462,636 research outputs found
Multi-Photon Interference and Temporal Distinguishability of Photons
A number of recent interference experiments involving multiple photons are
reviewed. These experiments include generalized photon bunching effects,
generalized Hong-Ou-Mandel interference effects and multi-photon interferometry
for demonstrations of multi-photon de Broglie wavelength. The multi-photon
states used in these experiments are from two pairs of photons in parametric
down-conversion. We find that the size of the interference effect in these
experiments, characterized by the visibility of interference pattern, is
governed by the degree of distinguishability among different pairs of photons.
Based on this discovery, we generalize the concept of multi-photon temporal
distinguishability and relate it to a number of multi-photon interference
effects. Finally, we make an attempt to interpret the coherence theory by the
multi-photon interference via the concept of temporal distinguishability of
photons.Comment: fixed figures 4,5,
Why T_c is too high when antiferromagnetism is underestimated? --- An understanding based on the phase string effect
It is natural for a Mott antiferromagnetism in RVB description to become a
superconductor in doped metallic regime. But the issue of superconducting
transition temperature is highly nontrivial, as the AF fluctuations in the form
of RVB pair-breaking are crucial in determining the phase coherence of the
superconductivity. Underestimated AF fluctuations in a fermionic RVB state are
the essential reason causing an overestimate of T_c in the same system. We
point out that by starting with a {\it bosonic} RVB description where both the
long-range and short-range AF correlations can be accurately described, the AF
fluctuations can effectively reduce T_c to a reasonable value through the phase
string effect, by controlling the phase coherence of the superconducting order
parameter.Comment: Latex; two figure
Diverse Supernova Sources for the r-Process and Abundances in Metal-Poor Stars
The dispersion and mean trends of r-process abundances in metal-poor stars
are discussed based on a model of diverse supernova sources for the r-process.
This model is unique in that its key parameters are inferred from solar system
data independent of stellar observations at low metallicities. It is shown that
this model provides a good explanation for the observed dispersion and mean
trend of Eu abundances over -3 < [Fe/H] < -1. It is also shown that this model
provides a means to discuss r-abundances in general. For example, the Ag
abundance in any metal-poor star with observed Eu and Fe abundances can be
calculated from the model. This approach is demonstrated with success for two
stars and can be further tested by future Ag data. The dispersion and mean
trend of Ag abundances in metal-poor stars are also calculated for comparison
with future observations.Comment: 4 pages, 2 figures, to appear in ApJL (submitted February 1, 2001
The tensor structure on the representation category of the triplet algebra
We study the braided monoidal structure that the fusion product induces on
the abelian category -mod, the category of representations of
the triplet -algebra . The -algebras are a
family of vertex operator algebras that form the simplest known examples of
symmetry algebras of logarithmic conformal field theories. We formalise the
methods for computing fusion products, developed by Nahm, Gaberdiel and Kausch,
that are widely used in the physics literature and illustrate a systematic
approach to calculating fusion products in non-semi-simple representation
categories. We apply these methods to the braided monoidal structure of
-mod, previously constructed by Huang, Lepowsky and Zhang, to
prove that this braided monoidal structure is rigid. The rigidity of
-mod allows us to prove explicit formulae for the fusion product
on the set of all simple and all projective -modules, which were
first conjectured by Fuchs, Hwang, Semikhatov and Tipunin; and Gaberdiel and
Runkel.Comment: 58 pages; edit: added references and revisions according to referee
reports. Version to appear on J. Phys.
- …