D-brane Probes Research Articles

Overlaps and fermionic dualities for integrable super spin chains

The mathfrak{psu}left(2,left.2right|4right) integrable super spin chain underlying the AdS/CFT correspondence has integrable boundary states which describe set-ups where k D3-branes get dissolved in a probe D5-brane. Overlaps between Bethe eigenstates and these boundary states encode the one-point functions of conformal operators and are expressed in terms of the superdeterminant of the Gaudin matrix that in turn depends on the Dynkin diagram of the symmetry algebra. The different possible Dynkin diagrams of super Lie algebras are related via fermionic dualities and we determine how overlap formulae transform under these dualities. As an application we show how to consistently move between overlap formulae obtained for k = 1 from different Dynkin diagrams.

D5-brane on topological black holes

Abstract Our interest is in finding the difference in behavior between black holes with three different topologies. These black holes have spherical, hyperbolic and toroidal structures. We study in this paper the behavior of probe D5-branes in this nontrivial black hole spacetime. We would like to find the solution that describes the embedding of a probe D5-brane. This system realizes an “interface” solution, a kind of non-local operators, on the boundary gauge theories. These operators are important to deepen understanding of AdS/CFT correspondence.

On BPS strings in mathcal{N} = 4 Yang-Mills theory

We study singular time-dependent frac{1}{8} -BPS configurations in the abelian sector of mathcal{N} = 4 supersymmetric Yang-Mills theory that represent BPS string-like defects in ℝ × S3 spacetime. Such BPS strings can be described as intersections of the zeros of holomorphic functions in two complex variables with a 3-sphere. We argue that these BPS strings map to frac{1}{8} -BPS surface operators under the state-operator correspondence of the CFT. We show that the string defects are holographically dual to noncompact probe D3-branes in global AdS5 × S5 that share supersymmetries with a class of dual-giant gravitons. For simple configurations, we demonstrate how to define a good variational problem and propose a regularization scheme that leads to finite energy and global charges on both sides of the holographic correspondence.

Stringy structure at the BPS bound

We explore the stringy structure of 1/2-BPS bound states of NS fivebranes carrying momentum or fundamental string charge, in the decoupling limits leading to little string theory and to AdS3/CFT2 duality. We develop an exact worldsheet description of these states using null-gauged sigma models, and illustrate the construction by deriving the closed-form solution sourced by an elliptical NS5-F1 supertube. The Calabi-Yau/Landau-Ginsburg correspondence maps this geometrical worldsheet description to a non-compact LG model whose superpotential is determined by the fivebrane source configuration. Singular limits of the 1/2-BPS configuration space result when the fivebrane worldvolume self-intersects, as can be seen from both sides of the CY/LG duality — on the Landau-Ginsburg side from the degeneration of the superpotential(s), and on the geometrical side from an analysis of D-brane probes. These singular limits are a portal to black hole formation via the condensation of the branes that are becoming massless, and thus exhibit in the gravitational bulk description the central actors in the non-gravitational dual theory underlying black hole thermodynamics.

Holographic Schwinger effect in a soft wall AdS/QCD model * *Supported by the NSFC (11705166) and the Fundamental Research Funds for the Central Universities, China University of Geosciences (Wuhan) (CUGL180402)

We perform a potential analysis for the holographic Schwinger effect in a deformed model with conformal invariance broken by a background dilaton. We evaluated the static potential by analyzing the classical action of a string attached to a rectangular Wilson loop on a probe D3 brane located at an intermediate position in the bulk AdS space. We observed that the inclusion of the chemical potential tends to enhance the production rate, which is opposite to the effect of the confining scale. In addition, we calculated the critical electric field based on the Dirac-Born-Infeld (DBI) action.

Giant Wilson loops and AdS2/dCFT1

The 1/2-BPS Wilson loop in mathcal{N} = 4 supersymmetric Yang-Mills theory is an important and well-studied example of conformal defect. In particular, much work has been done for the correlation functions of operator insertions on the Wilson loop in the fundamental representation. In this paper, we extend such analyses to Wilson loops in the large-rank symmetric and antisymmetric representations, which correspond to probe D3 and D5 branes with AdS2× S2 and AdS2× S4 worldvolume geometries, ending at the AdS5 boundary along a one-dimensional contour. We first compute the correlation functions of protected scalar insertions from supersymmetric localization, and obtain a representation in terms of multiple integrals that are similar to the eigenvalue integrals of the random matrix, but with important differences. Using ideas from the Fermi Gas formalism and the Clustering method, we evaluate their large N limit exactly as a function of the ’t Hooft coupling. The results are given by simple integrals of polynomials that resemble the Q-functions of the Quantum Spectral Curve, with integration measures depending on the number of insertions. Next, we study the correlation functions of fluctuations on the probe D3 and D5 branes in AdS. We compute a selection of three- and four-point functions from perturbation theory on the D-branes, and show that they agree with the results of localization when restricted to supersymmetric kinematics. We also explain how the difference of the internal geometries of the D3 and D5 branes manifests itself in the localization computation.

