arXiv subjects

Micha Berkooz

Publications and source records attributed to Micha Berkooz.

At least 55 records · Page 3Linked to original sources

arXiv2008

Weakly Renormalized Near 1/16 SUSY Fermi Liquid Operators in N = 4 SYM

We discuss a class of Fermi Liquid Operators in N = 4 SYM. We show that these operators are eigenstates of the full quantum dilatation operator. We compute their 1 and 2 loop anomalous dimensions, and show that, similar to Fermi liquids in condensed matter systems, these corrections are suppressed by an arbitrarily small parameter, which is the equivalent of one over the Fermi energy. These operators are, at the classical level, descendants of 1/16 BPS operators, with some scaling properties similar to those of the 1/16 Black Holes in AdS_5.

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arXiv2008

Non-Abelian structures in compactifications of M-theory on seven-manifolds with SU(3) structure

We study M-theory compactified on a specific class of seven-dimensional manifolds with SU(3) structure. The manifolds can be viewed as a fibration of an arbitrary Calabi-Yau threefold over a circle, with a U-duality twist around the circle. In some cases we find that in the four dimensional low energy effective theory a (broken) non-Abelian gauge group appears. Furthermore, such compactifications are shown to be dual to previously analyzed compactifications of the heterotic string on K3 x T^2, with background gauge field fluxes on the T^2.

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arXiv2008

On the Conformal Field Theory Duals of type IIA AdS_4 Flux Compactifications

We study the conformal field theory dual of the type IIA flux compactification model of DeWolfe, Giryavets, Kachru and Taylor, with all moduli stabilized. We find its central charge and properties of its operator spectrum. We concentrate on the moduli space of the conformal field theory, which we investigate through domain walls in the type IIA string theory. The moduli space turns out to consist of many different branches. We use Bezout's theorem and Bernstein's theorem to enumerate the different branches of the moduli space and estimate their dimension.

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arXiv2007

Thermal AdS(3), BTZ and competing winding modes condensation

We study the thermal physics of AdS(3) and the BTZ black hole when embedded in String theory. The exact calculation of the Hagedorn temperature in TAdS(3) is reinterpreted as the appearance of a winding tachyon both in AdS(3) and BTZ. We construct a dual framework for analyzing the phases of the system. In this dual framework, tachyon condensation and geometric capping appear on the same footing, bridging the usual gap of connecting tachyon condensation to modifications of geometry. This allows us to construct in a natural way a candidate for the unstable phase, analogous to a small black hole in higher dimensions. Additional peculiar effects associated with the Hagedorn temperature and the Hawking-Page transition, some to do with the asymptotic structure of AdS(3) and some with strong curvature effects, are analyzed and explained.

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arXiv2007

A Short Review of Time Dependent Solutions and Space-like Singularities in String Theory

These lecture notes provide a short review of the status of time dependent backgrounds in String theory, and in particular those that contain space-like singularities. Despite considerable efforts, we do not have yet a full and compelling picture of such backgrounds. We review some of the various attempts to understand these singularities via generalizations of the BKL dynamics, using worldsheet methods and using non-perturbative tools such as the AdS/CFT correspondence and M(atrix) theory. These lecture notes are based on talks given at Cargese 06 and the dead-sea conference 06.

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arXiv2006

A Fermi Surface Model for Large Supersymmetric AdS_5 Black Holes

We identify a large family of 1/16 BPS operators in N=4 SYM that qualitatively reproduce the relations between charge, angular momentum and entropy in regular supersymmetric AdS_5 black holes when the main contribution to their masses is given by their angular momentum.

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arXiv2005

High Density Preheating Effects on Q-ball Decays and MSSM Inflation

Non-perturbative preheating decay of post-inflationary condensates often results in a high density, low momenta, non-thermal gas. In the case where the non-perturbative classical evolution also leads to Q-balls, this effect shields them from instant dissociation, and may radically change the thermal history of the universe. For example, in a large class of inflationary scenarios, motivated by the MSSM and its embedding in string theory, the reheat temperature changes by a multiplicative factor of $10^{12}$.

