149 research outputs found
Force-free magnetosphere attractors for near-horizon extreme and near-extreme limits of Kerr black hole
We propose a new approach to find magnetically-dominated force-free
magnetospheres around highly spinning black holes, relevant for models of
astrophysical jets. Employing the near-horizon extreme Kerr (NHEK) limit of the
Kerr black hole, any stationary, axisymmetric and regular force-free
magnetosphere reduces to the same attractor solution in the NHEK limit with
null electromagnetic field strength. We use this attractor solution as the
universal starting point for perturbing away from the NHEK region in the
extreme Kerr spacetime. We demonstrate that by going to second order in
perturbation theory, it is possible to find magnetically dominated
magnetospheres around the extreme Kerr black hole. Furthermore, we consider the
near-horizon near-extreme Kerr (near-NHEK) limit that provides access to a
different regime of highly spinning black holes. Also in this case we find a
novel force-free attractor, which can be used as the universal starting point
for a perturbative construction of force-free magnetospheres. Finally, we
discuss the relation between the NHEK and near-NHEK attractors.Comment: 5 pages, 1 figur
Moving away from the Near-Horizon Attractor of the Extreme Kerr Force-Free Magnetosphere
We consider force-free magnetospheres around the extreme Kerr black hole. In
this case there is no known exact analytic solution to force free
electrodynamics which is stationary, axisymmetric and magnetically-dominated.
However, any stationary, axisymmetric and regular force-free magnetosphere in
extreme Kerr black hole approaches the same attractor solution in the
near-horizon extreme Kerr (NHEK) limit with null electromagnetic field. We show
that by moving away from the attractor solution in the NHEK region, one finds
magnetically-dominated solutions in the extreme Kerr black hole with finite
angular momentum outflow. This result is achieved using a perturbative analysis
up to the second order.Comment: 33 pages, 2 figures; v2: matches published version in JCA
Decoupling limits of N=4 super Yang-Mills on R x S^3
We find new decoupling limits of N=4 super Yang-Mills (SYM) on R x S^3 with
gauge group SU(N). These decoupling limits lead to decoupled theories that are
much simpler than the full N=4 SYM but still contain many of its interesting
features. The decoupling limits correspond to being in a near-critical region,
near a point with zero temperature and critical chemical potentials. The new
decoupling limits are found by generalizing the limits of hep-th/0605234 to
include not only the chemical potentials for the SU(4) R-symmetry of N=4 SYM
but also the chemical potentials corresponding to the SO(4) symmetry. In the
decoupled theories it is possible to take a strong coupling limit in a
controllable manner since the full effective Hamiltonian is known. For planar
N=4 SYM on R x S^3 all the decoupled theories correspond to fully integrable
spin chains. We study the thermodynamics of the decoupled theories and find the
Hagedorn temperature for small and large values of the effective coupling. We
find an alternative formulation of the decoupling limits in the microcanonical
ensemble. This leads to a characterization of certain regimes of weakly coupled
N=4 SYM in which there are string-like states. Finally, we find a similar
decoupling limit for pure Yang-Mills theory, which for the planar limit leads
to a fully integrable decoupled theory.Comment: 48 pages, 1 figure; added references, published versio
Space/Time Noncommutativity in String Theories without Background Electric Field
The appearance of space/time non-commutativity in theories of open strings
with a constant non-diagonal background metric is considered. We show that,
even if the space-time coordinates commute, when there is a metric with a
time-space component, no electric field and the boundary condition along the
spatial direction is Dirichlet, a Moyal phase still arises in products of
vertex operators. The theory is in fact dual to the non-commutatitive open
string (NCOS) theory. The correct definition of the vertex operators for this
theory is provided. We study the system also in the presence of a field. We
consider the case in which the Dirichlet spatial direction is compactified and
analyze the effect of these background on the closed string spectrum. We then
heat up the system. We find that the Hagedorn temperature depends in a
non-extensive way on the parameters of the background and it is the same for
the closed and the open string sectors.Comment: 18 pages, JHEP styl
Thermal Giant Gravitons
We study the giant graviton solution as the AdS_5 X S^5 background is heated
up to finite temperature. The analysis employs the thermal brane probe
