8,068 research outputs found
Negative forms and path space forms
We present an account of negative differential forms within a natural
algebraic framework of differential graded algebras, and explain their
relationship with forms on path spaces.Comment: 12 pp.; the Introduction has been rewritten and mention of cohomology
dropped in Proposition 3.2; material slightly reorganize
Loop Corrections in the Spectrum of 2D Hawking Radiation
We determine the one-loop and the two-loop back-reaction corrections in the
spectrum of the Hawking radiation for the CGHS model of 2d dilaton gravity by
evaluating the Bogoliubov coefficients for a massless scalar field propagating
on the corresponding backgrounds. Since the back-reaction can induce a small
shift in the position of the classical horizon, we find that a positive shift
leads to a non-Planckian late-time spectrum, while a null or a negative shift
leads to a Planckian late-time spectrum in the leading-order stationary-point
approximation. In the one-loop case there are no corrections to the classical
Hawking temperature, while in the two-loop case the temperature is three times
greater than the classical value. We argue that these results are consistent
with the behaviour of the Hawking flux obtained from the operator quantization
only for the times which are not too late, in accordance with the limits of
validity of the semiclassical approximation.Comment: 20 pages, latex, no figure
Impact of Social Networks on the Spread of Disease
https://scholar.dsu.edu/research-symposium/1023/thumbnail.jp
On the homology of the Harmonic Archipelago
We calculate the singular homology and \v{C}ech cohomology groups of the
Harmonic archipelago. As a corollary, we prove that this space is not homotopy
equivalent to the Griffiths space. This is interesting in view of Eda's proof
that the first singular homology groups of these spaces are isomorphic
Normal Mode Determination of Perovskite Crystal Structures with Octahedral Rotations: Theory and Applications
Nuclear site analysis methods are used to enumerate the normal modes of
perovskite polymorphs with octahedral rotations. We provide the modes
of the fourteen subgroups of the cubic aristotype describing the Glazer
octahedral tilt patterns, which are obtained from rotations of the
octahedra with different sense and amplitude about high symmetry axes. We
tabulate all normal modes of each tilt system and specify the contribution of
each atomic species to the mode displacement pattern, elucidating the physical
meaning of the symmetry unique modes. We have systematically generated 705
schematic atomic displacement patterns for the normal modes of all 15 (14
rotated + 1 unrotated) Glazer tilt systems. We show through some illustrative
examples how to use these tables to identify the octahedral rotations,
symmetric breathing, and first-order Jahn-Teller anti-symmetric breathing
distortions of the octahedra, and the associated Raman selection
rules. We anticipate that these tables and schematics will be useful in
understanding the lattice dynamics of bulk perovskites and would serve as
reference point in elucidating the atomic origin of a wide range of physical
properties in synthetic perovskite thin films and superlattices.Comment: 17 pages, 3 figures, 17 tables. Supporting information accessed
through link specified within manuscrip
Scyllarid Lobster Biology and Ecology
The family Scyllaridae is the most speciose and diverse of all families of marine lobsters. Slipper lobsters are found in both tropical and temperate habitats with hard or soft substrates and at different depths, and exhibit a wide array of morphological, anatomical, and physiological adaptations. Among the 20 genera and at least 89 species constituting 4 subfamilies, only some members of 4 genera, Thenus (Theninae), Scyllarides (Arctidinae), Ibacus and Parribacus (Ibacinae), form significant fisheries because of their large size. While scientific information on these lobsters has increased considerably in recent decades, it is still limited compared with commercially valuable spiny and clawed lobsters, and is confined to a few key species. The present chapter presents the current available knowledge on the biology of scyllarids and attempts to point out where questions remain to help focus further studies in this important group
- …