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arXiv2005

Non-Local Effects of Multi-Trace Deformations in the AdS/CFT Correspondence

The AdS/CFT correspondence relates deformations of the CFT by "multi-trace operators" to "non-local string theories". The deformed theories seem to have non-local interactions in the compact directions of space-time; in the gravity approximation the deformed theories involve modified boundary conditions on the fields which are explicitly non-local in the compact directions. In this note we exhibit a particular non-local property of the resulting space-time theory. We show that in the usual backgrounds appearing in the AdS/CFT correspondence, the commutator of two bulk scalar fields at points with a large enough distance between them in the compact directions and a small enough time-like distance between them in AdS vanishes, but this is not always true in the deformed theories. We discuss how this is consistent with causality.

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arXiv2005

Flow of Geometries and Instantons on the Null Orbifold

We study condensation of twisted sector states in the null orbifold geometry. As the singularity is time-dependent, we probe it using D-Instantons. We present evidence that the null-orbifold flows to the $Z_N$ orbifold. We also comment on the subtleties of quantizing the closed superstring in this background.

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arXiv2005

Open String Moduli in KKLT Compactifications

In the Kachru-Kallosh-Linde-Trivedi (KKLT) de-Sitter construction one introduces an anti-D3-brane that breaks the supersymmetry and leads to a positive cosmological constant. In this paper we investigate the open string moduli associated with this anti-D3-brane, corresponding to its position on the 3-sphere at the tip of the deformed conifold. We show that in the KKLT construction these moduli are very light, and we suggest a possible way to give these moduli a large mass by putting orientifold planes in the KKLT "throat".

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arXiv2005

Constraining Modular Inflation in the MSSM from Giant Q-Ball Formation

We discuss constraints on which flat directions can have large vacuum expectation values (VEVs) after inflation. We show that only flat directions which are not charged under B-L and develop positive pressure due to renormalization group effects can have large VEVs of order $\Mp$. For example, within the MSSM only the $H_uH_d$ flat direction is found to be viable. This strongly constrains the embedding of a broad class of inflationary models in the MSSM or some other supersymmetric extension of the SM. For flat directions with negative pressure, the condensate fragments into very large Q-balls which we call Q-giants. We discuss the formation, evolution and reheating of these Q-giants and show that they decay too late. The analysis requires taking into account new phases of the flat directions, which have been overlooked in the formation and dynamics of the Q-balls. These constraints may be ameliorated by invoking a short period of thermal inflation. The latter, however, is viable in a very narrow window of parameter space and requires fine tuning.

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arXiv2004

Hybrid Inflation and the Moduli Problem

We revisit some questions in supersymmetric hybrid inflation (SHI). We analyze the amount of fine tuning required in various models, the problem of decay at the end of inflation and the generation of baryons after inflation. We find that the most natural setting for HI is in supersymmetric models with non-renormalizable couplings. Furthermore, we argue that almost inevitably, one of the fields involved is a modulus, with Planck scale variation. The resulting moduli problem can be solved in two ways: either by a massive modulus (which requires some fine tuning), or an enhanced symmetry point, in which the moduli becomes strongly coupled to the Standard Model. Various possibilities for baryon production are discussed.

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arXiv2004

Baryogenesis from the Kobayashi-Maskawa Phase

The Standard Model fulfills the three Sakharov conditions for baryogenesis. The smallness of quark masses suppresses, however, the CP violation from the Kobayashi-Maskawa phase to a level that is many orders of magnitude below what is required to explain the observed baryon asymmetry. We point out that if, as a result of time variation in the Yukawa couplings, quark masses were large at the time of the electroweak phase transition, then the Kobayashi-Maskawa mechanism could be the source of the asymmetry. The Froggatt-Nielsen mechanism provides a plausible framework where the Yukawa couplings could all be of order one at that time, and settle to their present values before nucleosynthesis. The problems related to a strong first order electroweak phase transition may also be alleviated in this framework. Our scenario reveals a loophole in the commonly held view that the Kobayashi-Maskawa mechanism cannot be the dominant source of CP violation to play a role in baryogenesis.

