35,024 research outputs found
Aspects of reduction and transformation of Lagrangian systems with symmetry
This paper contains results on geometric Routh reduction and it is a
continuation of a previous paper where a new class of transformations is
introduced between Lagrangian systems obtained after Routh reduction. In
general, these reduced Lagrangian systems have magnetic force terms and are
singular in the sense that the Lagrangian does not depend on some velocity
components. The main purpose of this paper is to show that the Routh reduction
process itself is entirely captured by the application of such a new
transformation on the initial Lagrangian system with symmetry.Comment: To appear in Journal of Geometric Mechanic
Quark-mass dependence of baryon resonances
We study the quark-mass dependence of J^P = \frac12^- s-wave and J^P =
\frac32^- d-wave baryon resonances. Parameter-free results are obtained in
terms of the leading order chiral Lagrangian. In the 'heavy' SU(3) limit with
m_\pi =m_K \simeq 500 MeV the s-wave resonances turn into bound states forming
two octets plus a singlet representations of the SU(3) group. Similarly the
d-wave resonances turn into bound states forming an octet and a decuplet in
this limit. A contrasted result is obtained in the 'light' SU(3) limit with
m_\pi =m_K \simeq 140 MeV for which no resonances exist.Comment: 8 pages, three figures, talk presented at HYP200
Quantum Phase Transitions in the Interacting Boson Model: Integrability, level repulsion and level crossing
We study the quantum phase transition mechanisms that arise in the
Interacting Boson Model. We show that the second-order nature of the phase
transition from U(5) to O(6) may be attributed to quantum integrability,
whereas all the first-order phase transitions of the model are due to level
repulsion with one singular point of level crossing. We propose a model
Hamiltonian with a true first-order phase transition for finite systems due to
level crossings.Comment: Accepted in PR
Enhancing the Radiative Rate in III-V Semiconductor Plasmonic Core-Shell Nanowire Resonators
We investigate the radiative properties of plasmonic core-shell nanowire resonators and, using boundary element method calculations,
demonstrate enhanced radiative decay rate by up to 3500 times in
nanoscale compound semi-conductor/metal cavities. Calculation of the
local density of optical states enables identification of new types of
modes in cavities with mode volumes on the order of
10^(-4)(λ/n)^3. These modes dramatically enhance the radiative
decay rate and significantly modify the polarization of far-field
emission
Isolated vacua in supersymmetric Yang-Mills theories
An explicit proof of the existence of nontrivial vacua in the pure
supersymmetric Yang-Mills theories with higher orthogonal SO(N), N>=7 or the
G_2 gauge group defined on a 3-torus with periodic boundary conditions is
given. Extra vacuum states are separated by an energy barrier from the
perturbative vacuum A_i=0 and its gauge copies.Comment: 8 pages, no figures, late
Loss of redundant gene expression after polyploidization in plants
Based on chromosomal location data of genes encoding 28 biochemical systems in allohexaploid wheat,Triticum aestivum L. (genomes AABBDD), it is concluded that the proportions of systems controlled by triplicate, duplicate, and single loci are 57%, 25%, and 18% respectively
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