Greybody Factors and Charges in Kerr/CFT

We compute greybody factors for near extreme Kerr black holes in D=4 and D=5. In D=4 we include four charges so that our solutions can be continuously deformed to the BPS limit. In D=5 we include two independent angular momenta so Left-Right symmetry is incorporated. We discuss the CFT interpretation of our emission amplitudes, including the overall frequency dependence and the dependence on all black hole parameters. We find that all additional parameters can be incorporated Kerr/CFT, with central charge independent of U(1) charges.Comment: 27 pages. v2: typos fixed, references adde

Open String Fluctuations in AdS with and without Torsion

The equations of motion and boundary conditions for the fluctuations around a classical open string, in a curved space-time with torsion, are considered in compact and world-sheet covariant form. The rigidly rotating open strings in Anti de Sitter space with and without torsion are investigated in detail. By carefully analyzing the tangential fluctuations at the boundary, we show explicitly that the physical fluctuations (which at the boundary are combinations of normal and tangential fluctuations) are finite, even though the world-sheet is singular there. The divergent 2-curvature thus seems less dangerous than expected, in these cases. The general formalism can be straightforwardly used also to study the (bosonic part of the) fluctuations around the closed strings, recently considered in connection with the AdS/CFT duality, on AdS_5 \times S^5 and AdS_3 \times S^3 \times T^4.Comment: 19 pages, Late

O(\alpha^2 \ln(m_\mu/m_e)) Corrections to Electron Energy Spectrum in Muon Decay

O(\alpha^2 \ln(m_\mu/m_e)) corrections to electron energy spectrum in muon decay are computed using perturbative fragmentation function approach. The magnitude of these corrections is comparable to anticipated precision of the TWIST experiment at TRIUMF where Michel parameters will be extracted from the measurement of the electron energy spectrum in muon decay.Comment: 8 pages, LaTeX, revtex4.cls, 1 PostScript figur

Spinning Pulsating String Solitons in AdS_5 x S^5

We point out the existence of some simple string solitons in AdS_5 x S^5, which at the same time are spinning in AdS_5 and pulsating in S^5, or vice-versa. This introduces an additional arbitrary constant into the scaling relations between energy and spin or R-charge. The arbitrary constant is not an angular momentum, but can be related to the amplitude of the pulsation. We discuss the solutions in detail and consider the scaling relations. Pulsating multi spin or multi R-charge solutions can also be constructed.Comment: 15 pages, Late

A Note on Exact Solutions and Attractor Mechanism for Non-BPS Black Holes

We obtain two extremal, spherically symmetric, non-BPS black hole solutions to 4D supergravity, one of which carries D2-D6 charges and the other carries D0-D2-D4 charges. For the D2-D6 case, rather than solving the equations of motion directly, we assume the form of the solution and then find that the assumption satisfies the equations of motion and the constraint. Our D2-D6 solution is manifestly dual to the solution presented in 0710.4967. The D0-D2-D4 solution is obtained by performing certain $[SL(2,{\bf Z})]^{3}$ duality transformations on the D0-D4 solution in 0710.4967.Comment: 20 pages, LaTe

Constituent Model of Extremal non-BPS Black Holes

We interpret extremal non-BPS black holes in four dimensions as threshold bound states of four 1/2-BPS constituents. We verify the no-force condition for each of the primitive constituents in the probe approximation. Our computations are for a seed solution with $\bar{D0}-D4$ charges and equal $B$-fields, but symmetries extend the result to any U-dual frame. We make the constituent model for the $D0-D6$ system explicit, and also discuss a duality frame where the constituents are $D3$ branes at angles. We demonstrate stability of the constituent model in the weak coupling description of the constituent D-branes. We discuss the relation between the BPS and non-BPS branches of configuration space.Comment: 29 pages; v2. references adde

A (Running) Bolt for New Reasons

We construct a four-parameter family of smooth, horizonless, stationary solutions of ungauged five-dimensional supergravity by using the four-dimensional Euclidean Schwarzschild metric as a base space and "magnetizing" its bolt. We then generalize this to a five-parameter family based upon the Euclidean Kerr-Taub-Bolt. These "running Bolt" solutions are necessarily non-static. They also have the same charges and mass as a non-extremal black hole with a classically-large horizon area. Moreover, in a certain regime their mass can decrease as their charges increase. The existence of these solutions supports the idea that the singularities of non-extremal black holes are resolved by low-mass modes that correct the singularity of the classical black hole solution on large (horizon-sized) scales.Comment: 25 pages, 3 figures, LaTeX; v2: minor changes, references adde

Emission from the D1D5 CFT

It is believed that the D1D5 brane system is described by an 'orbifold CFT' at a special point in moduli space. We first develop a general formulation relating amplitudes in a d-dimensional CFT to absorption/emission of quanta from flat infinity. We then construct the D1D5 vertex operators for minimally coupled scalars in supergravity, and use these to compute the CFT amplitude for emission from a state carrying a single excitation. Using spectral flow we relate this process to one where we have emission from a highly excited initial state. In each case the radiation rate is found to agree with the radiation found in the gravity dual.Comment: 49 pages, latex, 6 figures; v2: reformatted for JHEP, corrected typos, and added reference

What we don't know about time

String theory has transformed our understanding of geometry, topology and spacetime. Thus, for this special issue of Foundations of Physics commemorating "Forty Years of String Theory", it seems appropriate to step back and ask what we do not understand. As I will discuss, time remains the least understood concept in physical theory. While we have made significant progress in understanding space, our understanding of time has not progressed much beyond the level of a century ago when Einstein introduced the idea of space-time as a combined entity. Thus, I will raise a series of open questions about time, and will review some of the progress that has been made as a roadmap for the future.Comment: 15 pages; Essay for a special issue of Foundations of Physics commemorating "Forty years of string theory