Papers by Esperanza Lopez
Journal of High Energy Physics, 2015
ABSTRACT We study holographic models related to global quantum quenches in finite size systems. T... more ABSTRACT We study holographic models related to global quantum quenches in finite size systems. The holographic set up describes naturally a CFT, which we consider on a circle and a sphere. The enhanced symmetry of the conformal group on the circle motivates us to compare the evolution in both cases. Depending on the initial conditions, the dual geometry exhibits oscillations that we holographically interpret as revivals of the initial field theory state. On the sphere, this only happens when the energy density created by the quench is small compared to the system size. However on the circle considerably larger energy densities are compatible with revivals. Two different timescales emerge in this latter case. A collapse time, when the system appears to have dephased, and the revival time, when after rephasing the initial state is partially recovered. The ratio of these two times depends upon the initial conditions in a similar way to what is observed in some experimental setups exhibiting collapse and revivals.
Journal of High Energy Physics, 2002
We study one-loop corrections in scalar and gauge field theories on the non-commutative torus. Fo... more We study one-loop corrections in scalar and gauge field theories on the non-commutative torus. For rational θ, Morita equivalence allows these theories to be reformulated in terms of ordinary theories on a commutative torus with twisted boundary conditions. UV/IR mixing does not lead to singularities, however there can be large corrections. In particular, gauge theories show tachyonic instabilities for some of the modes. We discuss their relevance to spontaneous N × N symmetry breaking in the Morita dual SU (N ) theory due to electric flux condensation.
Journal of High Energy Physics, 1998
We study brane configurations in the presence of orientifold six-planes. After deriving the curve... more We study brane configurations in the presence of orientifold six-planes. After deriving the curves for N = 2 supersymmetric SU (N c ) gauge theories with one flavor in the symmetric or antisymmetric representation and N f fundamental flavors, we rotate the brane configuration, reducing the supersymmetry to N = 1. For the case of an antisymmetric flavor and less than two fundamental flavors, nonperturbative effects lead to a brane configuration that is topologically a torus. Using the description of the orientifold six-planes as D n singularities we discuss the Higgs branches for N = 2 brane configurations with Sp/SO gauge groups and the related N = 1 theories with tensor representations.
Journal of High Energy Physics, 1998
Using a six-orientifold on top of a NS-fivebrane we construct a chiral N = 1 supersymmetric gauge... more Using a six-orientifold on top of a NS-fivebrane we construct a chiral N = 1 supersymmetric gauge theory in four dimensions with gauge group SU (N c ) and matter in the symmetric, antisymmetric and (anti)fundamental representations. Anomaly cancellation is fulfilled by the requirement of a smooth RR 7-form charge distribution and leads us to the introduction of 8 half D-sixbranes ending on the NS-fivebrane. We obtain the dual model from branes by a linking number argument. We check explicitly the 't Hooft anomaly matching conditions and the map between deformations in the original and the dual model.
The integrable systems associated with Seiberg-Witten geometry are considered both from the Hitch... more The integrable systems associated with Seiberg-Witten geometry are considered both from the Hitchin-Donagi-Witten gauge model and in terms of intermediate Jacobians of Calabi-Yau threefolds. Dual pairs and enhancement of gauge symmetries are discussed on the basis of a map from the Donagi-Witten ``moduli'' into the moduli of complex structures of the Calabi-Yau threefold.
Journal of High Energy Physics, 2014
ABSTRACT We study holographically the out of equilibrium dynamics of a finite size closed quantum... more ABSTRACT We study holographically the out of equilibrium dynamics of a finite size closed quantum system in 2+1 dimensions, modelled by the collapse of a shell of a massless scalar field in AdS4. In global coordinates there exists a variety of evolutions towards final black hole formation which we relate with different patterns of relaxation in the dual field theory. For large scalar initial data rapid thermalization is achieved as a priori expected. Interesting phenomena appear for small enough amplitudes. Such shells do not generate a black hole by direct collapse, but quite generically an apparent horizon emerges after enough bounces off the AdS boundary. We relate this bulk evolution with relaxation processes at strong coupling which delay in reaching an ergodic stage. Besides the dynamics of bulk fields, we monitor the entanglement entropy, finding that it oscillates quasi-periodically before final equilibration. The radial position of the traveling shell is brought into correspondence with the evolution of the entanglement pattern in the dual field theory. The entanglement entropy is not only able to portrait the streaming of entangled excitations, but it is also a useful probe of interaction effects.
Physics Letters B, 1995
For N =2 SUSY theories with non vanishing -function and a one dimensional quantum moduli, we stud... more For N =2 SUSY theories with non vanishing -function and a one dimensional quantum moduli, we study the representation on the special coordinates, of the group of motions on the quantum moduli dened by W = Sl(2; Z)= M , with M the quantum monodromy group. W contains both the global symmetries and the strong-weak coupling duality. The action of W on the special coordinates is not part of the symplectic group Sl(2; Z). After coupling to gravity, namely in the context of non-rigid special geometry, w e can dene the action of W as part of Sp(4; Z). To do that requires singular gauge transformations on the "scalar" component of the graviphoton eld. In terms of these singular gauge transformations the topological obstruction to strong-weak duality can be interpreted as a -model anomaly, indicating the possible dynamical role of the dilaton eld in S-duality.
