arXiv subjects

Ingo Kirsch

Publications and source records attributed to Ingo Kirsch.

At least 19 recordsLinked to original sources

arXiv2014

Chiral Ring of Strange Metals: The Multicolor Limit

The low energy limit of a dense 2D adjoint QCD is described by a family of ${\cal N}=(2,2)$ supersymmetric coset conformal field theories. In previous work we constructed chiral primaries for a small number $N < 6$ of colors. Our aim in the present note is to determine the chiral ring in the multicolor limit where $N$ is sent to infinity. We shall find that chiral primaries are labeled by partitions and identify the ring they generate as the ring of Schur polynomials. Our findings impose strong constraints on the possible dual description through string theory in an $AdS_3$ compactification.

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arXiv2014

Chiral Primaries in Strange Metals

It was suggested recently that the study of 1-dimensional QCD with fermions in the adjoint representation could lead to an interesting toy model for strange metals and their holographic formulation. In the high density regime, the infrared physics of this theory is described by a constrained free fermion theory with an emergent {\cal N}=(2,2) superconformal symmetry. In order to narrow the choice of potential holographic duals, we initiate a systematic search for chiral primaries in this model. We argue that the bosonic part of the superconformal algebra can be extended to a coset chiral algebra of the form {\cal W}_N =\SO(2N^2-2)_1/\SU(N)_{2N}. In terms of this algebra the spectrum of the low energy theory decomposes into a finite number of sectors which are parametrized by special necklaces. We compute the corresponding characters and partition functions and determine the set of chiral primaries for N \leq 5.

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arXiv2013

Chiral magnetic effect and holography

The chiral magnetic effect (CME) is a highly discussed effect in heavy-ion collisions stating that, in the presence of a magnetic field B, an electric current is generated in the background of topologically nontrivial gluon fields. We present a holographic (AdS/CFT) description of the CME in terms of a fluid-gravity model which is dual to a strongly-coupled plasma with multiple anomalous U(1) currents. In the case of two U(1) charges, one axial and one vector, the CME formally appears as a first-order transport coefficient in the vector current. We will holographically compute this coefficient at strong coupling and compare it with the hydrodynamic result. Finally, we will discuss an anisotropic variant of the model and study a possible dependence of the CME on the elliptic flow coefficient v_2.

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arXiv2012

Spin-k/2-spin-k/2 SU(2) two-point functions on the torus

We discuss a class of two-point functions on the torus of primary operators in the SU(2) Wess-Zumino-Witten model at integer level k. In particular, we construct an explicit expression for the current blocks of the spin-k/2-spin-k/2 torus two-point functions for all k. We first examine the factorization limits of the proposed current blocks and test their monodromy properties. We then prove that the current blocks solve the corresponding Knizhnik-Zamolodchikov-like differential equations using the method of Mathur, Mukhi and Sen.

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arXiv2012

Anisotropic hydrodynamics, holography and the chiral magnetic effect

We discuss a possible dependence of the chiral magnetic effect (CME) on the elliptic flow coefficient v2. We first study this in a hydrodynamic model for a static anisotropic plasma with multiple anomalous U(1) currents. In the case of two charges, one axial and one vector, the CME formally appears as a first-order transport coefficient in the vector current. We compute this transport coefficient and show its dependence on v2. We also determine the CME-coefficient from first-order corrections to the dual AdS background using the fluid-gravity duality. For small anisotropies, we find numerical agreement with the hydrodynamic result.

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arXiv2011

Worldsheet operator product expansions and p-point functions in AdS3/CFT2

We construct the operator product expansions (OPE) of the chiral primary operators in the worldsheet theory for strings on AdS_3 x S^3 x T^4. As an interesting application, we will use the worldsheet OPEs to derive a recursion relation for a particular class of extremal p-point correlators on the sphere. We compare our result with the corresponding recursion relation previously found in the symmetric orbifold theory on the boundary of AdS_3.