D3-brane loop amplitudes from M5-brane tree amplitudes

We study loop corrections to scattering amplitudes in the world-volume theory of a probe D3-brane, which is described by the supersymmetric Dirac-Born-Infeld theory. We show that the D3-brane loop superamplitudes can be obtained from the tree-level superamplitudes in the world-volume theory of a probe M5-brane (or D5-brane). The M5-brane theory describes self-interactions of an abelian tensor supermultiplet with (2, 0) supersymmetry, and the tree-level superamplitudes are given by a twistor formula. We apply the construction to the maximally-helicity-violating (MHV) amplitudes in the D3- brane theory at one-loop order, which are purely rational terms (except for the four-point amplitude). The results are further confirmed by generalised unitarity methods. Through a supersymmetry reduction on the M5-brane tree-level superamplitudes, we also construct one-loop corrections to the non-supersymmetric D3-brane amplitudes, which agree with the known results in the literature.

Melting holographic mesons by cooling a magnetized quark gluon plasma

We extend our analysis of holographic meson dissociation in the presence of an intense magnetic field. In addition to the previously known critical temperature above which the mesons melt, we found that for certain magnetic field intensities there exists a second lower critical temperature, below which stable mesons cease to exist. While we showed before that there is a range of high temperatures for which mesons can be melted by changing the magnetic field intensity, here we show that, as a consequence of the second critical point, there is also a range of low temperatures for which this phenomenom, which we term Magnetic Meson Melting (MMM), can be triggered. Additionaly, we also show that the magnetic field decreases the mass gap of the meson spectrum along with their masses. We are able to observe this by constructing a configuration that makes it possible to apply gauge/gravity methods to study fundamental degrees of freedom in a quark-gluon plasma subject to a magnetic field as intense as that expected in high energy collisions. This is achieved by the confection of a ten-dimensional background that is dual to the magnetized plasma and nonetheless permits the embedding of D7-branes in it. The main difference with previous approaches, which in consequence gives the novel results, is that the magnetic field retroacts in the geometry itself, as opposed to be confined to the world volume of the probe D7-branes.

Holographic Wilson lines as screened impurities

In Landau Fermi liquids, screened impurities support quasi-bound states, representing electrons bound to the impurity but making virtual excursions away. Signals of these quasi-bound states are electron-impurity scattering phase shifts and the corresponding resonances in cross sections. We consider large-N , strongly-coupled (3 + 1)-dimensional mathcal{N} = 4 supersymmetric SU(N ) Yang-Mills theory on the Coulomb branch, where an adjoint scalar has a non-zero expectation value that breaks SU(N ) → SU(N − 1) × U(1). In the holographic dual we re-visit well-known solutions for a probe D3-brane that describe this theory with a symmetric-representation Wilson line “impurity”. We present evidence that the adjoint scalar screens the Wilson line, by showing that quasi-bound states form at the impurity, producing U(1)-impurity scattering phase shifts and corresponding resonances in cross sections. The quasi-bound states appear holographically as quasi-normal modes of probe D3-brane fields, even in the absence of a black hole horizon, via a mechanism that we argue is generic to screened defects in holography. We also argue that well-known generalisations of these probe D3-brane solutions can describe lattices of screened Wilson/’t Hooft line impurities.

Circular Wilson loops in defect mathcal{N} = 4 SYM: phase transitions, double-scaling limits and OPE expansions

We consider circular Wilson loops in a defect version of mathcal{N} = 4 super-Yang- Mills theory which is dual to the D3-D5 brane system with k units of flux. When the loops are parallel to the defect, we can construct both BPS and non-BPS operators, depending on the orientation of the scalar couplings in the R-symmetry directions. At strong ’t Hooft coupling we observe, in the non supersymmetric case, a Gross-Ooguri-like phase transition in the dual gravitational theory: the familiar disk solution dominates, as expected, when the operator is far from the defect while a cylindrical string worldsheet, connecting the boundary loop with the probe D5-brane, is favourite below a certain distance (or equivalently for large radii of the circles). In the BPS case, instead, the cylindrical solution does not exist for any choice of the physical parameters, suggesting that the exchange of light supergravity modes always saturate the expectation value at strong coupling. We study the double-scaling limit for large k and large ’t Hooft coupling, finding full consistency in the non-BPS case between the string solution and the one-loop perturbative result. Finally we discuss, in the BPS case, the failure of the double-scaling limit and the OPE expansion of the Wilson loop, finding consistency with the known results for the one-point functions of scalar composite operators.