In these notes evidence is presented for intepreting the moduli space of the integrable model ass... more In these notes evidence is presented for intepreting the moduli space of the integrable model associated to $N\!=\!2$ gauge theories with $N\!=\!4$ matter content, in terms of Calabi-Yau manifolds. We restrict to the case of gauge group $SU(2)$, which is compared with the moduli space of the Calabi-Yau manifold $WP_{11226}^{12}$ appearing in the rank three dual pair $(K^{3}\times T^{2} / WP_{11226}^{12})$. The singularity loci of both spaces are maped in a one to one way and, in the weak coupling limit, $N\!=\!2$ $SU(2)$ pure Yang-Mills is obtained in both cases by the same type of blow up. Comments on the interpretation of the strong coupling locus from the perspective of the integrable system are done.
Journal of High Energy Physics, 2011
ABSTRACT We consider a thermalization process in a 2-dimensional CFT that has a holographic descr... more ABSTRACT We consider a thermalization process in a 2-dimensional CFT that has a holographic description in terms of the gravitational collapse of a thin shell of null dust. This model represents a sudden perturbation of the CFT vacuum that communicates a uniform energy density to the system. We study the evolution of two-point functions at spacelike separated points (t1,l) and (t2,0), and reproduce the generic pattern first derived from the analysis of quantum quenches to critical systems. A crucial characteristic of these setups is that the excitations generated by the initial perturbation presents non-trivial quantum correlations. As a consequence, for any ti<infinity equilibration is only effective on finite regions whose size grows as a lightfront. The behavior on larger regions is greatly determined by the initial state, which for the quenches we consider and the holographic model has relevant differences. However in both cases for late times the dependence on the scale l of the two-point functions enters through the effective distance l-t1-t2. We interpret the onset of this behavior as an equilibration time for occupation numbers in these 2-dimensional models.
Journal of High Energy Physics, 2004
The complete one-loop planar dilatation operator of N = 4 supersymmetric Yang-Mills is isomorphic... more The complete one-loop planar dilatation operator of N = 4 supersymmetric Yang-Mills is isomorphic to the hamiltonian of an integrable P SU(2, 2|4) quantum spin chain. We construct the non-linear sigma models describing the continuum limit of the SU(1|3) and SU(2|3) sectors of the complete N = 4 chain. We explicitely identify the spin chain sigma model with the one for a superstring moving in AdS 5 × S 5 with large angular momentum along the five-sphere.
Journal of High Energy Physics, 2005
N = 4 supersymmetric Yang-Mills operators carrying large charges are dual to semiclassical string... more N = 4 supersymmetric Yang-Mills operators carrying large charges are dual to semiclassical strings in AdS 5 × S 5 . The spectrum of anomalous dimensions of very large operators has been calculated solving the Bethe ansatz equations in the thermodynamic limit, and matched to energies of string solitons. We have considered finite size corrections to the Bethe equations, that should correspond to quantum effects on the string side.
Journal of High Energy Physics, 1999
According to the AdS/CFT correspondence, the strong coupling limit of large N N = 4 supersymmetri... more According to the AdS/CFT correspondence, the strong coupling limit of large N N = 4 supersymmetric gauge theory at finite temperature is described by asymptotically anti de Sitter black holes. These black holes exist with planar, spherical and hyperbolic horizon geometries. We concentrate on the hyperbolic and spherical cases and probe the associated gauge theories with D3-branes and Wilson loops. The D3-brane probe reproduces the coupling of the scalars in the gauge theory to the background geometry and we find thermal stabilization in the hyperbolic case. We investigate the vacuum expectation value of Wilson loops with particular emphasis on the screening length at finite temperature. We find that the thermal phase transition of the theory on the sphere is not related to screening phenomena.
Journal of High Energy Physics, 2006
We propose an all-order perturbative expression for the dressing phase of the AdS 5 × S 5 string ... more We propose an all-order perturbative expression for the dressing phase of the AdS 5 × S 5 string S-matrix at strong coupling. Moreover, we are able to sum up large parts of this expression. This allows us to start the investigation of the analytic structure of the phase at finite coupling revealing a few surprising features. The phase obeys all known constraints including the crossing relation and it matches with the known physical data at strong coupling. In particular, we recover the bound states of giant magnons recently found by Hofman and Maldacena as poles of the scattering matrix. At weak coupling our proposal seems to differ with gauge theory. A possible solution to this disagreement is the inclusion of additional pieces in the phase not contributing to crossing, which we also study.