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arXiv2011

Fluid/gravity model for the chiral magnetic effect

We consider the STU model as a gravity dual of a strongly-coupled plasma with multiple anomalous U(1) currents. In the bulk we add additional background gauge fields to include the effects of external electric and magnetic fields on the plasma. Reducing the number of chemical potentials in the STU model to two and interpreting them as quark and chiral chemical potential, we obtain a holographic description of the chiral magnetic and chiral vortical effects (CME and CVE) in relativistic heavy ion collisions. These effects formally appear as first-order transport coefficients in the electromagnetic current. We compute these coefficients from our model using fluid/gravity duality. We also find analogous effects in the axial current. Finally, we briefly discuss a variant of our model, in which the CME/CVE is realized in the late-time dynamics of an expanding plasma.

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arXiv2010

Holographic dual of a boost-invariant plasma with chemical potential

We construct a gravity dual of a boost-invariant flow of an N=4 SU(N) supersymmetric Yang-Mills gauge theory plasma with chemical potential. We present both a first-order corrected late-time solution in Eddington-Finkelstein coordinates and a zeroth-order solution in parametric form in Fefferman-Graham coordinates. The resulting background takes the form of a time-dependent AdS Reissner-Nordstroem-type black hole whose horizons move into the bulk of the AdS space. The solution correctly reproduces the energy and charge density as well as the viscosity of the plasma previously computed in the literature.

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arXiv2010

Non-equilibrium physics at a holographic chiral phase transition

The D3/D7 system holographically describes an N=2 gauge theory which spontaneously breaks a chiral symmetry by the formation of a quark condensate in the presence of a magnetic field. At finite temperature it displays a first order phase transition. We study out of equilibrium dynamics associated with this transition by placing probe D7 branes in a geometry describing a boost-invariant expanding or contracting plasma. We use an adiabatic approximation to track the evolution of the quark condensate in a heated system and reproduce the phase structure expected from equilibrium dynamics. We then study solutions of the full partial differential equation that describes the evolution of out of equilibrium configurations to provide a complete description of the phase transition including describing aspects of bubble formation.

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arXiv2010

Worldsheet four-point functions in AdS(3)/CFT(2)

We calculate some extremal and non-extremal four-point functions on the sphere of certain chiral primary operators for strings on AdS_3 x S^3 x T^4. The computation is done for small values of the spacetime cross-ratio where global SL(2) and SU(2) descendants may be neglected in the intermediate channel. Ignoring also current algebra descendants, we find that in the non-extremal case the integrated worldsheet correlators factorize into spacetime three-point functions, which is non-trivial due to the integration over the moduli space. We then restrict to the extremal case and compare our results with the four-point correlators recently computed in the dual boundary theory. We also discuss a particular non-extremal correlator involving two chiral and two anti-chiral operators.

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arXiv2009

On the Relation between Hybrid and Pure Spinor String Theory

In this paper we revisit Berkovits' pure spinor formalism in lower dimensions. We are particularly interested in relating a six-dimensional pure spinor action previously constructed in the literature to other superstring formalisms. In order to gain some insight into six-dimensional pure spinors, we first derive their action by gauge-fixing the classical six-dimensional Green-Schwarz action. We then consider a hybrid pure spinor construction in which the spacetime symmetries of six of the ten dimensions are described in pure spinor variables, while the remaining four dimensions are parameterized in terms of RNS variables. We relate this pure spinor formalism to the Berkovits-Vafa-Witten hybrid formalism of string theory on R^6 x T^4.

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arXiv2009

A note on the holography of Chern-Simons matter theories with flavour

We study a three-dimensional N=3 U(N)_k x U(N)_{-k} Chern-Simons matter theory with flavour, corresponding to the N=6 Aharony-Bergman-Jafferis-Maldacena CSM theory coupled to 2N_f fundamental fields. The dual holographic description is given by the near-horizon geometry of N M2-branes at a particular hypertoric geometry M_8. We explicitly construct the space M_8 and match its isometries to the global symmetries of the field theory. We also discuss the model in the quenched approximation by embedding probe D6-branes in AdS_4 x CP^3.

