arXiv subjects

Horatiu Nastase

Publications and source records attributed to Horatiu Nastase.

At least 73 records · Page 4Linked to original sources

arXiv2017

Penrose limits and spin chains in the GJV/CS-SYM duality

We examine Penrose limits of the duality proposed by Guarino, Jafferis and Varela between a type IIA massive background of the type of a warped, squashed $AdS_4\times S^6$, and a 2+1 dimensional IR fixed point of ${\cal N}=8$ super Yang-Mills deformed by Chern-Simons terms to ${\cal N}=2$ supersymmetry. One type of Penrose limit for closed strings corresponds to a large charge closed spin chain, and another, for open strings on giant graviton D-branes, corresponds to an open spin chain on sub-determinant operators. For the first limit, we find that like in the ABJM case, there are functions $f_a(λ)$ that interpolate between the perturbative and nonperturbative (string) regions for the magnon energy. For the second, we are unable to match the gravity result with the expected field theory result, making this model more interesting than ones with more supersymmetry.

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arXiv2017

Knotted solutions, from electromagnetism to fluid dynamics

Knotted solutions to electromagnetism and fluid dynamics are investigated, based on relations we find between the two subjects. We can write fluid dynamics in electromagnetism language, but only on an initial surface, or for linear perturbations, and we use this map to find knotted fluid solutions, as well as new electromagnetic solutions. We find that knotted solutions of Maxwell electromagnetism are also solutions of more general nonlinear theories, like Born-Infeld, and including ones which contain quantum corrections from couplings with other modes, like Euler-Heisenberg and string theory DBI. Null configurations in electromagnetism can be described as a null pressureless fluid, and from this map we can find null fluid knotted solutions. A type of nonrelativistic reduction of the relativistic fluid equations is described, which allows us to find also solutions of the (nonrelativistic) Euler's equations.

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arXiv2017

Vortices with source, FQHE and nontrivial statistics in 2+1 dimensions

We investigate vortex soliton solutions in 2+1 dimensional scalar gauge theories, in the presence of source terms in the action. Concretely, this would be applied to anyons, as well as the Fractional Quantum Hall Effect (FQHE). We classify solitons for renormalizable potentials, as well as some nonrenormalizable examples that could be relevant for the FQHE. The non-Abelian case, specifically for theories with global non-Abelian symmetries, is also investigated, as is the non-relativistic limit of the above theories, when we get a modification of the Jackiw-Pi model, with an interesting new vortex solution. We explore the application to the ABJM model, as well as more general SYM-CS models in 2+1 dimensions.

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arXiv2017

Knotted solutions for linear and nonlinear theories: electromagnetism and fluid dynamics

We examine knotted solutions, the most simple of which is the "Hopfion", from the point of view of relations between electromagnetism and ideal fluid dynamics. A map between fluid dynamics and electromagnetism works for initial conditions or for linear perturbations, allowing us to find new knotted fluid solutions. Knotted solutions are also found to to be solutions of nonlinear generalizations of electromagnetism, and of quantum-corrected actions for electromagnetism coupled to other modes. For null configurations, electromagnetism can be described as a null pressureless fluid, for which we can find solutions from the knotted solutions of electromagnetism. We also map them to solutions of Euler's equations, obtained from a type of nonrelativistic reduction of the relativistic fluid equations.

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arXiv2017

Observables in the Guarino-Jafferis-Varela/CS-SYM duality

We study various semiclassical observables in the duality proposed by Guarino, Jafferis and Varela, between a warped $AdS_4\times$ squashed $S^6$ gravitational solution and a 3 dimensional ${\cal N}=2$ SYM-CS$_k$ conformal gauge theory, deformed from the maximal $SU(N)$ ${\cal N}=8$ SYM. Baryon vertices corresponding to particle-like branes have unusual behaviour with $N$ and $k$ and present strong evidence for a certain level-rank duality. Wilson loops and the anomalous dimensions of operators of high spin scale like $(N/k)^{3/2}$. The entanglement entropy behaves like in a usual CFT. Giant magnon operators obey the same law as in 4 dimensional ${\cal N}=4$ SYM, and giant gravitons are also sub-determinant operators.

