8,495 research outputs found
The ground-state of General Relativity, Topological Theories and Dark Matter
We suggest a limit of Einstein equations incorporating the state
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 that is larger than
that for by an amount that is comparable to the energy difference
between and 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 O and 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 such
distributions (for various distribution functions) span an dimensional
submanifold of the fields' configuration (target) space, parametrised by a set
of independent harmonic functions on the transverse space. This
submanifold, which we call it as the `-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 -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 -branes
at SU(2) angles in 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
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