arXiv subjects

Barak Kol

Publications and source records attributed to Barak Kol.

76 records · Page 5Linked to original sources

arXiv1997

5d Field Theories and M Theory

5-brane configurations describing 5d field theories are promoted to an M theory description a la Witten in terms of polynomials in two complex variables. The coefficients of the polynomials are the Coulomb branch. This picture resolves apparent singularities at vertices and reveals exponentially small corrections. These corrections ask to be compared to world line instanton corrections. From a different perspective this procedure may be used to define a diagrammatic representation of polynomials in two variables.

hep-th↗

arXiv1996

Fixed Scalars and Suppression of Hawking Evaporation

For an extreme charged black hole some scalars take on a fixed value at the horizon determined by the charges alone. We call them fixed scalars. We find the absorption cross section for a low frequency wave of a fixed scalar to be proportional to the square of the frequency. This implies a strong suppression of the Hawking radiation near extremality. We compute the coefficient of proportionality for a specific model.

hep-th↗

arXiv1996

Moduli, Scalar Charges, and the First Law of Black Hole Thermodynamics

We show that under variation of moduli fields $ϕ$ the first law of black hole thermodynamics becomes $dM = {κdA\over 8π} + ΩdJ + ψdq + χdp - Σdϕ$, where $Σ$ are the scalar charges. We also show that the ADM mass is extremized at fixed $A$, $J$, $(p,q)$ when the moduli fields take the fixed value $ϕ_{\rm fix}(p,q)$ which depend only on electric and magnetic charges. It follows that the least mass of any black hole with fixed conserved electric and magnetic charges is given by the mass of the double-extreme black hole with these charges. Our work allows us to interpret the previously established result that for all extreme black holes the moduli fields at the horizon take a value $ϕ= ϕ_{\rm fix}(p,q)$ depending only on the electric and magnetic conserved charges: $ ϕ_{\rm fix}(p,q)$ is such that the scalar charges $Σ( ϕ_{\rm fix}, (p,q))=0$.

hep-th↗

arXiv1996

E(7) Symmetric Area of the Black Hole Horizon

Extreme black holes with 1/8 of unbroken N=8 supersymmetry are characterized by the non-vanishing area of the horizon. The central charge matrix has four generic eigenvalues. The area is proportional to the square root of the invariant quartic form of $E_{7(7)}$. It vanishes in all cases when 1/4 or 1/2 of supersymmetry is unbroken. The supergravity non-renormalization theorem for the area of the horizon in N=8 case protects the unique U-duality invariant.

hep-th↗