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arXiv2017

Deriving three-dimensional bosonization and the duality web

Recently, a duality web for three dimensional theories with Chern-Simons terms was proposed. This can be derived from a single bosonization type duality, for which various supporting arguments (but not a proof) were given. Here we explicitly derive this bosonization, in the Abelian case and for a particular regime of parameters. To do this, we use the particle-vortex duality in combination with a Buscher-like duality (both considered in the regime of low energies). As a corollary, Son's conjectured duality is derived in a somewhat singular limit of vanishing mass.

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arXiv2017

Particle-vortex duality in topological insulators and superconductors

We investigate the origins and implications of the duality between topological insulators and topological superconductors in three and four spacetime dimensions. In the latter, the duality transformation can be made at the level of the path integral in the standard way, while in three dimensions, it takes the form of "self-duality in odd dimensions". In this sense, it is closely related to the particle-vortex duality of planar systems. In particular, we use this to elaborate on Son's conjecture that a three dimensional Dirac fermion that can be thought of as the surface mode of a four dimensional topological insulator is dual to a composite fermion.

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arXiv2016

Small field inflation in ${\cal N}=1$ supergravity with a single chiral superfield

We consider "new inflation" inflationary models at small fields, embedded in minimal ${\cal N}=1$ supergravity with a single chiral superfield. Imposing a period of inflation compatible with experiment severely restricts possible models, classified in perturbation theory. If moreover we impose that the field goes to large values and very small potential at the current time, like would be needed for instance for the inflaton being the volume modulus in large extra dimensional scenarios, the possible models are restricted to very contrived superpotentials.

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arXiv2016

Quantum gravity and the holographic dark energy cosmology

The holographic dark energy model is obtained from a cosmological constant generated by generic quantum gravity effects giving a minimum length. By contrast, the usual bound for the energy density to be limited by the formation of a black hole simply gives the Friedmann equation. The scale of the current cosmological constant relative to the inflationary scale is an arbitrary parameter characterizing initial conditions, which however can be fixed by introducing a physical principle during inflation, as a function of the number of e-folds and the inflationary scale.

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arXiv2015

A nonabelian particle-vortex duality in gauge theories

We define a nonabelian version of particle-vortex duality, by dimensionally extending usual (1+1)-dimensional nonabelian T-duality to (2+1) dimensions. While we will explicitly describe a global $SU(2)$ symmetry, our methods can also be applied to a larger group $G$, by gauging an appropriate subgroup. We will exemplify our duality with matter in both adjoint and fundamental representations by considering a modification of ${\cal N}=2$ supersymmetric Yang-Mills theory (Seiberg-Witten theory reduced to (2+1) dimensions), and an $SU(2)\times U(1)$ color-flavor locked theory that exhibits nonabelian vortex solutions.

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arXiv2015

DBI scalar field theory for QGP hydrodynamics

A way to describe the hydrodynamics of the quark-gluon plasma using a DBI action is proposed, based on the model found by Heisenberg for high energy scattering of nucleons. The expanding plasma is described as a shockwave in a DBI model for a real scalar standing in for the pion, and I show that one obtains a fluid description in terms of a relativistic fluid that near the shock is approximately ideal ($η\simeq 0$) and conformal. One can introduce an extra term inside the square root of the DBI action that generates a shear viscosity term in the energy-momentum tensor near the shock, as well as a bulk viscosity, and regulates the behaviour of the energy density at the shock, making it finite. The resulting fluid satisfies the relativistic Navier-Stokes equation with $u^μ, ρ,P,η$ defined in terms of $ϕ$ and its derivatives. One finds a relation between the parameters of the theory and the QGP thermodynamics, $\a/\b^2=η/(sT)$, and by fixing $\a$ and $\b$ from usual (low multiplicity) particle scattering, one finds $T\propto m_π$.

