The Best-or-Worst and the Postdoc problems

We consider two variants of the secretary problem, the\emph{ Best-or-Worst} and the \emph{Postdoc} problems, which are closely related. First, we prove that both variants, in their standard form with binary payoff 1 or 0, share the same optimal stopping rule. We also consider additional cost/perquisites depending on the number of interviewed candidates. In these situations the optimal strategies are very different. Finally, we also focus on the Best-or-Worst variant with different payments depending on whether the selected candidate is the best or the worst

What if Newton's Gravitational Constant was negative?

In this work, we seek a cosmological mechanism that may define the sign of the effective gravitational coupling constant, {\em G}. To this end, we consider general scalar-tensor gravity theories as they provide the field theory natural framework for the variation of the gravitational coupling. We find that models with a quadratic potential naturally stabilize the value of {\em G} into the positive branch of the evolution and further, that de Sitter inflation and a relaxation to General Relativity is easily attained.Comment: 16 pages, 16 figure

Theoretical Study of Ultrafast Electron Dynamics in Amino Acids

Prompt ioiuzatiou of large biological molecules may mince ultra fast charge migration along the molecular skeleton, preceding any unclear rearrangement[1, 2]. This phenomenon lots been recently observed in the amino acid phenylalanine [3] in a two-color pump probe experiment, where the production of ionic fragments Was measured as a function of the time delay between the two pulses and charge fluctuations manifested as sub-4.5 fs oscillations in the quantum yield of a spcific doubly charged fragment. We present our latcst results in glycine, and compare with previous findings in pheitylalanine [3]. We seek to perform a systematic study including larger aminoncids such as tryptophan