40 research outputs found
AdS4 black holes from M-theory
We consider the BPS conditions of eleven dimensional supergravity, restricted
to an appropriate ansatz for black holes in four non-compact directions.
Assuming the internal directions to be described by a circle fibration over a
K\"ahler manifold and considering the case where the complex structure moduli
are frozen, we recast the resulting flow equations in terms of polyforms on
this manifold. The result is a set of equations that are in direct
correspondence with those of gauged supergravity models in four dimensions
consistent with our simplifying assumptions. In view of this correspondence
even for internal manifolds that do not correspond to known consistent
truncations, we comment on the possibility of obtaining gauged supergravities
from reductions on K\"ahler manifolds.Comment: 32 pages, v2: references addes, typos correcte
non-BPS walls of marginal stability
We explore the properties of non-BPS multi-centre extremal black holes in
ungauged N=2 supergravity coupled to n_v vector multiplets, as described by
solutions to the composite non-BPS linear system. After setting up an explicit
description that allows for arbitrary non-BPS charges to be realised at each
centre, we study the structure of the resulting solutions. Using these results,
we prove that the binding energy of the composite is always positive and we
show explicitly the existence of walls of marginal stability for generic
choices of charges. The two-centre solutions only exist on a hypersurface of
dimension n_v+1 in moduli space, with an n_v-dimensional boundary, where the
distance between the centres diverges and the binding energy vanishes.Comment: 54 pages, 1 figur
A bubbling bolt
We present a new solvable system, solving the equations of five-dimensional
ungauged N=1 supergravity coupled to vector multiplets, that allows for
non-extremal solutions and reduces to a known system when restricted to the
floating brane Ansatz. A two-centre globally hyperbolic smooth geometry is
obtained as a solution to this system, describing a bubble linking a
Gibbons--Hawking centre to a charged bolt. However this solution turns out to
violate the BPS bound, and we show that its generalisation to an arbitrary
number of Gibbons--Hawking centres never admits a spin structure.Comment: 36 page
N=2 higher-derivative couplings from strings
We consider the Calabi-Yau reduction of the Type IIA eight derivative
one-loop stringy corrections focusing on the couplings of the four dimensional
gravity multiplet with vector multiplets and a tensor multiplet containing the
NS two-form. We obtain a variety of higher derivative invariants generalising
the one-loop topological string coupling, , controlled by the lowest order
Kahler potential and two new non-topological quantities built out of the
Calabi-Yau Riemann curvature.Comment: 43 page
Ungauging black holes and hidden supercharges
We embed the general solution for non-BPS extremal asymptotically flat static
and under-rotating black holes in abelian gauged D=4 N=2 supergravity, in the
limit where the scalar potential vanishes but the gauging does not. Using this
result, we show explicitly that some supersymmetries are preserved in the near
horizon region of all the asymptotically flat solutions above, in the gauged
theory. This reveals a deep relation between microscopic entropy counting of
extremal black holes in Minkowski and BPS black holes in AdS. Finally, we
discuss the relevance of this construction to the structure of asymptotically
AdS4 black holes, as well as the possibility of including hypermultiplets.Comment: 33 pages, 1 figure, v2: Corrections in section 5, comments added,
references update
Near-horizon analysis of D=5 BPS black holes and rings
A comprehensive analysis is presented based exclusively on near-horizon data
to determine the attractor equations and the entropy of BPS black holes and
rings in five space-time dimensions, for a Lagrangian invariant under eight
supersymmetries with higher-derivative couplings. For spinning black holes the
results only partially agree with the results of previous work, where often
additional input was used beyond the near-horizon behaviour. A number of
discrepancies remains, for example, pertaining to small black holes and to
large spinning black holes, which are related to the presence of the
higher-derivative couplings. Arguments are presented to explain some of them.
For the black rings, the analysis is intricate due to the presence of
Chern-Simons terms and due to the fact that the gauge fields are not globally
defined. The contributions from the higher-derivative couplings take a
systematic form in line with expectations based on a variety of arguments.Comment: 52 pages, 2 figures, PDFLaTeX, v2: typos corrected, version to appear
in JHE
The off-shell c-map
The off-shell version of the c-map is presented, based on a systematic
off-shell reduction from four to three space-time dimensions for supergravity
theories with eight supercharges. In the reduction, the R-symmetry group is
enhanced to local [SU(2) x SU(2)]/Z2 =SO(4) and the c-map is effected by a
parity transformation in the internal space that interchanges the two SU(2)
factors. Vector and tensor supermultiplets are each others conjugate under the
c-map and both can be dualized in three dimensions to (on-shell)
hypermultiplets. As shown in this paper the off-shell formulation indeed leads
to a clarification of many of the intricate issues that play a role in the
c-map. The results for off-shell Lagrangians quadratic in space-time
derivatives are analyzed in detail and compared to the literature. The
underlying reasons are identified why not all of the four-dimensional tensor
multiplet Lagrangians can be in the image of the c-map. The advantage of the
off-shell approach is, that it also enables a systematic analysis of theories
with higher-derivative couplings. This is demonstrated for a particular
subclass of such theories, which, under certain conditions, are consistent
under the c-map. In principle, explicit results for realistic four-dimensional
type-II string compactifications can be explored in this way.Comment: 57 page
Wilson lines for AdS_5 black strings
We describe a simple method of extending AdS_5 black string solutions of 5d
gauged supergravity in a supersymmetric way by addition of Wilson lines along a
circular direction in space. When this direction is chosen along the string,
and due to the specific form of 5d supergravity that features Chern-Simons
terms, the existence of magnetic charges automatically generates conserved
electric charges in a 5d analogue of the Witten effect. Therefore we find a
rather generic, model-independent way of adding electric charges to already
existing solutions with no backreaction from the geometry or breaking of any
symmetry. We use this method to explicitly write down more general versions of
the Benini-Bobev black strings and comment on the implications for the dual
field theory and the similarities with generalizations of the Cacciatori-Klemm
black holes in AdS_4.Comment: 13 pages; v2 improved discussion, added reference