Interface in AdS black hole spacetime

Abstract We consider a defect solution in the anti-de Sitter (AdS) black hole spacetime. This is a generalization of the previous work [K. Nagasaki et al., J. High Energy Phys. 1201, 139 (2012)] to another spacetime. This system consists of D3- and D5-branes. The equation of motion for a sort of nonlocal operator, an “interface”, is given and its numerical solution is shown by the numerical calculation. We also consider a string extending between this interface and the boundary of the AdS spacetime. This corresponds to the quark–interface potential in the boundary theory of the bulk black hole spacetime. This result gives a new example of a holographic relation that includes the gauge flux in the probe D5-brane.

Effect of the gluon condensate on the holographic Schwinger effect

We perform the potential analysis in holographic Schwinger effect in a deformed anti-de Sitter (AdS) background with backreaction due to the gluon condensate. We determine the potential by analyzing the classical string action attaching on a probe D3-brane sitting at an intermediate position in the bulk AdS space. It is found that the inclusion of the gluon condensate reduces the production rate, reverse to the effect of the temperature. Also, we evaluate the critical electric field by Dirac-Born-Infeld (DBI) action.

Fat inflatons, large turns and the η-problem

It is commonly believed that a successful period of inflation driven by a single or several scalar fields requires a specific hierarchy of masses given by Minf≪ H ≪ Mheavy, where Minf can correspond to several or a single light field and Mheavy corresponds to any heavy field that might be integrated out if it satisfies suitable conditions. This is at the heart of the so called η-problem in inflation, since large contributions to the masses of the inflatons might spoil the slow-roll conditions required for inflation. We show that, while this is an unavoidable conclusion in single field inflation, in multifield inflation, heavy fields as defined above, may be fully responsible for a successful period of what we call fat slow-roll inflation. Moreover we show that in this scenario, the turning rate of the inflationary trajectory, Ω/H, is larger than one. Thus, the η-problem is evaded with large turns in fat inflation. Depending on the perturbations' mass spectra, cosmological predictions will differ either slightly or largely with respect to those of the single field case. We illustrate this scenario in a concrete example in Type IIB string flux compactifications, where a probe D5-brane moving along the angular and radial directions in a warped throat drives fat D5-brane natural inflation. An instantaneous superplanckian decay constant can be defined, consistent with our low energy approximations. We compute the cosmological observables, which are consistent with Planck data, ameliorating the tension of single field natural inflation with observations. We also discuss fat inflation in the context of recently proposed swampland de Sitter conjectures.

Critical point in a holographic defect field theory

We study a holographic gauge theory dual to the D3/D5 intersection. We consider a pure gauge B-field flux through the internal two-sphere wrapped by the probe D5-brane, which corresponds to a non-commutative configuration of adjoint scalars. There is a domain wall separating the theory into regions with different ranks of the adjoint group. At zero temperature the theory is supersymmetric and at finite temperature there is a critical point of a second order phase transition. We study the corresponding critical exponents and find that the second derivatives of the free energy, with respect to the bare mass and the magnetic field, diverge with a critical exponent of −2/3.

Spectrum of a supersymmetric color superconductor

We have recently shown that the ground state of mathcal{N} = 4, SU(Nc) super Yang- Mills coupled to Nf ≪ Nc flavors, in the presence of non-zero isospin and R-symmetry charges, is a supersymmetric, superfluid, color superconductor. The holographic description consists of Nf D7-brane probes in AdS5×S5 with electric and instantonic fields on their worldvolume. These correspond to fundamental strings and D3-branes dissolved on the D7-branes, respectively. Here we use this description to determine the spectrum of mesonic excitations. As expected for a charged superfluid we find non-relativistic, massless Goldstone modes. We also find extra ungapped modes that are not associated to the breaking of any global symmetries but to the supersymmetric nature of the ground state. If the quark mass is much smaller than the scale of spontaneous symmetry breaking a pseudo-Goldstone boson is also present. We highlight some new features that appear only for Nf> 2. We show that, in the generic case of unequal R-symmetry charges, the dissolved strings and D3-branes blow up into a D5-brane supertube stretched between the D7-branes.

