85,169 research outputs found
Monte Carlo Studies of the Fundamental Limits of the Intrinsic Hyperpolarizability
The off-resonant hyperpolarizability is calculated using the dipole-free
sum-over-stats expression from a randomly chosen set of energies and transition
dipole moments that are forced to be consistent with the sum rules. The process
is repeated so that the distribution of hyperpolarizabilities can be
determined. We find this distribution to be a cycloid-like function. In
contrast to variational techniques that when applied to the potential energy
function yield an intrinsic hyperpolarizability less than 0.71, our Monte Carlo
method yields values that approach unity. While many transition dipole moments
are large when the calculated hyperpolarizability is near the fundamental
limit, only two excited states dominate the hyperpolarizability - consistent
with the three-level ansatz.Comment: 7 pages, 5 figure
Gravity from a Modified Commutator
We show that a suitably chosen position-momentum commutator can elegantly
describe many features of gravity, including the IR/UV correspondence and
dimensional reduction (`holography'). Using the most simplistic example based
on dimensional analysis of black holes, we construct a commutator which
qualitatively exhibits these novel properties of gravity. Dimensional reduction
occurs because the quanta size grow quickly with momenta, and thus cannot be
"packed together" as densely as naively expected. We conjecture that a more
precise form of this commutator should be able to quantitatively reproduce all
of these features.Comment: 8 pages; Honorable Mention in the 2005 Gravity Research Foundation
Essay Competition; v2: acknowledgments adde
Color superconductivity and the strange quark
At ultra-high density, matter is expected to form a degenerate Fermi gas of
quarks in which there is a condensate of Cooper pairs of quarks near the Fermi
surface: color superconductivity. In these proceedings I review some of the
underlying physics, and discuss outstanding questions about the phase structure
of ultra-dense quark matter.Comment: 11 pages, proceedings of QCD@Work 2005 and Johns Hopkins Workshop
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