SU(2). We then try to incorporate U(1) gauge field, following Luscher's reconstruction theorem. The global integrability condition is proved for “gauge loops” in the space of the U(1) gauge fields with arbitrary SU(2) gauge field fixed in the background. For “non-gauge loops”, however, the proof is given so far only for the classical SU(2) instanton backgrounds.
117782816
Solar and supernova neutrinos and the MSW effect.
119251656
Large-N limit of the gradient flow in the 2D O(N) nonlinear sigma model
The gradient flow equation in the 2D $O(N)$ nonlinear sigma model with lattice regularization is solved in the leading order of the $1/N$ expansion. By using this solution, we analytically compute the thermal expectation value of a lattice energy--momentum tensor defined through the gradient flow. The expectation value reproduces thermodynamic quantities obtained by the standard large-$N$ method. This analysis confirms that the above lattice energy--momentum tensor restores the correct normalization automatically in the continuum limit, in a system with a non-perturbative mass gap.