Massive Spin-2 fields of Geometric Origin in Curved Spacetimes

We study the consistency of a model which includes torsion as well as the metric as dynamical fields and has massive spin-2 particle in its spectrum. The massive spin-2 mode resides in the torsion, rather than in the metric. It is known that this model is tachyon- and ghost-free in Minkowski background. We show that this property remains valid and no other pathologies emerge in de Sitter and anti-de Sitter backgrounds, with some of our results extending to arbirary Einstein space backgrounds. This suggests that the model is consistent, at least at the classical level, unlike, e.g., the Fierz--Pauli theory.Comment: 17 pages, Clarifying remarks added in section 5, minor changes, version to be published in the Phys. Rev.

Nuclear Magnetic Relaxation Rate in a Noncentrosymmetric Superconductor

For a noncentrosymmetric superconductor such as CePt3Si, we consider a Cooper pairing model with a two-component order parameter composed of spin-singlet and spin-triplet pairing components. We demonstrate that such a model on a qualitative level accounts for experimentally observed features of the temperature dependence of the nuclear spin-lattice relaxation rate 1/T1, namely a peak just below Tc and a line-node gap behavior at low temperatures.Comment: 4 page

Quantum hypothesis testing with group symmetry

The asymptotic discrimination problem of two quantum states is studied in the setting where measurements are required to be invariant under some symmetry group of the system. We consider various asymptotic error exponents in connection with the problems of the Chernoff bound, the Hoeffding bound and Stein's lemma, and derive bounds on these quantities in terms of their corresponding statistical distance measures. A special emphasis is put on the comparison of the performances of group-invariant and unrestricted measurements.Comment: 33 page

Exponents of quantum fixed-length pure state source coding

We derive the optimal exponent of the error probability of the quantum fixed-length pure state source coding in both cases of blind coding and visible coding. The optimal exponent is universally attained by Jozsa et al. (PRL, 81, 1714 (1998))'s universal code. In the direct part, a group representation theoretical type method is essential. In the converse part, Nielsen and Kempe (PRL, 86, 5184 (2001))'s lemma is essential.Comment: LaTeX2e and revetx4 with aps,twocolumn,superscriptaddress,showpacs,pra,amssymb,amsmath. The previous version has a mistak

Path Integral for Space-time Noncommutative Field Theory

The path integral for space-time noncommutative theory is formulated by means of Schwinger's action principle which is based on the equations of motion and a suitable ansatz of asymptotic conditions. The resulting path integral has essentially the same physical basis as the Yang-Feldman formulation. It is first shown that higher derivative theories are neatly dealt with by the path integral formulation, and the underlying canonical structure is recovered by the Bjorken-Johnson-Low (BJL) prescription from correlation functions defined by the path integral. A simple theory which is non-local in time is then analyzed for an illustration of the complications related to quantization, unitarity and positive energy conditions. From the view point of BJL prescription, the naive quantization in the interaction picture is justified for space-time noncommutative theory but not for the simple theory non-local in time. We finally show that the perturbative unitarity and the positive energy condition, in the sense that only the positive energy flows in the positive time direction for any fixed time-slice in space-time, are not simultaneously satisfied for space-time noncommutative theory by the known methods of quantization.Comment: 21 page

Nuclear transport models can reproduce charged-particle-inclusive measurements but are not strongly constrained by them

Nuclear transport models are important tools for interpretation of many heavy-ion experiments and are essential in efforts to probe the nuclear equation of state. In order to fulfill these roles, the model predictions should at least agree with observed single-particle-inclusive momentum spectra; however, this agreement has recently been questioned. The present work compares the Vlasov-Uehling-Uhlenbeck model to data for mass-symmetric systems ranging from 12C+12C to 139La+139La, and we find good agreement within experimental uncertainties at 0.4A and 0.8A GeV. For currently available data, these uncertainties are too large to permit effective nucleon-nucleon scattering cross sections in the nuclear medium to be extracted at a useful level of precision

Charge transfer and weak bonding between molecular oxygen and graphene zigzag edges at low temperatures

