149 research outputs found
The Hagedorn temperature in a decoupled sector of AdS/CFT
We match the Hagedorn/deconfinement temperature of planar N=4 super
Yang-Mills (SYM) on R x S^3 to the Hagedorn temperature of string theory on
AdS_5 x S^5. The match is done in a near-critical region where both gauge
theory and string theory are weakly coupled. On the gauge theory side we are
taking a decoupling limit found in hep-th/0605234 in which the physics of
planar N=4 SYM is given exactly by the ferromagnetic XXX_{1/2} Heisenberg spin
chain. We find moreover a general relation between the Hagedorn/deconfinement
temperature and the thermodynamics of the Heisenberg spin chain. On the string
theory side, we identify the dual limit which is taken of string theory on a
maximally symmetric pp-wave background with a flat direction, obtained from a
Penrose limit of AdS_5 x S^5. We compute the Hagedorn temperature of the string
theory and find agreement with the Hagedorn/deconfinement temperature computed
on the gauge theory side. Finally, we discuss a modified decoupling limit in
which planar N=4 SYM reduces to the XXX_{1/2} Heisenberg spin chain with an
external magnetic field.Comment: 7 pages. Talk presented by MO at the RTN workshop, Napoli, Oct. 9-13,
200
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
Dynamics of Structural Elements of GB1 β-Hairpin Revealed by Tryptophan-Cysteine Contact Formation Experiments
Quenching of the triplet state of tryptophan by close contact with cysteine provides a tool for measuring the rate of intramolecular contact formation, one of the most elementary events in the folding process, in peptides and proteins using only natural probes. Here we present a study performed on a stabilized mutant of the second \u3b2-hairpin of the GB1 domain, where we combine steady-state fluorescence, laser-induced temperature-jump, and contact formation measurements to unveil the role of elementary structural components on hairpin dynamics and overall stability. In particular, our methodology provides access to the conformational dynamics of both the folded and unfolded state of the hairpin under native conditions, revealing the presence of extremely slow dynamics on the microsecond time scale in the unfolded state and coexistence of structures with partial pairing of the tails in the folded state. Comparing model peptides that mimic the turn sequence, we found that both ion pairing and hydrogen bonding due to the threonine side chain contribute to the propensity of turn formation but not to the much slower dynamics of the hydrophobic core formation. Interestingly, the dynamics of the turn region in isolation are significantly faster than the dynamics measured for the unfolded state of the complete hairpin, suggesting that non-native hydrophobic contacts slow down the reconfiguration dynamics of the unfolded state. Overall, the information extracted from these experiments provides kinetic limits on interconversions among conformational populations, hence enabling a simplified multistate free-energy landscape for the GB1 hairpin to be drawn
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
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
Divergence Cancellation and Loop Corrections in String Field Theory on a Plane Wave Background
We investigate the one-loop energy shift E to certain two-impurity string
states in light-cone string field theory on a plane wave background. We find
that there exist logarithmic divergences in the sums over intermediate mode
numbers which cancel between the cubic Hamiltonian and quartic ``contact
term''. Analyzing the impurity non-conserving channel we find that the
non-perturbative, order g_2^2 sqrt(lambda') contribution to E/mu predicted in
hep-th/0211220 is in fact an artifact of these logarithmic divergences and
vanishes with them, leaving an order g_2^2 lambda' contribution. Exploiting the
supersymmetry algebra, we present a form for the energy shift which appears to
be manifestly convergent and free of non-perturbative terms. We use this form
to argue that E/mu receives order g_2^2 lambda' contributions at every order in
intermediate state impurities.Comment: 27 pages; added references, acknowledgments, missing normalization in
equations 2.3 - 2.8, also cleaned up notation, and added a few footnote
Matching gauge theory and string theory in a decoupling limit of AdS/CFT
We identify a regime of the AdS/CFT correspondence in which we can
quantitatively match N=4 super Yang-Mills (SYM) for small 't Hooft coupling
with weakly coupled type IIB string theory on AdS_5 x S^5. We approach this
regime by taking the same decoupling limit on both sides of the correspondence.
On the gauge theory side only the states in the SU(2) sector survive, and in
the planar limit the Hamiltonian is given by the XXX_{1/2} Heisenberg spin
chain. On the string theory side we show that the decoupling limit corresponds
to a non-relativistic limit. In this limit some of the bosonic modes and all of
the fermionic modes of the string become infinitely heavy and decouple. We
first take the decoupling limit of the string sigma-model classically. This
enables us to identify a semi-classical regime with semi-classical string
states even though we are in a regime corresponding to small 't Hooft coupling.
We furthermore analyze the quantum corrections that enter in taking the limit.
From this we infer that gauge theory and string theory match, both in terms
of the action and the spectrum, for the leading part and the first correction
away from the semi-classical regime. Finally we consider the implications for
the hitherto unexplained matching of the one-loop contribution to the energy of
certain gauge theory and string theory states, and we explain how our results
give a firm basis for the matching of the Hagedorn temperature in
hep-th/0608115.Comment: 29 pages, 1 figure. v2: Version published in JHEP, section 4 improve
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