Short Distance Repulsion Among Baryons

We review recent investigations on the short distance behaviors of potentials among baryons, which are formulated through the Nambu-Bethe-Salpeter (NBS) wave function. After explaining the method to define the potentials, we analyze the short distance behavior of the NBS wave functions and the corresponding potentials by combining the operator product expansion and a renormalization group analysis in the perturbation theory of QCD. These analytic results are compared with numerical results obtained in lattice QCD simulations.Comment: 16 pages, late

Monoidal Hom-Hopf algebras

Hom-structures (Lie algebras, algebras, coalgebras, Hopf algebras) have been investigated in the literature recently. We study Hom-structures from the point of view of monoidal categories; in particular, we introduce a symmetric monoidal category such that Hom-algebras coincide with algebras in this monoidal category, and similar properties for coalgebras, Hopf algebras and Lie algebras.Comment: 25 pages; extended version: compared to the version that appeared in Comm. Algebra, the Section Preliminary Results and Remarks 5.1 and 6.1 have been adde

Monolithic Ge:Ga Detector Development for SAFARI

We describe the current status and the prospect for the development of monolithic Ge:Ga array detector for SAFARI. Our goal is to develop a 64x64 array for the 45 -- 110 um band, on the basis of existing technologies to make 3x20 monolithic arrays for the AKARI satellite. For the AKARI detector we have achieved a responsivity of 10 A/W and a read-out noise limited NEP (noise equivalent power) of 10^-17 W/rHz. We plan to develop the detector for SAFARI with technical improvements; significantly reduced read-out noise with newly developed cold read-out electronics, mitigated spectral fringes as well as optical cross-talks with a multi-layer antireflection coat. Since most of the elemental technologies to fabricate the detector are flight-proven, high technical readiness levels (TRLs) should be achieved for fabricating the detector with the above mentioned technical demonstrations. We demonstrate some of these elemental technologies showing results of measurements for test coatings and prototype arrays.Comment: To appear in Proc. Workshop "The Space Infrared Telescope for Cosmology & Astrophysics: Revealing the Origins of Planets and Galaxies". Eds. A.M. Heras, B. Swinyard, K. Isaak, and J.R. Goicoeche

Crystal nucleation mechanism in melts of short polymer chains under quiescent conditions and under shear flow

We present a molecular dynamics simulation study of crystal nucleation from undercooled melts of n-alkanes, and we identify the molecular mechanism of homogeneous crystal nucleation under quiescent conditions and under shear flow. We compare results for n-eicosane(C20) and n-pentacontahectane(C150), i.e. one system below the entanglement length and one above. Under quiescent conditions, we observe that entanglement does not have an effect on the nucleation mechanism. For both chain lengths, the chains first align and then straighten locally. Then the local density increases and finally positional ordering sets in. At low shear rates the nucleation mechanism is the same as under quiescent conditions, while at high shear rates the chains align and straighten at the same time. We report on the effects of shear rate and temperature on the nucleation rates and estimate the critical shear rates, beyond which the nucleation rates increase with the shear rate. We show that the viscosity of the system is not affected by the crystalline nuclei.Comment: 9 page

Neutrino-less Double Electron Capture - a tool to research for Majorana neutrinos

The possibility to observe the neutrino-less double $\beta$ decay and thus to prove the Majorana nature of neutrino as well as provide a sensitive measure of its mass is a major challenge of to-day's neutrino physics. As an attractive alternative we propose to study the inverse process, the radiative neutrino-less double electron capture $0 \nu 2EC$. The associated monoenergetic photon provides a convenient experimental signature. Other advantages include the favourable ratio of the $0 \nu 2EC$ to the competing $2\nu 2EC$ capture rates and, very importantly, the existence of coincidence trigger to suppress the random background. These advantages partly offset the expected longer lifetimes. Rates for the $0\gamma 2EC$ process are calculated. High Z atoms are strongly favoured. A resonance enhancement of the capture rates is predicted at energy release comparable to the $2P-1S$ atomic level difference. The resonance conditions are likely to be met for decays to excited states in final nuclei. Candidates for such studies are considered. The experimental feasibility is estimated and found highly encouraging.Comment: New figure added, table updated, physical background discusse

The topological glass in ring polymers

We study the dynamics of concentrated, long, semi-flexible, unknotted and unlinked ring polymers embedded in a gel by Monte Carlo simulation of a coarse-grained model. This involves the ansatz that the rings compactify into a duplex structure where they can be modelled as linear polymers. The classical polymer glass transition involves a rapid loss of microscopic freedom within the polymer molecule as the temperature is reduced toward Tg. Here we are interested in temperatures well above Tg where the polymers retain high microscopic mobility. We analyse the slowing of stress relaxation originating from inter-ring penetrations (threadings). For long polymers an extended network of quasi-topological penetrations forms. The longest relaxation time appears to depend exponentially on the ring polymer contour length, reminiscent of the usual exponential slowing (e.g., with temperature) in classical glasses. Finally, we discuss how this represents a universality class for glassy dynamics

On U_q(SU(2))-symmetric Driven Diffusion

We study analytically a model where particles with a hard-core repulsion diffuse on a finite one-dimensional lattice with space-dependent, asymmetric hopping rates. The system dynamics are given by the \mbox{U$_{q}$[SU(2)]}-symmetric Hamiltonian of a generalized anisotropic Heisenberg antiferromagnet. Exploiting this symmetry we derive exact expressions for various correlation functions. We discuss the density profile and the two-point function and compute the correlation length $\xi_s$ as well as the correlation time $\xi_t$. The dynamics of the density and the correlations are shown to be governed by the energy gaps of a one-particle system. For large systems $\xi_s$ and $\xi_t$ depend only on the asymmetry. For small asymmetry one finds $\xi_t \sim \xi_s^2$ indicating a dynamical exponent $z=2$ as for symmetric diffusion.Comment: 10 pages, LATE