Anomalous Viscosity of an Expanding Quark-Gluon Plasma

We argue that an expanding quark-gluon plasma has an anomalous viscosity, which arises from interactions with dynamically generated color fields. We derive an expression for the anomalous viscosity in the turbulent plasma domain and apply it to the hydrodynamic expansion phase, when the quark-gluon plasma is near equilibrium. The anomalous viscosity dominates over the collisional viscosity for weak coupling and not too late times. This effect may provide an explanation for the apparent ``nearly perfect'' liquidity of the matter produced in nuclear collisions at the Relativistic Heavy Ion Collider without the assumption that it is a strongly coupled state.Comment: Final version accepted for publicatio

Fermionic Dark Matter in Radiative Inverse Seesaw Model with U(1)_{B-L}

We construct a radiative inverse seesaw model with local B-L symmetry, and investigate the flavor structure of the lepton sector and the fermionic Dark Matter. Neutrino masses are radiatively generated through a kind of inverse seesaw framework. The PMNS matrix is derived from each mixing matrix of the neutrino and charged lepton sector with large Dirac CP phase. We show that the annihilation processes via the interactions with Higgses which are independent on the lepton flavor violation, have to be dominant in order to satisfy the observed relic abundance by WMAP. The new interactions with Higgses allow us to be consistent with the direct detection result reported by XENON100, and it is possible to verify the model by the exposure of XENON100 (2012).Comment: 15 pages, 1 table, 5 figures; version accepted for publication in Physical Review

Dielectric responses of the layered cobalt oxysulfide Sr_2Cu_2CoO_2S_2 with CoO_2 square-planes

We have studied the dielectric responses of the layered cobalt oxysulfide Sr$_2$Cu$_2$CoO$_2$S$_2$ with the CoO$_2$ square-planes. With decreasing temperature below the N\'eel temperature, the resistivity increases like a semiconductor, and the thermopower decreases like a metal. The dielectric constant is highly dependent on temperature, and the dielectric relaxation is systematically changed with temperature, which is strongly correlated to the magnetic states. These behaviors suggest that carriers distributed homogeneously in the paramagnetic state at high temperatures are expelled from the antiferromagnetically ordered spin domain below the N\'eel temperature.Comment: 3 pages, 4 eps figures, to be published in J. Appl. Phy

Bi-stability of mixed states in neural network storing hierarchical patterns

We discuss the properties of equilibrium states in an autoassociative memory model storing hierarchically correlated patterns (hereafter, hierarchical patterns). We will show that symmetric mixed states (hereafter, mixed states) are bi-stable on the associative memory model storing the hierarchical patterns in a region of the ferromagnetic phase. This means that the first-order transition occurs in this ferromagnetic phase. We treat these contents with a statistical mechanical method (SCSNA) and by computer simulation. Finally, we discuss a physiological implication of this model. Sugase et al. analyzed the time-course of the information carried by the firing of face-responsive neurons in the inferior temporal cortex. We also discuss the relation between the theoretical results and the physiological experiments of Sugase et al.Comment: 18 pages, 6 figure

The light Higgs in supersymmetric models with Higgs triplets

In supersymmetric models the presence of Higgs triplets introduce new quartic interactions for the doublets that may raise the mass of the lightest CP-even field up to 205 GeV. We show that the complete effect of the triplets can be understood by decoupling them from the minimal sector and then analyzing the vacuum and the spectrum of the two-Higgs doublet model that results. We find that the maximum value of m_h is only achieved in a very definite region of the parameter space. In this region, however, radiative corrections decrease the bound to 190 GeV.Comment: 10 pages, 1 figur

The minimal B-L model naturally realized at TeV scale

In a previous paper, we have proposed the minimal B-L extended standard model as a phenomenologically viable model that realizes the Coleman-Weinberg-type breaking of the electroweak symmetry. Assuming the classical conformal invariance and stability up to the Planck scale, we will show in this paper that the model naturally predicts TeV scale B-L breaking as well as a light standard-model singlet Higgs boson and light right-handed neutrinos around the same energy scale. We also study phenomenology and detectability of the model at the Large Hadron Collider (LHC) and the International Linear Collider (ILC).Comment: 24pages, 8figure

Modelling clumpy PDRs in 3D - Understanding the Orion Bar stratification

Context. Models of photon-dominated regions (PDRs) still fail to fully reproduce some of the observed properties, in particular the combination of the intensities of different PDR cooling lines together with the chemical stratification, as observed e.g. for the Orion Bar PDR. Aims. We aim to construct a numerical PDR model, KOSMA-\tau 3D, to simulate full spectral cubes of line emission from arbitrary PDRs in three dimensions (3D). The model is to reproduce the intensity of the main cooling lines from the Orion Bar PDR and the observed layered structure of the different transitions. Methods. We build up a 3D compound, made of voxels ("3D pixels") that contain a discrete mass distribution of spherical "clumpy" structures, approximating the fractal ISM. To analyse each individual clump the new code is combined with the KOSMA-\tau PDR model. Probabilistic algorithms are used to calculate the local FUV flux for each voxel as well as the voxel-averaged line emissivities and optical depths, based on the properties of the individual clumps. Finally, the computation of the radiative transfer through the compound provides full spectral cubes. To test the new model we try to simulate the structure of the Orion Bar PDR and compare the results to observations from HIFI/Herschel and from the Caltech Submillimetre Observatory (CSO). In this context new Herschel data from the HEXOS guaranteed-time key program is presented. Results. Our model is able to reproduce the line integrated intensities within a factor 2.5 and the observed stratification pattern within 0.016 pc for the [Cii] 158 \mu m and different 12/13 CO and HCO+ transitions, based on the representation of the Orion Bar PDR by a clumpy edge-on cavity wall. In the cavity wall, a large fraction of the total mass needs to be contained in clumps. The mass of the interclump medium is constrained by the FUV penetration. Furthermore, ...Comment: Major changes compared to v1. Also several references have been adde