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arXiv2008

Heterotic AdS_3/CFT_2 duality with (0,4) spacetime supersymmetry

We discuss the AdS_3/CFT_2 duality of a heterotic three-charge model with (0,4) target space supersymmetry. The worldsheet theory for heterotic strings on the AdS_3 x S^3/Z_N x T^4 near-horizon geometry was constructed by Kutasov, Larsen and Leigh in [hep-th/9812027]. We propose that the dual conformal field theory is given by a two-dimensional (0,4) sigma model arising on the Higgs branch of an orbifolded ADHM model. As a non-trivial consistency check of the correspondence, we find that the left- and right-moving central charges of the infrared conformal field theory agree with those predicted by the worldsheet model. Moreover, using the entropy function formalism, we show that to next-to-leading order the central charge can also be obtained from an alpha'-corrected supergravity theory.

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arXiv2007

Mesons in Gauge/Gravity Duals - A Review

We review recent progress in studying mesons within gauge/gravity duality, in the context of adding flavour degrees of freedom to generalizations of the AdS/CFT correspondence. Our main focus is on the `top-down approach' of considering models constructed within string theory. We explain the string-theoretical constructions in detail, aiming at non-specialists. These give rise to a new way of describing strongly coupled confining large N gauge gauge theories similar to large N QCD. In particular, we consider gravity dual descriptions of spontaneous chiral symmetry breaking, and compare with lattice results. A further topic covered is the behaviour of flavour bound states in finite temperature field theories dual to a gravity background involving a black hole. We also describe the `bottom up' phenomenological approach to mesons within AdS/QCD. -- Some previously unpublished results are also included.

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arXiv2007

Holographic heavy-light mesons from non-Abelian DBI

In the context of gauge/gravity duals with flavor, we examine heavy-light mesons which involve a heavy and a light quark. For this purpose we embed two D7 brane probes at different positions into the gravity background. We establish the non-Abelian Dirac-Born-Infeld (DBI) action for these probes, in which the U(2) matrix describing the embedding is diagonal. The fluctuations of the brane probes correspond to the mesons. In particular, the off-diagonal elements of the U(2) fluctuation matrix correspond to the heavy-light mesons, while the diagonal elements correspond to the light-light and heavy-heavy mesons, respectively. The heavy-light mesons scale differently with the 't Hooft coupling than the mesons involving quarks of equal mass. The model describes both scalar and vector mesons. For different dilaton-deformed gravity backgrounds, we also calculate the Wilson loop energy, and compare with the meson masses.

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arXiv2007

Worldsheet correlators in AdS(3)/CFT(2)

The AdS_3/CFT_2 correspondence is checked beyond the supergravity approximation by comparing correlation functions. To this end we calculate 2- and 3-point functions on the sphere of certain chiral primary operators for strings on AdS_3 x S^3 x T^4. These results are then compared with the corresponding amplitudes in the dual 2-dimensional conformal field theory. In the limit of small string coupling, where the sphere diagrams dominate the string perturbation series, beautiful agreement is found.

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arXiv2006

Spectroscopy of fermionic operators in AdS/CFT

We compute the spectrum of color-singlet fermionic operators in the N=2 gauge theory on intersecting D3 and D7-branes using the AdS/CFT correspondence. The operator spectrum is found analytically by solving the equations for the dual D7-brane fluctuations. For the fermionic part of the D7-brane action, we use the Dirac-like form found by Martucci et al. (hep-th/0504041). We also consider the baryon spectrum of a large class of supersymmetric gauge theories using a phenomenological approach to the gauge/gravity duality.

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arXiv2006

A Higgs Mechanism for Gravity. Part II: Higher Spin Connections

We continue the work of hep-th/0503024 in which gravity is considered as the Goldstone realization of a spontaneously broken diffeomorphism group. We complete the discussion of the coset space Diff(d,R)/SO(1,d-1) formed by the d-dimensional group of analytic diffeomorphisms and the Lorentz group. We find that this coset space is parameterized by coordinates, a metric and an infinite tower of higher-spin-like or generalized connections. We then study effective actions for the corresponding symmetry breaking which gives mass to the higher spin connections. Our model predicts that gravity is modified at high energies by the exchange of massive higher spin particles.

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