arXiv subjects

Edi Halyo

Publications and source records attributed to Edi Halyo.

At least 55 records · Page 3Linked to original sources

arXiv2001

Universal Counting of Black Hole Entropy by Strings on the Stretched Horizon

We show that the entropy of any black object in any dimension can be understood as the entropy of a highly excited string on the stretched horizon. The string has a gravitationally renormalized tension due to the large redshift near the horizon. The Hawking temperature is given by the Hagedorn temperature of the string. As examples, we consider black holes with one (black p-branes) or two charges, Reissner-Nordstrom black holes and the BTZ black hole in addition to Schwarzschild black holes. We show that the vanishing and nonvanishing extremal entropies can be obtained as smooth limits of the near-extreme cases.

hep-th↗

arXiv2001

De Sitter Entropy and Strings

We show that the entropy of de Sitter space in any dimension can be understood as the entropy of a highly excited string located near the horizon. The string tension is renormalized to $T \sim Λ$ due to the large gravitational redshift near the horizon. The de Sitter temperature is given by the Hagedorn temperature of the string.

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arXiv2001

Hybrid Quintessence with an End or Quintessence from Branes and Large Dimensions

We describe a model of hybrid quintessence in which in addition to the tracker field there is a trigger field which is responsible for ending quintessence. As a result, hybrid quintessence does not suffer from the problems associated with the eternal acceleration of the universe. We derive the hybrid quintessence potential on branes from the interbrane interaction in string theory and show that it requires TeV scale strings and two millimeter size dimensions. This scenario predicts a dark energy density of $O(mm^{-4})$ and relates the smallness of this energy to the large size of the extra dimensions.

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arXiv2001

Inflation from Rotation

We obtain brane inflation in configurations with Dp and D(p-2) branes which are far apart and almost perpendicular to each other. Chaotic brane inflation occurs when the branes can only rotate with the inflaton given by the angle between the branes. When the branes can also move hybrid brane inflation occurs where the inflaton is the distance between the branes and the trigger field is related to the angle. In both models we find a spectral index very close to one. Both types of inflation require $M_s \sim 10^{16-17} GeV$ with one large radius of size $1/R \sim 10^{12-15} GeV$.

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arXiv1999

Localized Gravity on Branes in anti-de Sitter Spaces

We discuss the conditions under which 4D gravity is localized on domain walls in 5D anti-de Sitter spaces. Our approach is based on considering the limits in which the localized gravity decouples. We find that gravity is localized if the wall is located a finite distance from the boundary of the anti-de Sitter space and has a finite tension. In addition, it has to be a $δ$-function source of gravity.

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arXiv1999

D--term Inflation at the TeV Scale and Large Internal Dimensions

We show that D--term inflation at the TeV scale is possible in the presence of large internal dimensions. This requires very small couplings and masses which arise from the large size of the compact dimensions. We show that acceptable number of e-folds, magnitude and spectrum of density perturbations $δρ/ρ$ and $η$ can be obtained in this scenario at the price of a reheating temperature which is too high. Demanding an acceptable $T_R$ results in very small density perturbations.

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arXiv1999

Late D-term Inflation and the Cosmological Moduli Problem in TeV Scale Strings

We show that a short period of late D-term inflation can solve the cosmological moduli (radion) problem of (asymmetric) inflation at the TeV scale. Late inflation happens after the large compact dimensions are stabilized which is crucial for obtaining the extremely small Hubble constant and inflaton mass required.

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arXiv1999

Mirage Gauge Coupling Unification and TeV Scale Strings

We consider gauge coupling unification in models with TeV scale strings and large compact dimensions realized as type IIB string orientifolds. Following an observation by Ibanez we show that the gauge couplings at low energies can behave as if they effectively unify at $M_U \sim 2 \times 10^{16} GeV$ with $α_U \sim 1/24$. This requires the $σ$ model anomaly coefficients $b_a^{i'}$ not to be all equal and their ratio to the $β$-functions of minimally supersymmetric Standard Model $β_a$ to be a constant independent of the gauge group. If, in addition, $b_a^{i'}$ have a gauge group independent constant piece the relation between the unified gauge coupling and the dilaton VEV is modified so that there can be weakly coupled gauge theories arising from strongly coupled strings.

hep-ph↗

arXiv1999

Moduli Forces in String Models with Large Internal Dimensions

We estimate the strength and range of forces mediated by string moduli in type I string models with two (or more) large internal dimensions. We find that forces mediated by twisted moduli which live on the brane world--volume can mediate forces which are orders of magnitude stronger than gravity with a range up to a milimeter. If they exist, these forces can be easily observed in present experiments. On the other hand, forces mediated by the dilaton and untwisted moduli are about a hundred times stronger than gravity and may be observed depending on their range.

