70 research outputs found
Mellin Bootstrap for Scalars in Generic Dimension
We use the recently developed framework of the Mellin bootstrap to study
perturbatively free scalar CFTs in arbitrary dimensions. This approach uses the
crossing-symmetric Mellin space formulation of correlation functions to
generate algebraic bootstrap equations by demanding that only physical
operators contribute to the OPE. We find that there are no perturbatively
interacting CFTs with only fundamental scalars in dimensions (to at least
second order in the perturbation). Our results can be seen as a modest step
towards understanding the space of interacting CFTs in and are consistent
with the intuition that no such CFTs exist.Comment: 11 pages + appendices. v2: references added, few minor revisions;
published versio
Multi-centered D1-D5 solutions at finite B-moduli
We study the fate of two-centered D1-D5 systems on T^4 away from the singular
supergravity point in the moduli space. We do this by considering a background
D1-D5 black hole with a self-dual B-field moduli turned on and treating the
second center in the probe limit in this background. We find that in general
marginal bound states at zero moduli become metastable at finite B-moduli,
demonstrating a breaking of supersymmetry. However, we also find evidence that
when the charges of both centers are comparable, the effects of supersymmetry
breaking become negligible. We show that this effect is independent of string
coupling and thus it should be possible to reproduce this in the CFT at weak
coupling. We comment on the implications for the fuzzball proposal.Comment: 19 pages + appendices, 14 figures; v2: added important remark in
example in introduction, rewrote first paragraph in sect 3.2 for clarity,
other misc. small edits; as accepted for publication in JHE
Structure of Six-Dimensional Microstate Geometries
We investigate the structure of smooth and horizonless microstate geometries
in six dimensions, in the spirit of the five-dimensional analysis of Gibbons
and Warner [arXiv:1305.0957]. In six dimensions, which is the natural setting
for horizonless geometries with the charges of the D1-D5-P black hole, the
natural black objects are strings and there are no Chern-Simons terms for the
tensor gauge fields. However, we still find that the same reasoning applies: in
absence of horizons, there can be no smooth stationary solutions without
non-trivial topology. We use topological arguments to describe the Smarr
formula in various examples: the uplift of the five-dimensional minimal
supergravity microstates to six dimensions, the two-charge D1-D5 microstates,
and the non-extremal JMaRT solution. We also discuss D1-D5-P superstrata and
confirm that the Smarr formula gives the same result as for the D1-D5
supertubes which are topologically equivalent.Comment: 29 pages, v2: references added, published versio
Higher Derivative Corrections and Central Charges from Wrapped M5-branes
We compute four-derivative corrections to the AdS supergravity actions
arising from the near-horizon geometry of N M5-branes wrapped on either one or
two Riemann surfaces. This setup features the novel presence of both gauged
isometries as well as nontrivial hypermultiplets. We argue that the 5d
Chern-Simons terms receive not only higher-derivative corrections but also
contributions from Killing vector parameters, which we find must also be
corrected. We check the central charges found by our supergravity methods
against the dual field theory results and find perfect agreement at leading and
subleading order in N. Along the way, we find higher derivative corrections to
general AdS_5 and AdS_3x\Sigma_g geometries.Comment: 32 pages + 16 pages appendice
Holographic Flavored Quark-Gluon Plasmas
Holography provides a novel method to study the physics of Quark Gluon
Plasmas, complementary to the ordinary field theory and lattice approaches. In
this context, we analyze the informations that can be obtained for strongly
coupled Plasmas containing dynamical flavors, also in the presence of a finite
baryon chemical potential. In particular, we discuss the jet quenching and the
hydrodynamic transport coefficients.Comment: 10 pages. Contribution to the proceedings of the workshop "The many
faces of QCD", Ghent (Belgium), November 1-5 201
Black Hole Multipoles in Higher-Derivative Gravity
We consider a broad family of higher-derivative extensions of
four-dimensional Einstein gravity and study the multipole moments of rotating
black holes therein. We carefully show that the various definitions of
multipoles carry over from general relativity, and compute these multipoles for
higher-derivative Kerr using the ACMC expansion formalism. We obtain the mass
and current multipoles as a series expansions in the
