22 research outputs found
Reaction processes between tholeiitic melt and residual peridotite in the uppermost mantle: an experimental study at 0.8 GPa
ISSN:0022-3530ISSN:1460-241
Black Hole Deconstruction
A D4-D0 black hole can be deconstructed into a bound state of D0 branes with
a D6-anti-D6 pair containing worldvolume fluxes. The exact spacetime solution
is known and resembles a D0 accretion disk surrounding a D6-anti-D6 core. We
find a scaling limit in which the disk and core drop inside an AdS_2 throat.
Crossing this AdS_2 throat and the D0 accretion disk into the core, we find a
second scaling region describing the D6-anti-D6 pair. It is shown that the
M-theory lift of this region is AdS_3 x S^2. Surprisingly, time translations in
the far asymptotic region reduce to global, rather than Poincare, time
translations in this core AdS_3. We further find that the quantum mechanical
ground state degeneracy reproduces the Bekenstein-Hawking entropy-area law.Comment: 11 page
BPS dyons and Hesse flow
We revisit BPS solutions to classical N=2 low energy effective gauge
theories. It is shown that the BPS equations can be solved in full generality
by the introduction of a Hesse potential, a symplectic analog of the
holomorphic prepotential. We explain how for non-spherically symmetric,
non-mutually local solutions, the notion of attractor flow generalizes to
gradient flow with respect to the Hesse potential. Furthermore we show that in
general there is a non-trivial magnetic complement to this flow equation that
is sourced by the momentum current in the solution.Comment: 25 pages, references adde
Black Holes as Effective Geometries
Gravitational entropy arises in string theory via coarse graining over an
underlying space of microstates. In this review we would like to address the
question of how the classical black hole geometry itself arises as an effective
or approximate description of a pure state, in a closed string theory, which
semiclassical observers are unable to distinguish from the "naive" geometry. In
cases with enough supersymmetry it has been possible to explicitly construct
these microstates in spacetime, and understand how coarse-graining of
non-singular, horizon-free objects can lead to an effective description as an
extremal black hole. We discuss how these results arise for examples in Type II
string theory on AdS_5 x S^5 and on AdS_3 x S^3 x T^4 that preserve 16 and 8
supercharges respectively. For such a picture of black holes as effective
geometries to extend to cases with finite horizon area the scale of quantum
effects in gravity would have to extend well beyond the vicinity of the
singularities in the effective theory. By studying examples in M-theory on
AdS_3 x S^2 x CY that preserve 4 supersymmetries we show how this can happen.Comment: Review based on lectures of JdB at CERN RTN Winter School and of VB
at PIMS Summer School. 68 pages. Added reference
Homogeneous nonrelativistic geometries as coset spaces
We generalize the coset procedure of homogeneous spacetimes in (pseudo-) Riemannian geometry to non-Lorentzian geometries. These are manifolds endowed with nowhere vanishing invertible vielbeins that transform under local non-Lorentzian tangent space transformations. In particular we focus on nonrelativistic symmetry algebras that give rise to (torsional) Newton-Cartan geometries, for which we demonstrate how the Newton-Cartan metric complex is determined by degenerate co- and contravariant symmetric bilinear forms on the coset. In specific cases we also show the connection of the resulting nonrelativistic coset spacetimes to pseudo-Riemannian cosets via Inonu-Wigner contraction of relativistic algebras as well as null reduction. Our construction is of use for example when considering limits of the AdS/CFT correspondence in which nonrelativistic spacetimes appear as gravitational backgrounds for nonrelativistic string or gravity theories
BPS Spectrum, Indices and Wall Crossing in N=4 Supersymmetric Yang-Mills Theories
BPS states in N=4 supersymmetric SU(N) gauge theories in four dimensions can
be represented as planar string networks with ends lying on D3-branes. We
introduce several protected indices which capture information on the spectrum
and various quantum numbers of these states, give their wall crossing formula
and describe how using the wall crossing formula we can compute all the indices
at all points in the moduli space.Comment: LaTeX file, 33 pages, 15 figure
The Hesse potential, the c-map and black hole solutions
We present a new formulation of the local c-map, which makes use of the real
formulation of special Kahler geometry and the associated Hesse potential. As
an application we use the temporal version of the c-map to derive the black
hole attractor equations from geometric properties of the scalar manifold, and
we construct various stationary solutions for four-dimensional vector
multiplets by lifting instanton solutions of the time-reduced theory.Comment: 76 pages. Second revised version: substantial extension. Further
references added and discussion extended. Construction of axion-free non-BPS
extremal solutions for a class of non-homogeneous target spaces added.
Accepted for publication in JHE
Strolling along gauge theory vacua
We consider classical, pure Yang-Mills theory in a box. We show how a set of
static electric fields that solve the theory in an adiabatic limit correspond
to geodesic motion on the space of vacua, equipped with a particular Riemannian
metric that we identify. The vacua are generated by spontaneously broken global
gauge symmetries, leading to an infinite number of conserved momenta of the
geodesic motion. We show that these correspond to the soft multipole charges of
Yang-Mills theory.Comment: 46 pages, 1 figure, Published versio
Quantizing N=2 Multicenter Solutions
N=2 supergravity in four dimensions, or equivalently N=1 supergravity in five
dimensions, has an interesting set of BPS solutions that each correspond to a
number of charged centers. This set contains black holes, black rings and their
bound states, as well as many smooth solutions. Moduli spaces of such solutions
carry a natural symplectic form which we determine, and which allows us to
study their quantization. By counting the resulting wavefunctions we come to an
independent derivation of some of the wall-crossing formulae. Knowledge of the
explicit form of these wavefunctions allows us to find quantum resolutions to
some apparent classical paradoxes such as solutions with barely bound centers
and those with an infinitely deep throat. We show that quantum effects seem to
cap off the throat at a finite depth and we give an estimate for the
corresponding mass gap in the dual CFT. This is an interesting example of a
system where quantum effects cannot be neglected at macroscopic scales even
though the curvature is everywhere small.Comment: 49 pages + appendice