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arXiv2002

Comments on Cosmological Singularities in String Theory

We compute string scattering amplitudes in an orbifold of Minkowski space by a boost, and show how certain divergences in the four point function are associated with graviton exchange near the singularity. These divergences reflect large tree-level backreaction of the gravitational field. Near the singularity, all excitations behave like massless fields on a 1+1 dimensional cylinder. For excitations that are chiral near the singularity, we show that divergences are avoided and that the backreaction is milder. We discuss the implications of this for some cosmological spacetimes. Finally, in order to gain some intuition about what happens when backreaction is taken into account, we study an open string rolling tachyon background as a toy model that shares some features with R^{1,1}/Z.

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arXiv2002

"Holey Sheets" - Pfaffians and Subdeterminants as D-brane Operators in Large N Gauge Theories

In the AdS/CFT correspondence, wrapped D3-branes (such as "giant gravitons") on the string theory side of the correspondence have been identified with Pfaffian, determinant and subdeterminant operators on the field theory side. We substantiate this identification by showing that the presence of pairs of such operators in a correlation function of a large N gauge theory naturally leads to a modified 't Hooft expansion including also worldsheets with boundaries. This happens independently of supersymmetry or conformal invariance.

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arXiv2002

Double Trace Deformations, Infinite Extra Dimensions and Supersymmetry Breaking

It was recently shown how to break supersymmetry in certain $AdS_3$ spaces, without destabilizing the background, by using a ``double trace'' deformation which localizes on the boundary of space-time. By viewing spatial sections of $AdS_3$ as a compactification space, one can convert this into a SUSY breaking mechanism which exists uniformly throughout a large 3+1 dimensional space-time, without generating any dangerous tadpoles. This is a generalization of a Visser type infinite extra dimensions compactification. Although the model is not Lorentz invariant, the dispersion relation is relativistic at high enough momenta, and it can be arranged such that at the same kinematical regime the energy difference between between former members of a SUSY multiplet is large.

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arXiv2002

"Double-trace" Deformations, Boundary Conditions and Spacetime Singularities

Double-trace deformations of the AdS/CFT duality result in a new perturbation expansion for string theory, based on a non-local worldsheet. We discuss some aspects of the deformation in the low energy gravity approximation, where it appears as a change in the boundary condition of fields. We relate unique features of the boundary of AdS to the worldsheet becoming non-local, and conjecture that non-local worldsheet actions may be generic in other classes of backgrounds.

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arXiv2001

Non-local string theories on AdS_3 times S^3 and stable non-supersymmetric backgrounds

We exhibit a simple class of exactly marginal "double-trace" deformations of two dimensional CFTs which have AdS_3 duals, in which the deformation is given by a product of left and right-moving U(1) currents. In this special case the deformation on AdS_3 is generated by a local boundary term in three dimensions, which changes the physics also in the bulk via bulk-boundary propagators. However, the deformation is non-local in six dimensions and on the string worldsheet, like generic non-local string theories (NLSTs). Due to the simplicity of the deformation we can explicitly make computations in the non-local string theory and compare them to CFT computations, and we obtain precise agreement. We discuss the effect of the deformation on closed strings and on D-branes. The examples we analyze include a supersymmetry-breaking but exactly marginal "double-trace" deformation, which is dual to a string theory in which no destabilizing tadpoles are generated for moduli nonperturbatively in all couplings, despite the absence of supersymmetry. We explain how this cancellation works on the gravity side in string perturbation theory, and also non-perturbatively at leading order in the deformation parameter. We also discuss possible flat space limits of our construction.

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