dimensionless spin; in some cases we are able to resum these series into
closed-form expressions. Moreover, we observe the existence of intriguing
relations between the corrections to the parity-odd multipoles
and that break equatorial symmetry, and the parity-preserving
corrections that only modify and . Further, we comment on
the higher-derivative corrections to multipole ratios for Kerr, and we discuss
the phenomenological implications of the corrections to the multipole moments
for current and future gravitational wave experiments.Comment: 31 pages + Appendix, 13 figures, Mathematica notebook with all
expansions used in the pape
Black Hole Photon Rings Beyond General Relativity
We investigate whether photon ring observations in black hole imaging are
able to distinguish between the Kerr black hole in general relativity and
alternative black holes that deviate from Kerr. Certain aspects of photon rings
have been argued to be robust observables in Very-Long-Baseline Interferometry
(VLBI) black hole observations which carry imprints of the underlying
spacetime. The photon ring shape, as well as its Lyapunov exponent (which
encodes the narrowing of successive photon subrings), are detailed probes of
the underlying geometry; measurements thereof have been argued to provide a
strong null test of general relativity and the Kerr metric. However, a more
complicated question is whether such observations of the photon ring properties
can distinguish between Kerr and alternative black holes. We provide a first
answer to this question by calculating photon rings of the Johannsen,
Rasheed-Larsen, and Manko-Novikov black holes. We find that large deviations
from Kerr and large observer inclinations are needed to obtain measurable
differences in the photon ring shape. In other words, the Kerr photon ring
shape appears to be the universal shape even for deviating black holes at low
inclinations. On the other hand, the Lyapunov exponent shows more marked
variations for deviations from the Kerr metric. Our analysis lays out the
groundwork to determine deviations from the Kerr spacetime in photon rings that
are potentially detectable by future observing missions.Comment: 31 pages + appendices; 20 figure
Classifying supersymmetric solutions in 3D maximal supergravity
The work of MS was supported in part by Grant-in-Aid for Young Scientists (B) 24740159 from the Japan Society for the Promotion of Science (JSPS) 10.13039/501100001691. This work is part of the research programme of the Foundation for Fundamental Research on Matter (FOM) 10.13039/ 501100003404, which is part of the Netherlands Organization for Scientific Research (NWO).The work of MS was supported in part by Grant-in-Aid for Young Scientists (B) 24740159 from the Japan Society for the Promotion of Science (JSPS) 10.13039/501100001691. This work is part of the research programme of the Foundation for Fundamental Research on Matter (FOM) 10.13039/ 501100003404, which is part of the Netherlands Organization for Scientific Research (NWO).The work of MS was supported in
part by Grant-in-Aid for Young Scientists (B) 24740159 from the Japan Society for the
Promotion of Science (JSPS) 10.13039/501100001691. This work is part of the research
programme of the Foundation for Fundamental Research on Matter (FOM) 10.13039/
501100003404, which is part of the Netherlands Organization for Scientific Research (NWO
D3-D7 Quark-Gluon Plasmas at Finite Baryon Density
We present the string dual to SU(Nc) N=4 SYM, coupled to Nf massless
fundamental flavors, at finite temperature and baryon density. The solution is
determined by two dimensionless parameters, both depending on the 't Hooft
coupling at the scale set by the temperature T:
, weighting the backreaction of the flavor
fields and , where is the
baryon density. For small values of these two parameters the solution is given
analytically up to second order. We study the thermodynamics of the system in
the canonical and grand-canonical ensembles. We then analyze the energy loss of
partons moving through the plasma, computing the jet quenching parameter and
studying its dependence on the baryon density. Finally, we analyze certain
"optical" properties of the plasma. The whole setup is generalized to non
abelian strongly coupled plasmas engineered on D3-D7 systems with D3-branes
placed at the tip of a generic singular Calabi-Yau cone. In all the cases,
fundamental matter fields are introduced by means of homogeneously smeared
D7-branes and the flavor symmetry group is thus a product of abelian factors.Comment: 27 pages; v2: 29 pages, 1 (new) figure, new section 4.4 on optical
properties, references, comments added; v3: eq. (3.19), comments and a
reference adde
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