Statistical Properties of Fermionic Molecular Dynamics

Statistical properties of Fermionic Molecular Dynamics are studied. It is shown that, although the centroids of the single--particle wave--packets follow classical trajectories in the case of a harmonic oscillator potential, the equilibrium properties of the system are the quantum mechanical ones. A system of weakly interacting fermions as well as of distinguishable particles is found to be ergodic and the time--averaged occupation probabilities approach the quantum canonical ones of Fermi--Dirac and Boltzmann statistics, respectively.Comment: 16 pages, several postscript figures, uses 'epsfig.sty'. More information is available at http://www.gsi.de/~schnack/fmd.htm

INCORPORATION OF QUANTUM STATISTICAL FEATURES IN MOLECULAR DYNAMICS

We formulate a method for incorporating quantum fluctuations into molecular- dynamics simulations of many-body systems, such as those employed for energetic nuclear collision processes. Based on Fermi's Golden Rule, we allow spontaneous transitions to occur between the wave packets which are not energy eigenstates. The ensuing diffusive evolution in the space of the wave packet parameters exhibits appealing physical properties, including relaxation towards quantum- statistical equilibrium.Comment: 8 latex pages + 1 uuencoded ps figur

Tables of Hyperonic Matter Equation of State for Core-Collapse Supernovae

We present sets of equation of state (EOS) of nuclear matter including hyperons using an SU_f(3) extended relativistic mean field (RMF) model with a wide coverage of density, temperature, and charge fraction for numerical simulations of core collapse supernovae. Coupling constants of Sigma and Xi hyperons with the sigma meson are determined to fit the hyperon potential depths in nuclear matter, U_Sigma(rho_0) ~ +30 MeV and U_Xi(rho_0) ~ -15 MeV, which are suggested from recent analyses of hyperon production reactions. At low densities, the EOS of uniform matter is connected with the EOS by Shen et al., in which formation of finite nuclei is included in the Thomas-Fermi approximation. In the present EOS, the maximum mass of neutron stars decreases from 2.17 M_sun (Ne mu) to 1.63 M_sun (NYe mu) when hyperons are included. In a spherical, adiabatic collapse of a 15$M_\odot$ star by the hydrodynamics without neutrino transfer, hyperon effects are found to be small, since the temperature and density do not reach the region of hyperon mixture, where the hyperon fraction is above 1 % (T > 40 MeV or rho_B > 0.4 fm^{-3}).Comment: 23 pages, 6 figures (Fig.3 and related comments on pion potential are corrected in v3.

Multi-phases in gauge theories on non-simply connected spaces

It is pointed out that phase structures of gauge theories compactified on non-simply connected spaces are not trivial. As a demonstration, an SU(2) gauge model on $M^3\otimes S^1$ is studied and is shown to possess three phases: Hosotani, Higgs and coexisting phases. The critical radius and the order of the phase transitions are explicitly determined. A general discussion about phase structures for small and large scales of compactified spaces is given. The appearance of phase transitions suggests a GUT scenario in which the gauge hierarchy problem is replaced by a dynamical problem of how to stabilize a radius of a compactified space in close vicinity to a critical radius.Comment: 12 pages, 1 figur

The g-mode Excitation in the Proto Neutron Star by the Standing Accretion Shock Instability

The so-called "acoustic revival mechanism" of core-collapse supernova proposed recently by the Arizona group is an interesting new possibility. Aiming to understand the elementary processes involved in the mechanism, we have calculated the eigen frequencies and eigen functions for the g-mode oscillations of a non-rotating proto neutron star. The possible excitation of these modes by the standing accretion shock instability, or SASI, is discussed based on these eigen functions. We have formulated the forced oscillations of $g$-modes by the external pressure perturbations exerted on the proto neutron star surface. The driving pressure fluctuations have been adopted from our previous computations of the axisymmetric SASI in the non-linear regime. We have paid particular attention to low l modes, since these are the modes that are dominant in SASI and that the Arizona group claimed played an important role in their acoustic revival scenario. Here l is the index of the spherical harmonic functions, $Y_l^m$. Although the frequency spectrum of the non-linear SASI is broadened substantially by non-linear couplings, the typical frequency is still much smaller than those of g-modes, the fact leading to a severe impedance mismatch. As a result, the excitations of various $g$-modes are rather inefficient and the energy of the saturated g-modes is $\sim 10^{50}$erg or smaller, with the g_2-mode being the largest in our model. Here the g_2-mode has two radial nodes and is confined to the interior of the convection region. The energy transfer rate from the g-modes to out-going sound waves is estimated from the growth of the g-modes and found to be $\sim 10^{51}$erg/s in the model studied in this paper.Comment: 24 pages, 6 figure

Design of a Broadband Amplifier for High Speed Applications

This paper provides comprehensive insight into the design approach followed for an amplifier dedicated to high speed base band signals. To demonstrate the methodology, an amplifier consisting of nine PHEMT cascode cells within a distributed amplifier topology was designed. The resulting frequency response is 40 GHz at the 3-dB point, and the output voltage for a 43 Gbps eye diagram is 7.3 Vpp at the chip terminal

Three-Dimensional Simulations of Standing Accretion Shock Instability in Core-Collapse Supernovae

We have studied non-axisymmetric standing accretion shock instability, or SASI, by 3D hydrodynamical simulations. This is an extention of our previous study on axisymmetric SASI. We have prepared a spherically symmetric and steady accretion flow through a standing shock wave onto a proto-neutron star, taking into account a realistic equation of state and neutrino heating and cooling. This unperturbed model is supposed to represent approximately the typical post-bounce phase of core-collapse supernovae. We then have added a small perturbation (~1%) to the radial velocity and computed the ensuing evolutions. Not only axisymmetric but non-axisymmetric perturbations have been also imposed. We have applied mode analysis to the non-spherical deformation of the shock surface, using the spherical harmonics. We have found that (1) the growth rates of SASI are degenerate with respect to the azimuthal index m of the spherical harmonics Y_l^m, just as expected for a spherically symmetric background, (2) nonlinear mode couplings produce only m=0 modes for the axisymmetric perturbations, whereas m=!0 modes are also generated in the non-axisymmetric cases according to the selection rule for the quadratic couplings, (3) the nonlinear saturation level of each mode is lower in general for 3D than for 2D because a larger number of modes are contributing to turbulence in 3D, (4) low l modes are dominant in the nonlinear phase, (5) the equi-partition is nearly established among different m modes in the nonlinear phase, (6) the spectra with respect to l obey power laws with a slope slightly steeper for 3D, and (7) although these features are common to the models with and without a shock revival at the end of simulation, the dominance of low l modes is more remarkable in the models with a shock revival.Comment: 37 pages, 16 figures, and 1 table, submitted to Ap