7,915 research outputs found
Open String Attractors
We present a simple example of a supersymmetric attractor mechanism in the
purely open string context of D-branes embedded in curved space-time. Our
example involves a class of D3-branes embedded in the 2-charge D1-D5 background
of type IIB whose worldvolume contains a 2-sphere. Turning on worldvolume
fluxes, these branes carry induced (p,q) string charges. Supersymmetric
configurations display a flow of the open string moduli towards an attractor
solution independent of their asymptotics. The equations governing this
mechanism closely resemble the attractor flow equations for supersymmetric
black holes in closed string theory. The BPS equations take the form of a
gradient flow and describe worldvolume solitons interpolating between an AdS_2
geometry where the two-sphere has collapsed, and an attractor solution with
AdS_2 x S^2 geometry. In these limiting solutions, the preserved supersymmetry
is enhanced from 4 to 8 supercharges. We also discuss the interpretation of our
solutions as intersecting brane configurations placed in the D1-D5 background,
as well as the S-duality transformation to the F1-NS5 background.Comment: 37 pages, 6 figures. v2: small corrections, figure and references
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Multiple Single-Centered Attractors
In this paper we study spherically symmetric single-centered attractors in
N=2 supergravity in four dimensions. The attractor points are obtained by
extremising the effective black hole potential in the moduli space. Using the
4D-5D correspondence of critical points of the effective black hole potential
we argue the existence of multiple attractors in four dimensions and explicitly
construct a pair of multiple solutions in a simple two parameter model. We
further obtain explicit examples of two distinct non-supersymmetric attractors
in type IIA string theory compactified on K3 X T2 carrying D0-D4-D6 charges. We
compute the entropy of these attractors and analyse their stability in detail.Comment: Modifications in Section 3. Some incorrect results are removed and
the section is rewritte
Flux Vacua Attractors in Type II on SU(3)xSU(3) Structure
We summarize and extend our work on flux vacua attractors in generalized
compactifications. After reviewing the attractor equations for the heterotic
string on SU(3) structure manifolds, we study attractors for N=1 vacua in type
IIA/B on SU(3)xSU(3) structure spaces. In the case of vanishing RR flux, we
find attractor equations that encode Minkowski vacua only (and which correct a
previous normalization error). In addition to our previous considerations, here
we also discuss the case of nonzero RR flux and the possibility of attractors
for AdS vacua.Comment: 10 pages, contribution to the proceedings of the 4th RTN workshop
"Forces Universe", Varna, September 200
String attractors and combinatorics on words
The notion of string attractor has recently been introduced in [Prezza, 2017] and studied in [Kempa and Prezza, 2018] to provide a unifying framework for known dictionary-based compressors. A string attractor for a word w = w[1]w[2] · · · w[n] is a subset Γ of the positions 1, . . ., n, such that all distinct factors of w have an occurrence crossing at least one of the elements of Γ. While finding the smallest string attractor for a word is a NP-complete problem, it has been proved in [Kempa and Prezza, 2018] that dictionary compressors can be interpreted as algorithms approximating the smallest string attractor for a given word. In this paper we explore the notion of string attractor from a combinatorial point of view, by focusing on several families of finite words. The results presented in the paper suggest that the notion of string attractor can be used to define new tools to investigate combinatorial properties of the words
Non-Supersymmetric Attractors in String Theory
We find examples of non-supersymmetric attractors in Type II string theory
compactified on a Calabi Yau three-fold. For a non-supersymmetric attractor the
fixed values to which the moduli are drawn at the horizon must minimise an
effective potential. For Type IIA at large volume, we consider a configuration
carrying D0, D2, D4 and D6 brane charge. When the D6 brane charge is zero, we
find for some range of the other charges, that a non-supersymmetric attractor
solution exists. When the D6 brane charge is non-zero, we find for some range
of charges, a supersymmetry breaking extremum of the effective potential.
Closer examination reveals though that it is not a minimum of the effective
potential and hence the corresponding black hole solution is not an attractor.
Away from large volume, we consider the specific case of the quintic in CP^4.
Working in the mirror IIB description we find non-supersymmetric attractors
near the Gepner point.Comment: Added a few clarification
Non-BPS Attractors in 5d and 6d Extended Supergravity
We connect the attractor equations of a certain class of N=2, d=5
supergravities with their (1,0), d=6 counterparts, by relating the moduli space
of non-BPS d=5 black hole/black string attractors to the moduli space of
extremal dyonic black string d=6 non-BPS attractors. For d = 5 real special
symmetric spaces and for N = 4,6,8 theories, we explicitly compute the flat
directions of the black object potential corresponding to vanishing eigenvalues
of its Hessian matrix. In the case N = 4, we study the relation to the (2,0),
d=6 theory. We finally describe the embedding of the N=2, d=5 magic models in
N=8, d=5 supergravity as well as the interconnection among the corresponding
charge orbits.Comment: 1+27 page
String attractors of Rote sequences
In this paper, we describe minimal string attractors (of size two) of
pseudopalindromic prefixes of standard complementary-symmetric Rote sequences.
Such a class of Rote sequences forms a subclass of binary generalized
pseudostandard sequences, i.e., of sequences obtained when iterating
palindromic and antipalindromic closures. When iterating only palindromic
closure, palindromic prefixes of standard Sturmian sequences are obtained and
their string attractors are of size two. However, already when iterating only
antipalindromic closure, antipalindromic prefixes of binary pseudostandard
sequences are obtained and we prove that the minimal string attractors are of
size three in this case. We conjecture that the pseudopalindromic prefixes of
any binary generalized pseudostandard sequence have a minimal string attractor
of size at most four
Instanton Corrected Non-Supersymmetric Attractors
We discuss non-supersymmetric attractors with an instanton correction in Type
IIA string theory compactified on a Calabi-Yau three-fold at large volume. For
a stable non-supersymmetric black hole, the attractor point must minimize the
effective black hole potential. We study the supersymmetric as well as
non-supersymmetric attractors for the D0-D4 system with instanton corrections.
We show that in simple models, like the STU model, the flat directions of the
mass matrix can be lifted by a suitable choice of the instanton parameters.Comment: Minor modifications, Corrected typos, 38 pages, 1 figur
Black Hole Attractors and the Topological String
A simple relationship of the form Z_BH = |Z_top|^2 is conjectured, where Z_BH
is a supersymmetric partition function for a four-dimensional BPS black hole in
a Calabi-Yau compactification of Type II superstring theory and Z_top is a
second-quantized topological string partition function evaluated at the
attractor point in moduli space associated to the black hole charges. Evidence
for the conjecture in a perturbation expansion about large graviphoton charge
is given. The microcanonical ensemble of BPS black holes can be viewed as the
Wigner function associated to the wavefunction defined by the topological
string partition function.Comment: 32 pages, harvma
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