arXiv subjects
Publications and source records attributed to Neal Dalal.
We investigate the so-called magnification relations of gravitational lensing models. We show that multidimensional residue integrals provide a simple explanation for the existence of these relations, and an effective method of computation. We illustrate the method with several examples, thereby deriving new magnification relations for galaxy lens models and microlensing (point mass lensing).
In light of recent evidence suggesting a nonzero present-day cosmological constant, Adams, Mbonye, & Laughlin (1999) have considered the evolution of black holes in the presence of vacuum energy. Using the assumption that Lambda remains constant with time, and a conjecture based on a paper by Mallett (1986), they reach the remarkable conclusion that black holes with current mass greater than about 2*10^(-9) Msun will not Hawking evaporate in the distant future, but will instead absorb vacuum energy and grow to roughly the de Sitter horizon size. In this letter we reexamine black hole evaporation in the presence of vacuum energy, and find instead that all known black holes will eventually evaporate.
We introduce a new method of searching for and characterizing extra-solar planets. We show that by monitoring the center-of-light motion of microlensing alerts using the next generation of high precision astrometric instruments the probability of detecting a planet orbiting the lens is high. We show that adding astrometric information to the photometric microlensing lightcurve greatly helps in determining the planetary mass and semi-major axis. We introduce astrometric maps as a new way for calculating astrometric motion and planet detection probabilities. Finite source effects are important for low mass planets, but even Earth mass planets can give detectable signals.