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arXiv1999

D-term Inflation in Type I String Theory

D-term inflation realized in heterotic string theory has two problems: the scale of the anomalous D-term is too large for accounting for COBE data and the coupling constant of the anomalous U(1) is too large for supergravity to be valid. We show that both of these problems can be easily solved in D-term inflation based on type I string theory or orientifolds of type IIB strings.

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arXiv1998

Supergravity on $AdS_{4/7} \times S^{7/4}$ and M Branes

We calculate the dimensions of operators in three and six dimensional superconformal field theories by using the duality between these theories at large N and D=11 supergravity on $AdS_{4/7} \times S^{7/4}$. We find that for the duality relations to work the Kaluza--Klein masses given in the supergravity literature must be rescaled and/or shifted.

hep-th↗

arXiv1998

Supergravity on $AdS_{5/4} \times$ Hopf Fibrations and Conformal Field Theories

We obtain three and four dimensional conformal field theories with less than maximal supersymmetry by using their supergravity duals. These supergravity theories are type II on $AdS_5 \times CP^2$, IIA on $AdS_4 \times CP^3$, IIB on $AdS_5 \times S^5/Z_k$ and D=11 supergravity on $AdS_4 \times S^7/Z_k$. They are obtained from the spherically compactified ten and eleven dimensional theories by either Hopf reduction or by winding the U(1) fiber over the base.

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arXiv1997

Six Dimensional Schwarzschild Black Holes in M(atrix) Theory

We calculate the entropy of six dimensional Schwarzschild black holes in matrix theory. We use the description of the matrix model on $T^5$ as the world-volume theory of NS five-branes and show that the black hole entropy is reproduced by noncritical closed strings with fractional tension living on the five-brane.

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arXiv1997

M(atrix) Black Holes in Five Dimensions

We examine five dimensional extreme black holes with three charges in the matrix model. We build configurations of the 5+1 super Yang-Mills theory which correspond to black holes with transverse momentum charge. We calculate their mass and entropy from the super Yang-Mills theory and find that they match the semi-classical black hole results. We extend our results to nonextreme black holes in the dilute gas approximation.

hep-th↗

arXiv1997

A Proposal for the Wrapped Transverse Five Brane in M(atrix) Theory

We propose a state in 5+1 super Yang-Mills theory which corresponds to the wrapped transverse five brane of M(atrix) theory on $T^5$. This state is a magnetic flux quantized in units of $1/g_6^2$ through a plane defined by one side of the box and a new direction which is not manifest.

hep-th↗

arXiv1996

Four Dimensional Black Holes and Strings with Rescaled Tension

We give a microscopic description of extreme and near-extreme Reissner-Nordstrom black holes in four dimensions in terms of fundamental strings in a background of magnetic five branes and monopoles. The string oscillator numbers and tension are rescaled due to the Rindler space background with the string mass fixed. The entropy of the black holes is reproduced correctly by that of the string with the tension rescaling taken into account.

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arXiv1996

Reissner-Nordstrom Black Holes and Strings with Rescaled Tension

We show that extreme and nonextreme Reissner--Nordstrom black holes in five dimensions can be described by closed fundamental strings with two charges in a magnetic five brane. Due to the five brane background the string oscillator number and tension are rescaled whereas the mass remains fixed. The black hole mass is given by the sum of the five brane and string masses. Its entropy however is given by only that of the string with the tension rescaling taken into account. We also show that the emission of a low energy scalar from the slightly nonextreme string matches the Hawking radiation expected from the black hole.

hep-th↗

arXiv1996

Hybrid Inflation from Supergravity D Terms

We argue that the mass of the inflaton can be much smaller than the Hubble constant in supergravity models in which inflation is driven by D--terms and not F--terms. We investigate a supergravity toy model which leads to hybrid inflation due to an anomalous D--term. We show that the slow--roll condition can be satisfied and the correct magnitude for density perturbations can be obtained for some choice of model parameters. The kind of model considered can naturally arise in some string derived supergravity models.

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