technique based on the blackfold approach. We focus mainly on the thermal giant
graviton corresponding to a thermal D3-brane probe wrapped on an S^3 moving on
the S^5 of the background at finite temperature. We find several interesting
new effects, including that the thermal giant graviton has a minimal possible
value for the angular momentum and correspondingly also a minimal possible
radius of the S^3. We compute the free energy of the thermal giant graviton in
the low temperature regime, which potentially could be compared to that of a
thermal state on the gauge theory side. Moreover, we analyze the space of
solutions and stability of the thermal giant graviton and find that, in
parallel with the extremal case, there are two available solutions for a given
temperature and angular momentum, one stable and one unstable. In order to
write down the equations of motion, action and conserved charges for the
thermal giant graviton we present a slight generalization of the blackfold
formalism for charged black branes. Finally, we also briefly consider the
thermal giant graviton moving in the AdS_5 part.Comment: v1: 32 pages + 11 pages appendices, 13 figures, v2: typos fixed in
Sec.2 and other misprints, references adde
Non-planar ABJM Theory and Integrability
Using an effective vertex method we explicitly derive the two-loop dilatation
generator of ABJM theory in its SU(2)xSU(2) sector, including all non-planar
corrections. Subsequently, we apply this generator to a series of finite length
operators as well as to two different types of BMN operators. As in N=4 SYM, at
the planar level the finite length operators are found to exhibit a degeneracy
between certain pairs of operators with opposite parity - a degeneracy which
can be attributed to the existence of an extra conserved charge and thus to the
integrability of the planar theory. When non-planar corrections are taken into
account the degeneracies between parity pairs disappear hinting the absence of
higher conserved charges. The analysis of the BMN operators resembles that of
N=4 SYM. Additional non-planar terms appear for BMN operators of finite length
but once the strict BMN limit is taken these terms disappear.Comment: 1+26 pages, uses axodraw.sty. v2: typos fixed, references added. v3:
more typos fixed, minor correction
Holographic 3-point function at one loop
We explore the recent weak/strong coupling match of three-point functions in
the AdS/CFT correspondence for two semi-classical operators and one light
chiral primary operator found by Escobedo et al. This match is between the
tree-level three-point function with the two semi-classical operators described
by coherent states while on the string side the three-point function is found
in the Frolov-Tseytlin limit. We compute the one-loop correction to the
three-point function on the gauge theory side and compare this to the
corresponding correction on the string theory side. We find that the
corrections do not match. Finally, we discuss the possibility of further
contributions on the gauge theory side that can alter our results.Comment: 24 pages, 2 figures. v2: Typos fixed, Ref. added, figure improved.
v3: Several typos and misprints fixed, Ref. updated, figures improved, new
section 2.3 added on correction from spin-flipped coherent state,
computations on string theory side improve
New Penrose Limits and AdS/CFT
We find a new Penrose limit of AdS_5 x S^5 giving the maximally
supersymmetric pp-wave background with two explicit space-like isometries. This
is an important missing piece in studying the AdS/CFT correspondence in certain
subsectors. In particular whereas the Penrose limit giving one space-like
isometry is useful for the SU(2) sector of N=4 SYM, this new Penrose limit is
instead useful for studying the SU(2|3) and SU(1,2|3) sectors. In addition to
the new Penrose limit of AdS_5 x S^5 we also find a new Penrose limit of AdS_4
x CP^3.Comment: 30 page
The superstring Hagedorn temperature in a pp-wave background
The thermodynamics of type IIB superstring theory in the maximally
supersymmetric plane wave background is studied. We compute the thermodynamic
partition function for non-interacting strings exactly and the result differs
slightly from previous computations. We clarify some of the issues related to
the Hagedorn temperature in the limits of small and large constant RR 5-form.
We study the thermodynamic behavior of strings in the case of geometries in the presence of NS-NS and RR 3-form backgrounds. We
also comment on the relationship of string thermodynamics and the thermodynamic
behavior of the sector of Yang-Mills theory which is the holographic dual of
the string theory.Comment: 22 pages, JHEP style, minor misprints corrected, some comments adde
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