65 research outputs found
Gluon scattering in Super Yang-Mills at finite temperature
We extend the AdS/CFT prescription of Alday and Maldacena to finite
temperature , defining the amplitude for gluon scattering in
Super Yang-Mills at strong coupling from string theory. It is defined by a
lightlike ''Wilson loop'' living at the horizon of the T-dual to the black hole
in AdS space. Unlike the zero temperature case, this is different from the
Wilson loop contour defined at the boundary of the AdS black hole metric, thus
at finite there is no relation between gluon scattering amplitudes and the
Wilson loop. We calculate the amplitude at strong coupling for forward
scattering of a low energy gluon () off a high energy gluon () in
both cut-off and generalized dimensional regularization. The generalized
dimensional regularization is defined in string theory as an IR modified
dimensional reduction. For this calculation, the corresponding usual Wilson
loop is related to the jet quenching parameter of the finite temperature SYM plasma, while the gluon scattering amplitude is related to the
viscosity coefficient.Comment: 33 pages, 9 figures; clarifications of some points added, reference
adde
't Hooft Operators in Gauge Theory from Toda CFT
We construct loop operators in two dimensional Toda CFT and calculate with
them the exact expectation value of certain supersymmetric 't Hooft and dyonic
loop operators in four dimensional \Ncal=2 gauge theories with SU(N) gauge
group. Explicit formulae for 't Hooft and dyonic operators in \Ncal=2^* and
\Ncal=2 conformal SQCD with SU(N) gauge group are presented. We also briefly
speculate on the Toda CFT realization of arbitrary loop operators in these
gauge theories in terms of topological web operators in Toda CFT.Comment: 49 pages, LaTeX. Typos fixed, references adde
Exact Results in D=2 Supersymmetric Gauge Theories
We compute exactly the partition function of two dimensional N=(2,2) gauge
theories on S^2 and show that it admits two dual descriptions: either as an
integral over the Coulomb branch or as a sum over vortex and anti-vortex
excitations on the Higgs branches of the theory. We further demonstrate that
correlation functions in two dimensional Liouville/Toda CFT compute the S^2
partition function for a class of N=(2,2) gauge theories, thereby uncovering
novel modular properties in two dimensional gauge theories. Some of these gauge
theories flow in the infrared to Calabi-Yau sigma models - such as the conifold
- and the topology changing flop transition is realized as crossing symmetry in
Liouville/Toda CFT. Evidence for Seiberg duality in two dimensions is exhibited
by demonstrating that the partition function of conjectured Seiberg dual pairs
are the same.Comment: 78 pages, LaTeX; v2: small corrections and references added; v3: JHEP
version, discussing factorization further in new appendix F; v4: sign
corrected for non simply-connected gauge grou
On 3d extensions of AGT relation
An extension of the AGT relation from two to three dimensions begins from
connecting the theory on domain wall between some two S-dual SYM models with
the 3d Chern-Simons theory. The simplest kind of such a relation would
presumably connect traces of the modular kernels in 2d conformal theory with
knot invariants. Indeed, the both quantities are very similar, especially if
represented as integrals of the products of quantum dilogarithm functions.
However, there are also various differences, especially in the "conservation
laws" for integration variables, which hold for the monodromy traces, but not
for the knot invariants. We also discuss another possibility: interpretation of
knot invariants as solutions to the Baxter equations for the relativistic Toda
system. This implies another AGT like relation: between 3d Chern-Simons theory
and the Nekrasov-Shatashvili limit of the 5d SYM.Comment: 23 page
Nonperturbative scales in AdS/CFT
The cusp anomalous dimension is a ubiquitous quantity in four-dimensional
gauge theories, ranging from QCD to maximally supersymmetric N=4 Yang-Mills
theory, and it is one of the best investigated observables in the AdS/CFT
correspondence. In planar N=4 SYM theory, its perturbative expansion at weak
coupling has a finite radius of convergence while at strong coupling it admits
an expansion in inverse powers of the 't Hooft coupling which is given by a
non-Borel summable asymptotic series. We study the cusp anomalous dimension in
the transition regime from strong to weak coupling and argue that the
transition is driven by nonperturbative, exponentially suppressed corrections.
To compute these corrections, we revisit the calculation of the cusp anomalous
dimension in planar N=4 SYM theory and extend the previous analysis by taking
into account nonperturbative effects. We demonstrate that the scale
parameterizing nonperturbative corrections coincides with the mass gap of the
two-dimensional bosonic O(6) sigma model embedded into the AdS_5xS^5 string
theory. This result is in agreement with the prediction coming from the string
theory consideration.Comment: 49 pages, 1 figure; v2: minor corrections, references adde
QCD and strongly coupled gauge theories : challenges and perspectives
We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.Peer reviewe
Lawson criterion for ignition exceeded in an inertial fusion experiment
For more than half a century, researchers around the world have been engaged in attempts to achieve fusion ignition as a proof of principle of various fusion concepts. Following the Lawson criterion, an ignited plasma is one where the fusion heating power is high enough to overcome all the physical processes that cool the fusion plasma, creating a positive thermodynamic feedback loop with rapidly increasing temperature. In inertially confined fusion, ignition is a state where the fusion plasma can begin "burn propagation" into surrounding cold fuel, enabling the possibility of high energy gain. While "scientific breakeven" (i.e., unity target gain) has not yet been achieved (here target gain is 0.72, 1.37Â MJ of fusion for 1.92Â MJ of laser energy), this Letter reports the first controlled fusion experiment, using laser indirect drive, on the National Ignition Facility to produce capsule gain (here 5.8) and reach ignition by nine different formulations of the Lawson criterion
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