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arXiv2015

Nonrelativistic limit of the abelianized ABJM model and the ADS/CMT correspondence

We consider the nonrelativistic limit of the abelian reduction of the massive ABJM model proposed in \cite{Mohammed:2012gi}, obtaining a supersymmetric version of the Jackiw-Pi model. The system exhibits an ${\cal N}=2$ Super-Schrödinger symmetry with the Jackiw-Pi vortices emerging as BPS solutions. We find that this $(2+1)$-dimensional abelian field theory is dual to a certain (3+1)-dimensional gravity theory that differs somewhat from previously considered abelian condensed matter stand-ins for the ABJM model. We close by commenting on progress in the top-down realization of the AdS/CMT correspondence in a critical string theory.

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arXiv2015

A Nonabelian Particle-Vortex Duality

We define a nonabelian particle-vortex duality as a $3-$dimensional analogue of the usual $2-$dimensional worldsheet nonabelian T-duality. The transformation is defined in the presence of a global $SU(2)$ symmetry and, although derived from a string theoretic setting, we formulate it generally. We then apply it to so-called "semilocal strings" in an $SU(2)_{G}\times U(1)_{L}$ gauge theory, originally discovered in the context of cosmic string physics.

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arXiv2015

Non-Abelian T-duality for nonrelativistic holographic duals

We find new type II backgrounds with non-relativistic symmetries via non-Abelian T-duality. First we consider geometries with Galilean symmetries in type IIA, which have been identified as non-relativistic generalizations of the ABJM background and massive IIA supergravities. We then consider the non-Abelian T-duality transformation on the backgrounds with Lifshitz symmetry constructed by Donos and Gauntlett. Using gauge/gravity duality we study aspects of the field theory dual to these backgrounds.

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arXiv2015

General $f(R)$ and conformal inflation from minimal supergravity plus matter

We embed general $f(R)$ inflationary models in minimal supergravity plus matter, a single chiral superfield $Φ$, with or without another superfield $S$, via a Jordan frame Einstein+scalar description. In particular, inflationary models like a generalized Starobinsky one are analyzed and constraints on them are found. We also embed the related models of conformal inflation, also described as Jordan frame Einstein+scalar models, in particular the conformal inflation from the Higgs model, and analyze the inflationary constraints on them.

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arXiv2015

Massive ABJM and black hole entropy in the presence of field strength coupling to curvature

Assuming that the near horizon geometry of the black hole solution of the gravity dual to the ABJM model, in the presence of a coupling between the Weyl tensor and the field strength, is $AdS_{2}\times S^{2}$, we compute Sen's entropy function for this theory. By extremizing the entropy function we write a formula for the entropy of the black hole, and then we compute the same entropy using Wald's formula and show that the results are the same. In this way we generalize the calculation of black hole entropy to cases of curvature coupling to the field strength, including at first order, and we also show how to calculate the black hole entropy when the black hole solution is unknown, from just a few simple assumptions about the horizon.

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arXiv2015

On $\mathcal{N}=1$ susy backgrounds with $AdS$ factor from nonabelian T-duality

We consider the action of a non-abelian T-duality on backgrounds with an AdS${}_5$ factor in type IIA supergravity, finding a new type IIB background, as well as the non-abelian T-dual of a domain wall solution which has as limits the non-abelian T-dual of $AdS_5\times T^{1,1}$ and the non-abelian T-dual of $AdS_3\times \mathbb{R}^2\times S^2\times S^3$. We explore some consequences of non-abelian T-duality for the dual conformal field theories.

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arXiv2015

A natural cosmological constant from chameleons

We present a simple model where the effective cosmological constant appears from chameleon scalar fields. For a Kachru-Kallosh-Linde-Trivedi (KKLT)-inspired form of the potential and a particular chameleon coupling to the local density, patches of approximately constant scalar field potential cluster around regions of matter with density above a certain value, generating the effect of a cosmological constant on large scales. This construction addresses both the cosmological constant problem (why $Λ$ is so small, yet nonzero) and the coincidence problem (why $Λ$ is comparable to the matter density now).

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