Little strings, long strings, and fuzzballs

At high energy densities, fivebranes are populated by a Hagedorn phase of so- called little strings, whose statistical mechanics underlies black fivebrane thermodynamics. A particular limit of this phase yields BTZ black holes in AdS3, leading us to the idea that in this context fuzzballs and highly excited little strings are one and the same. We explore these ideas through an analysis of D-brane probes of fivebrane supertube backgrounds. String theory dynamics on these backgrounds is described by an exactly solvable null- gauged WZW model. We develop the formalism of null gauging on worldsheets with boundaries, and find that D-branes wrapping topology at the bottom of the supertube throat are avatars of the “long string” structure that dominates the thermodynamics of the black hole regime, appearing here as excitations of supertubes lying near but slightly outside the black hole regime.

A non-integrable quench from AdS/dCFT

We study the matrix product state which appears as the boundary state of the AdS/dCFT set-up where a probe D7 brane wraps two two-spheres stabilized by fluxes. The matrix product state plays a dual role, on one hand acting as a tool for computing one-point functions in a domain wall version of N=4 SYM and on the other hand acting as the initial state in the study of quantum quenches of the Heisenberg spin chain. We derive a number of selection rules for the overlaps between the matrix product state and the eigenstates of the Heisenberg spin chain and in particular demonstrate that the matrix product state does not fulfil a recently proposed integrability criterion. Accordingly, we find that the overlaps can not be expressed in the usual factorized determinant form. Nevertheless, we derive some exact results for one-point functions of simple operators and present a closed formula for one-point functions of more general operators in the limit of large spin-chain length.

A supersymmetric color superconductor from holography

We use holography to study d = 4, mathcal{N}=4 , SU(Nc) super Yang-Mills coupled to Nf ≪ Nc quark flavors. We place the theory at finite isospin density nI by turning on an isospin chemical potential μI = Mq, with Mq the quark mass. We also turn on two R-symmetry charge densities n1 = n2. We show that the ground state is a supersymmetric, superfluid, color superconductor, namely a finite-density state that preserves a fraction of supersymmetry in which part of the global symmetries and part of the gauge symmetries are spontaneously broken. The holographic description consists of Nf D7-brane probes in AdS5 × S5. The symmetry breaking is due to the dissolution of some D3-branes inside the D7-branes triggered by the electric field associated to the isospin charge. The massless spectrum contains Goldstone bosons and their fermionic superpartners. The massive spectrum contains long-lived, mesonic quasi-particles if nI ≪ μI3, and no quasi-particles otherwise. We discuss the possibility that, despite the presence of mass scales and charge densities in the theory, conformal and relativistic invariance arise as emergent symmetries in the infrared.

Confining D-instanton background in an external electric field

Using holography, we discuss the effects of an external static electric field on the D3/D-instanton theory at zero-temperature, which is a quasi-confining theory, with confined quarks and deconfined gluons. We introduce the quarks to the theory by embedding a probe D7-brane in the gravity side, and turn on an appropriate U(1) gauge field on the flavor brane to describe the electric field. Studying the embedding of the D7-brane for different values of the electric field, instanton density and quark masses, we thoroughly explore the possible phases of the system. We find two critical points in our considerations. We show that beside the usual critical electric field present in deconfined theories, there exists another critical field, with smaller value, below which no quark pairs even the ones with zero mass are produced and thus the electric current is zero in this (insulator) phase. At the same point, the chiral symmetry, spontaneously broken due to the gluon condensate, is restored which shows a first order phase transition. Finally, we obtain the full decay rate calculating the imaginary part of the DBI action of the probe brane and find that it becomes nonzero only when the critical value of the electric field is reached.

String memory effect

In systems with local gauge symmetries, the memory effect corresponds to traces inscribed on a suitable probe when a pure gauge configuration at infinite past dynamically evolves to another pure gauge configuration at infinite future. In this work, we study the memory effect of 2-form gauge fields which is probed by strings. We discuss the “string memory effect” for closed and open strings at classical and quantum levels. The closed string memory is encoded in the internal excited modes of the string, and in the open string case, it is encoded in the relative position of the two endpoints and the non-commutativity parameter associated with the D-brane where the open string endpoints are attached. We also discuss 2-form memory with D-brane probes using boundary state formulation and, the relation between string memory and 2-form soft charges analyzed in [1].