119279865
Lattice four-dimensional N=4 SYM is practical
We show that nonperturbative lattice studies of four-dimensional N=4 Super-Yang-Mills are within reach. We use Ginsparg-Wilson fermions to avoid gluino masses and an exact implementation of the (chiral) $R$-symmetry, which greatly limits the number of counterterms that must be fine-tuned. Only bosonic operators require fine tuning, so all tunings can be done ``offline'' by a Ferrenberg-Swendsen type reweighting. We show what measurables can be used to perform the tuning.
10799212
Classical field dynamics of the electroweak phase transition
We investigate the thermodynamics and dynamics of the electroweak phase transition by modeling the infrared physics with classical Yang-Mills Higgs theory. We discuss the accuracy of this approach and conclude that, for quantities whose determination is dominated by the infrared, the classical method should be correct up to parametrically suppressed [i.e., O({alpha})] corrections. For a Higgs self-coupling which at the tree level corresponds to m{sub H}{approx_equal}50 GeV, we determine the jump in the order parameter to be {delta}{phi}=1.5gT, the surface tension to be {sigma}=0.07g{sup 4}T{sup 3}, and the friction coefficient on the moving bubble wall due to infrared bosons to be {eta}{equivalent_to}P/v{sub w}=0.03{plus_minus}0.004g{sup 6}T{sup 4}. We also investigate the response of the Chern-Simons number to a spatially uniform chemical potential and find that it falls off a short distance inside the bubble wall, both in equilibrium and below the equilibrium temperature. {copyright} {ital 1997} {ital The American Physical Society}
18843095
Classical sphaleron rate on fine lattices
We measure the sphaleron rate for hot, classical Yang-Mills theory on the lattice, in order to study its dependence on lattice spacing. By using a topological definition of Chern-Simons number and going to extremely fine lattices [up to $\ensuremath{\beta}=32,$ or lattice spacing ${a=1/(8g}^{2}T)]$ we demonstrate nontrivial scaling. The topological susceptibility, converted to physical units, falls with lattice spacing on fine lattices in a way which is consistent with linear dependence on a (the Arnold-Son-Yaffe scaling relation) and is difficult to reconcile with a nonzero continuum limit. We also explain some unusual behavior of the rate in small volumes, reported by Ambj\o{}rn and Krasnitz.
118416779
Next-to-leading order thermal photon production in a weakly coupled quark-gluon plasma
A bstractWe compute the next-to-leading order O(g) correction to the thermal photon production rate in a QCD plasma. The NLO contributions can be expressed in terms of gauge invariant condensates on the light cone, which are amenable to novel sum rules and Euclidean techniques. We expect these technologies to be generalizable to other NLO calculations. For the phenomenologically interesting value of αs = 0.3, the NLO correction represents a 20% increase and has a functional form similar to the LO result.
119023526
The phantom menaced: Constraints on low-energy effective ghosts
It has been suggested that a scalar field with negative kinetic energy, or ``ghost,'' could be the source of the observed late-time cosmological acceleration. Naively, such theories should be ruled out by the catastrophic quantum instability of the vacuum. We derive phenomenological bounds on the Lorentz-violating ultraviolet cutoff $\ensuremath{\Lambda}$ which must apply to low-energy effective theories of ghosts, in order to keep the instability at unobservable levels. Assuming only that ghosts interact at least gravitationally, we show that $\ensuremath{\Lambda}\ensuremath{\lesssim}3\mathrm{MeV}$ for consistency with the cosmic gamma ray background. We also show that theories of ghosts with a Lorentz-conserving cutoff are completely excluded.
119279378
Bjorken flow, plasma instabilities, and thermalization
A bstractAt asymptotically high energies, thermalization in heavy ion collisions can be described via weak-coupling QCD. We present a complete treatment of how thermalization proceeds, at the parametric weak-coupling level. We show that plasma instabilities dominate the dynamics, from immediately after the collision until well after the plasma becomes nearly in equilibrium. Initially they drive the system close to isotropy, but Bjorken expansion and increasing diluteness makes the system again become more anisotropic. At time $ \tau \sim {\alpha^{{\frac{{ - 12}}{5}}}}Q_s^{{ - 1}} $ the dynamics become dominated by a nearly-thermal bath; and at time $ \tau \sim {\alpha^{{\frac{{ - 5}}{2}}}}Q_s^{{ - 1}} $ the bath comes to dominate the energy density, completing thermalization. After this time there is a nearly isotropic and thermal Quark-Gluon Plasma.