Electron paramagnetic resonance (EPR) study of air-physisorbed defective carbon nano-onions evidences in favor of microwave assisted formation of weakly-bound paramagnetic complexes comprising negatively-charged O2- ions and edge carbon atoms carrying pi-electronic spins. These complexes being located on the graphene edges are stable at low temperatures but irreversibly dissociate at temperatures above 50-60 K. These EPR findings are justified by density functional theory (DFT) calculations demonstrating transfer of an electron from the zigzag edge of graphene-like material to oxygen molecule physisorbed on the graphene sheet edge. This charge transfer causes changing the spin state of the adsorbed oxygen molecule from S = 1 to S = 1/2 one. DFT calculations show significant changes of adsorption energy of oxygen molecule and robustness of the charge transfer to variations of the graphene-like substrate morphology (flat and corrugated mono- and bi-layered graphene) as well as edges passivation. The presence of H- and COOH- terminated edge carbon sites with such corrugated substrate morphology allows formation of ZE-O2- paramagnetic complexes characterized by small (<50 meV) binding energies and also explains their irreversible dissociation as revealed by EPR.Comment: 28 pages, 8 figures, 2 tables, accepted in Carbon journa

Neumann problem for the Korteweg–de Vries equation

AbstractWe consider Neumann initial-boundary value problem for the Korteweg–de Vries equation on a half-line(0.1){ut+λuux+uxxx=0,t>0,x>0,u(x,0)=u0(x),x>0,ux(0,t)=0,t>0. We prove that if the initial data u0∈H10,214∩H21,72 and the norm ‖u0‖H10,214+‖u0‖H21,72⩽ε, where ε>0 is small enough Hps,k={f∈L2;‖f‖Hps,k=‖〈x〉k〈i∂x〉sf‖Lp<∞}, 〈x〉=1+x2 and λ∫0∞xu0(x)dx=λθ<0. Then there exists a unique solution u∈C([0,∞),H21,72)∩L2(0,∞;H22,3) of the initial-boundary value problem (0.1). Moreover there exists a constant C such that the solution has the following asymptoticsu(x,t)=Cθ(1+ηlogt)−1t−23Ai′(xt3)+O(ε2t−23(1+ηlogt)−65) for t→∞ uniformly with respect to x>0, where η=−9θλ∫0∞Ai′2(z)dz and Ai(q) is the Airy functionAi(q)=12πi∫−i∞i∞e−z3+zqdz=1πRe∫0∞e−iξ3+iξqdξ

Two-dimensional radiation-hydrodynamic model for limit-cycle oscillations of luminous accretion disks

We investigate the time evolution of luminous accretion disks around black holes, conducting the two-dimensional radiation-hydrodynamic simulations. We adopt the alpha prescription for the viscosity. The radial-azimuthal component of viscous stress tensor is assumed to be proportional to the total pressure in the optically thick region, while the gas pressure in the optically thin regime. The viscosity parameter, alpha, is taken to be 0.1. We find the limit-cycle variation in luminosity between high and low states. When we set the mass input rate from the outer disk boundary to be 100 L_E/c^2, the luminosity suddenly rises from 0.3L_E to 2L_E, where L_E is the Eddington luminosity. It decays after retaining high value for about 40 s. Our numerical results can explain the variation amplitude and duration of the recurrent outbursts observed in microquasar, GRS 1915+105. We show that the multi-dimensional effects play an important role in the high-luminosity state. In this state, the outflow is driven by the strong radiation force, and some part of radiation energy dissipated inside the disk is swallowed by the black hole due to the photon-trapping effects. This trapped luminosity is comparable to the disk luminosity. We also calculate two more cases: one with a much larger accretion rate than the critical value for the instability and the other with the viscous stress tensor being proportional to the gas pressure only even when the radiation pressure is dominant. We find no quasi-periodic light variations in these cases. This confirms that the limit-cycle behavior found in the simulations is caused by the disk instability.Comment: 6 pages, 4 figures, accepted for publication in ApJ (ApJ 01 April 2006, v640, 2 issue