Journal of High Energy Physics, 2000
We study the dispersion relation for scalar excitations in supersymmetric, non-commutative theori... more We study the dispersion relation for scalar excitations in supersymmetric, non-commutative theories at finite temperature. In N = 4 Yang-Mills the low momenta modes have superluminous group velocity. In the massless Wess-Zumino model the minimum of the dispersion relation is at non zero momentum for temperatures above T 0 ≈ (gθ) − 1 2 . We briefly comment on N = 2 Yang-Mills at finite density.
Journal of High Energy Physics, 1999
String or M-theory in the background of Kerr-AdS black holes is thought to be dual to the large N... more String or M-theory in the background of Kerr-AdS black holes is thought to be dual to the large N limit of certain conformal field theories on a rotating sphere at finite temperature. The five dimensional black hole is associated to N = 4 supersymmetric Yang-Mills theory on a rotating three-sphere and the four dimensional one to the superconformal field theory of coinciding M2 branes on a rotating two-sphere. The thermodynamic potentials can be expanded in inverse powers of the radius of the sphere. We compute the leading and subleading terms of this expansion in the field theory at one loop and compare them to the corresponding supergravity expressions. The ratios between these terms at weak and strong coupling turns out not to depend on the rotation parameters in the case of N = 4 SYM. For the field theory living on one M2 brane we find a subleading logarithmic term. No such term arises from the supergravity calculation.
Journal of High Energy Physics, 2004
The ferromagnetic integrable SU(3) spin chain provides the one loop anomalous dimension of single... more The ferromagnetic integrable SU(3) spin chain provides the one loop anomalous dimension of single trace operators involving the three complex scalars of N = 4 supersymmetric Yang-Mills. We construct the non-linear sigma model describing the continuum limit of the SU(3) spin chain. We find that this sigma model corresponds to a string moving with large angular momentum in the five-sphere in AdS 5 × S 5 . The energy and spectrum of fluctuations for rotating circular strings with angular momenta along three orthogonal directions of the five-sphere is reproduced as a particular case from the spin chain sigma model.
Journal of High Energy Physics, 2006
One-loop corrections to the energy of semiclassical rotating strings contain both analytic and no... more One-loop corrections to the energy of semiclassical rotating strings contain both analytic and non-analytic terms in the 't Hooft coupling. Analytic contributions agree with the prediction from the string Bethe ansatz based on the classical S-matrix, but in order to include non-analytic contributions quantum corrections are required. We find a general expression for the first quantum correction to the string Bethe ansatz.
Journal of High Energy Physics, 2002
We discuss nonplanar anomalies in noncommutative gauge theories. In particular we show that a non... more We discuss nonplanar anomalies in noncommutative gauge theories. In particular we show that a nonplanar anomaly exists when the external noncommutative momentum is zero and that it leads to a non-conservation of the associated axial charge. In the case of nonplanar local anomalies, a cancellation of the anomaly can be achieved by a Green-Schwarz mechanism. In an example of D3 branes placed on an orbifold singularity that leads to a chiral theory, the mechanism involves twisted RR fields which propagate with zero noncommutative momentum. Global anomalies are not cancelled and, in particular, the decay π 0 → 2γ is allowed.
Journal of High Energy Physics, 2010
ABSTRACT We study the evolution of entanglement entropy in a 2-dimensional equilibration process ... more ABSTRACT We study the evolution of entanglement entropy in a 2-dimensional equilibration process that has a holographic description in terms of a Vaidya geometry. It models a unitary evolution in which the field theory starts in a pure state, its vacuum, and undergoes a perturbation that brings it far from equilibrium. The entanglement entropy in this set up provides a measurement of the quantum entanglement in the system. Using holographic techniques we recover the same result obtained before from the study of processes triggered by a sudden change in a parameter of the hamiltonian, known as quantum quenches. Namely, entanglement in 2-dimensional conformal field theories propagates with velocity v^2=1. Both in quantum quenches and in the Vaidya model equilibration is only achieved at the local level. Remarkably, the holographic derivation of this last fact requires information from behind the apparent horizon generated in the process of gravitational collapse described by the Vaidya geometry. In the early stages of the evolution the apparent horizon seems however to play no relevant role with regard to the entanglement entropy. We speculate on the possibility of deriving a thermalization time for occupation numbers from our analysis. Comment: 26 pages, 10 figures
Journal of High Energy Physics, 2001
We extend our previous work on the quasi-particle excitations in N = 4 noncommutative U (1) Yang-... more We extend our previous work on the quasi-particle excitations in N = 4 noncommutative U (1) Yang-Mills theory at finite temperature. We show that above some critical temperature there is a tachyon in the spectrum of excitations. It is a collective transverse photon mode polarized in the non-commutative plane. Thus the theory seems to undergo a phase transition at high temperature. Furthermore we find that the group velocity of quasi-particles generically exceeds the speed of light at low momentum.
Uploads
Papers by Esperanza Lopez