15664546
Some exact results on tachyon condensation in string field theory
The study of open string tachyon condensation in string field theory can be drastically simplified by making an appropriate choice of coordinates on the space of string fields. We show that a very natural coordinate system is suggested by the connection between the worldsheet renormalization group and spacetime physics. In this system only one field, the tachyon, condenses while all other fields have vanishing expectation values. These coordinates are also well-suited to the study of D-branes as solitons. We use them to show that the tension of the D25-brane is cancelled by tachyon condensation and compute exactly the profiles and tensions of lower dimensional D-branes.
115179854
Orientifold Precis
We give a precise and concise formulation of the orientifold construction in Type II superstring theory. Our results include anomaly cancellation on the worldsheet and a K-theoretic computation of the background Ramond-Ramond charge. Since its inception [Sa, PS, Ho, DLP, BiS] the orientifold construction of Type II superstring theory has proven useful both for the formal development of string theory and for its potential applications to phenomenology. For reviews see [P, D, AnS, BH1, J, BH2, BHHW]. Our work began many years ago when the first author showed the second the formula [DJM, CR, MSS, S, SS] for the Ramond-Ramond charge induced by an orientifold and inquired about its K-theoretic significance, especially in view of the unusual cousin of the Hirzebruch L-genus contained therein. In the process of our investigations we were led to more foundational questions about orientifolds and the Type II superstring. In this letter we describe some mathematical foundations we have developed to resolve these questions. In particular, we give careful definitions of both the worldsheet and spacetime fields of an orientifold, including precise Dirac quantization conditions for the B-field and Ramond-Ramond (RR) field. The pNeveu-Schwarzq2 NSNS fields which appear in Definition 2 involve subtle topological structures which, for very different reasons, exactly fit what is needed in both the (short distance) worldsheet and (long distance) spacetime theories. The worldsheet fields are enumerated in Definition 4. A surprising challenge here is to define the integral of the B-field over the worldsheet. The lack of a proper orientation leads to a novel prescription, one feature of which is that the B-field amplitude has a (classical) anomaly in the sense that it takes values in a complex line not canonically isomorphic to the complex numbers. It then cancels against the more standard (quantum) anomaly from the spinor field on the worldsheet, and the cancellation uses the “twisted” spin structure in spacetime. The spacetime RR field is self-dual, so part of its formulation (Definition 6) involves a certain quadratic function. The general theory of self-dual fields defines an RR charge due to the orientifold background, which we compute with the prime 2 inverted, in which case it localizes to the orientifold fixed point set. Tensoring with the reals we recover the formula (8) which began this project. Our definitions are new, even in the case of the Type I superstring, and offer some refinements of the standard (non-orientifold) Type II superstring. Taken together the orientifold data is an impressively tight structure, and leads to the most intricate matching we know between topological Date: August 19, 2010. The work of J.D. is supported by the National Science Foundation under grant PHY-0455649. The work of D.S.F. is supported by the National Science Foundation under grant DMS-0603964. The work of G.W.M. is supported by the DOE under grant DE-FG02-96ER40949. We also thank the Aspen Center for Physics for providing a stimulating environment for many discussions related to this paper. Report numbers: UTTG-04-09, TCC-019-09. The twisted spin structure appears in Definition 2.
14015970
I-brane inflow and anomalous couplings on D-branes
We show that the anomalous couplings of D-brane gauge and gravitational fields to Ramond - Ramond tensor potentials can be deduced by a simple anomaly inflow argument applied to intersecting D-branes and use this to determine the 8-form gravitational coupling.
121021214
Some global issues in string perturbation theory
Abstract Calculations of the type II string vacuum amplitude using the picture changing prescription have been shown to lead, in general, to a positive cosmological constant. We show that there is a global obstruction to the choices of gauge slice for super-Teichmuller space that lead to such measures. We discuss the general restrictions on gauge slices appropriate for use in explicit fermionic string calculations. We also discuss the relation of the functional determinant and conformal field theory versions of the path integral measure, and show that, at arbitrary genus and in arbitrary backgrounds preserving tree level N = 1 supersymmetry, the measure is an exact differential. We evaluate the boundary integrals of this total derivative at genus two in two ways for target space R 10 to show that the integrals are zero. Finally, we use the factorization hypothesis to show that in appropriate compactified spacetimes the boundary integrals continue to vanish.
11977234
Ample D4-D2-D0 Decay
We study the wall-crossing behavior of the index of BPS states for D4-D2-D0 brane systems on a Calabi-Yau 3-fold at large radius and point out that not only is the ``BPS index at large radius'' chamber-dependent, but that the changes in the index can be large in the sense that they dominate single-centered black hole entropy. We discuss implications for the weak coupling OSV conjecture. We also analyze the near horizon limit of multicentered solutions, introduced in arXiv:0802.2257, for these particular configurations and comment on a general criterion, conjectured in arXiv:0802.2257, which identifies those multicentered solutions whose near horizon limit corresponds to a geometry with a single asymptotic AdS_3 x S^2 boundary.