Browsing by Author "Milanesi, Giuseppe"

Now showing 1 - 3 of 3
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    1/8 BPS States in Ads/CFT
    (2006-11-09T11:36:47Z) Gava, Edi; Milanesi, Giuseppe; Narain, Kumar S.; O'Loughlin, Martin; Physics; Elementary Particle Theory
    We study a class of exact supersymmetric solutions of type IIB Supergravity. They have an SO(4) x SU(2) x U(1) isometry and preserve generically 4 of the 32 supersymmetries of the theory. Asymptotically AdS_5 x S^5 solutions in this class are dual to 1/8 BPS chiral operators which preserve the same symmetries in the N=4 SYM theory. They are parametrized by a set of four functions that satisfy certain differential equations. We analyze the solutions to these equations in a large radius asymptotic expansion: they carry charges with respect to two U(1) KK gauge fields and their mass saturates the expected BPS bound.
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    Aspects of Finite Temperature Quantum Field Theory in a Black Hole Background
    (2005) Milanesi, Giuseppe; Mintchev, Mihail; Physics; Elementary Particle Theory
    We quantize a scalar field at finite temperature T in the background of a classical black hole, adopting 't Hooft's "brick wall" model with generic mixed boundary conditions at the brick wall boundary. We first focus on the exactly solvable case of two dimensional space-time. As expected, the energy density is integrable in the limit of vanishing brick wall thickness only for T = TH - the Hawking temperature. Consistently with the most general stress energy tensor allowed in this background, the energy density shows a surface contribution localized on the horizon. We point out that the usual divergences occurring in the entropy of the thermal atmosphere are due to the assumption that the third law of thermodynamics holds for the quantum field in the black hole background. Such divergences can be avoided if we abandon this assumption. The entropy density also has a surface term localized on the horizon, which is open to various interpretations. The extension of these results to higher space-time dimensions is briefly discussed.
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    Singularities and Closed Timelike Curves in type IIB 1/2 BPS Geometries
    (2005) Milanesi, Giuseppe; O'Loughlin, Martin; Physics; Elementary Particle Theory
    We study in detail the moduli space of solutions discovered in LLM relaxing the constraint that guarantees the absence of singularities. The solutions fall into three classes, non-singular, null-singular and time machines with a time-like naked singularity. We study the general features of these metrics and prove that there are actually just two generic classes of space-times - those with null singularities are in the same class as the non-singular metrics. AdS/CFT seems to provide a dual description only for the first of these two types of space-time in terms of a unitary CFT indicating the possible existence of a chronology protection mechanism for this class of geometries.