The ground-state of General Relativity, Topological Theories and Dark Matter

We suggest a limit of Einstein equations incorporating the state $g_{\mu\nu}=0$ as a solution. The large scale behavior of this theory has interesting properties. For a spherical source, the velocity profile for circular motions is of the form observed in galaxies (approximately flat). For FRW cosmologies, the Friedman equation contains an additional contribution in the matter sector.Comment: More clarifications on the interpretation of the limits. Shorter version. 4 pages, two column, no figure

Growth of aerobic and anaerobic bacteria in agar subjected to freezing and diurnal freezing and thawing

Aerobic and anaerobic bacteria growth in agar after freezing and diurnal freezing and thawin

Realistic Neutrino Opacities for Supernova Simulations With Correlations and Weak Magnetism

Advances in neutrino transport allow realistic neutrino interactions to be incorporated into supernova simulations. We add tensor couplings to relativistic RPA calculations of neutrino opacities. Our results reproduce free-space neutrino-nucleon cross sections at low density, including weak magnetism and recoil corrections. In addition, our opacities are thermodynamically consistent with relativistic mean field equations of state. We find antineutrino mean free paths that are considerably larger then those for neutrinos. This difference depends little on density. In a supernova, this difference could lead to an average energy of $\bar\nu_\mu$ that is larger than that for $\nu_\mu$ by an amount that is comparable to the energy difference between $\nu_\mu$ and $\bar\nu_e$Comment: 15 pages, 10 figures, submitted to PRC, minor changes to figs. (9,10

Bubbles Unbound: Bubbles of Nothing Without Kaluza-Klein

I present analytic time symmetric initial data for five dimensions describing ``bubbles of nothing'' which are asymptotically flat in the higher dimensional sense, i.e. there is no Kaluza-Klein circle asymptotically. The mass and size of these bubbles may be chosen arbitrarily and in particular the solutions contain bubbles of any size which are arbitrarily light. This suggests the solutions may be important phenomenologically and in particular I show that at low energy there are bubbles which expand outwards, suggesting a new possible instability in higher dimensions. Further, one may find bubbles of any size where the only region of high curvature is confined to an arbitrarily small volume.Comment: 27 pages, 2 figures, v2: minor changes, published versio

A Correspondence Principle for Black Holes and Strings

For most black holes in string theory, the Schwarzschild radius in string units decreases as the string coupling is reduced. We formulate a correspondence principle, which states that (i) when the size of the horizon drops below the size of a string, the typical black hole state becomes a typical state of strings and D-branes with the same charges, and (ii) the mass does not change abruptly during the transition. This provides a statistical interpretation of black hole entropy. This approach does not yield the numerical coefficient, but gives the correct dependence on mass and charge in a wide range of cases, including neutral black holes.Comment: 24 pages, one typo correcte

NK cells as effectors of acquired immune responses: effector CD4+ T cell-dependent activation of NK cells following vaccination.

We characterized vaccine-induced cellular responses to rabies virus in naive adult volunteers. Contrary to current paradigms, we observed potent and prolonged in vitro NK cell cytokine production and degranulation responses after restimulation of PBMCs with inactivated rabies virus in vaccinated, but not in unvaccinated, individuals. This "recall" NK cell response was absolutely dependent on Ag-specific IL-2 from CD45RO(+) CD4(+) T cells as well as IL-12 and IL-18 from accessory cells. Importantly, NK cells represented over 70% of all IFN-gamma-secreting and degranulating cells in the first 12-18 h after virus rechallenge indicating they may be required for rapid control of infection after vaccination. Activation of NK cells may be a critical function of IL-2-secreting effector memory T cells. Although IL-2-dependent postvaccination NK cell activation has been reported previously, this is the first time the magnitude of this effect and its contribution to the overall vaccine-induced response has been appreciated and the mechanisms of NK activation postvaccination have been elucidated. Our data will allow standard protocols for evaluating vaccine-induced immunity to be adapted to assess NK cell effector responses

When Black Holes Meet Kaluza-Klein Bubbles

We explore the physical consequences of a recently discovered class of exact solutions to five dimensional Kaluza-Klein theory. We find a number of surprising features including: (1) In the presence of a Kaluza-Klein bubble, there are arbitrarily large black holes with topology S^3. (2) In the presence of a black hole or a black string, there are expanding bubbles (with de Sitter geometry) which never reach null infinity. (3) A bubble can hold two black holes of arbitrary size in static equilibrium. In particular, two large black holes can be close together without merging to form a single black hole.Comment: 23 pages, 5 figures, v2: few comments on stability modifie

Dirac Hartree-Fock for Finite Nuclei Employing realistic Forces

We discuss two different approximation schemes for the self-consistent solution of the {\it relativistic} Brueckner-Hartree-Fock equation for finite nuclei. In the first scheme, the Dirac effects are deduced from corresponding nuclear matter calculations, whereas in the second approach the local-density approximation is used to account for the effects of correlations. The results obtained by the two methods are very similar. Employing a realistic one-boson-exchange potential (Bonn~A), the predictions for energies and radii of $^{16}$O and $^{40}$Ca come out in substantially better agreement with experiment as compared to non-relativistic approaches. As a by-product of our study, it turns out that the Fock exchange-terms, ignored in a previous investigation, are not negligible.Comment:

Probing the Continuum Limit in Non-Compact QED: New Results on Large Lattices

We present new Monte Carlo results in non-compact lattice QED with staggered fermions down to m_0 = 0.005. This extends our previous investigations on the nature of the continuum limit of QED.Comment: 7 pages, uuencoded compressed PostScript, also available at ftp://ftp.zib-berlin.de/pub/zib-publications/Reports/SC-94-31.ps.

Distributed Systems of Intersecting Branes at Arbitrary Angles

A `reduced' action formulation for a general class of the supergravity solutions, corresponding to the `marginally' bound `distributed' systems of various types of branes at arbitrary angles, is developed. It turns out that all the information regarding the classical features of such solutions is encoded in a first order Lagrangian (the `reduced' Lagrangian) corresponding to the desired geometry of branes. The marginal solution for a system of $N$ such distributions (for various distribution functions) span an $N$ dimensional submanifold of the fields' configuration (target) space, parametrised by a set of $N$ independent harmonic functions on the transverse space. This submanifold, which we call it as the `$H$-surface', is a null surface with respect to a metric on the configuration space, which is defined by the reduced Lagrangian. The equations of motion then transform to a set of equations describing the embedding of a null geodesic surface in this space, which is identified as the $H$-surface. Using these facts, we present a very simple derivation of the conventional orthogonal solutions together with their intersection rules. Then a new solution for a (distributed) pair of $p$-branes at SU(2) angles in $D$ dimensions is derived.Comment: Latex file, 58 pages, no figures, 5 tables, This revision contains some minor changes of the original version including those of the title, abstract and referrences. Some comments are adde