11,103 research outputs found
model with Hopf interaction: the quantum theory
The model with Hopf interaction is quantised following the
Batalin-Tyutin (BT) prescription. In this scheme, extra BT fields are
introduced which allow for the existence of only commuting first-class
constraints. Explicit expression for the quantum correction to the expectation
value of the energy density and angular momentum in the physical sector of this
model is derived. The result shows, in the particular operator ordering that we
have chosen to work with, that the quantum effect has a divergent contribution
of in the energy expectation value. But, interestingly
the Hopf term, though topological in nature, can have a finite contribution to energy density in the homotopically nontrivial
topological sector. The angular momentum operator, however, is found to have no
quantum correction, indicating the absence of any fractional spin even at this
quantum level. Finally, the extended Lagrangian incorporating the BT auxiliary
fields is computed in the conventional framework of BRST formalism exploiting
Faddeev-Popov technique of path integral method.Comment: LaTeX, 28 pages, no figures, typos corrected, journal ref. give
Determinant Quantum Monte Carlo Study of the Screening of the One Body Potential near a Metal-Insulator Transition
In this paper we present a determinant quantum monte carlo study of the two
dimensional Hubbard model with random site disorder. We show that, as in the
case of bond disorder, the system undergoes a transition from an Anderson
insulating phase to a metallic phase as the onsite repulsion U is increased
beyond a critical value U_c. However, there appears to be no sharp signal of
this metal-insulator transition in the screened site energies. We observe that,
while the system remains metallic for interaction values upto twice U_c, the
conductivity is maximal in the metallic phase just beyond U_c, and decreases
for larger correlation.Comment: 6 pages, 10 eps figures, Revtex
PGPR in Managing Root Rot Disease and Enhancing Growth in Mandarin (Citrus reticulata Blanco.) Seedlings
Decline in general plant-health and fruit production in mandarin influenced by abiotic and biotic factors is a major threat to cultivars grown in Darjeeling and Sikkim hills. Fusarium root rot, caused by F. oxysporum, is one of the most serious diseases afflicted during early plant growth stage in Citrus. To address this, seven PGPR isolates - Pseudomonas poae (RMK03), Bacillus stratosphericus (RHS/CL-01), Ochrobactrum anthropi, Paenibacillus lentimorbus, Bacillus pumilus, Bacillus megaterium and Bacillus amyloliquefaciens were isolated from the rhizosphere of Citrus reticulata, C. limonia and Camellia sinensis, and used for evaluating their effect on growth of mandarin seedlings. Pseudomonas poae showed in vitro antagonism to Fusarium oxysporum. Better growth enhancement was noticed with P. poae, B. stratosphericus, O. anthropi and B. pumilus. Enhanced activity of chlorophyll, total protein, phenol, four major defense enzymeschitinase, β-1, 3-glucanase, peroxidase and phenyalanine ammonia lyase was observed upon application of PGPR. P. poae also suppressed root rot caused by Fusarium oxysporum. Use of PGPR, which promote growth besides reducing disease severity to some extent, may lead to use of eco-friendly approaches for controlling plant diseases
Wigner Oscillators, Twisted Hopf Algebras and Second Quantization
By correctly identifying the role of central extension in the centrally
extended Heisenberg algebra h, we show that it is indeed possible to construct
a Hopf algebraic structure on the corresponding enveloping algebra U(h) and
eventually deform it through Drinfeld twist. This Hopf algebraic structure and
its deformed version U^F(h) are shown to be induced from a more fundamental
Hopf algebra obtained from the Schroedinger field/oscillator algebra and its
deformed version, provided that the fields/oscillators are regarded as
odd-elements of the super-algebra osp(1|2n). We also discuss the possible
implications in the context of quantum statistics.Comment: 23 page
Unveiling Su Aurigae in the near Infrared: New high spatial resolution results using Adaptive Optics
We present here new results on circumstellar nebulosity around SU Aurigae, a
T-Tauri star of about 2 solar mass and 5 Myrs old at 152 pc in the J, H and K
bands using high resolution adaptive optics imaging (0\farcs30) with the Penn
state IR Imaging Spectrograph (PIRIS) at the 100 inch Mt. Wilson telescope.
A comparison with HST STIS optical (0.2 to 1.1 micron) images shows that the
orientation of the circumstellar nebulosity in the near-IR extends from PAs 210
to 270 degrees in H and K bands and up to 300 degrees in the J band. We call
the circumstellar nebulosity seen between 210 to 270 degrees as 'IR
nebulosity'. We find that the IR nebulosity (which extends up to 3.5 arcsecs in
J band and 2.5 arcsecs in the K band) is due to scattered light from the
central star. The IR nebulosity is either a cavity formed by the stellar
outflows or part of the circumstellar disk. We present a schematic
3-dimensional geometrical model of the disk and jet of SU Aur based on STIS and
our near-IR observations. According to this model the IR nebulosity is a part
of the circumstellar disk seen at high inclination angles. The extension of the
IR nebulosity is consistent with estimates of the disk diameter of 50 to 400 AU
in radius, from earlier mm, K band interferometric observations and SED
fittings.Comment: Accepted for publications in the Astronomical Journal, to appear in
the May issue of the Journa
Why Do Granular Materials Stiffen with Shear Rate? : Test of Novel Stress-Based Statistics
Peer reviewedPublisher PD
Spectrum of the non-commutative spherical well
We give precise meaning to piecewise constant potentials in non-commutative
quantum mechanics. In particular we discuss the infinite and finite
non-commutative spherical well in two dimensions. Using this, bound-states and
scattering can be discussed unambiguously. Here we focus on the infinite well
and solve for the eigenvalues and eigenfunctions. We find that time reversal
symmetry is broken by the non-commutativity. We show that in the commutative
and thermodynamic limits the eigenstates and eigenfunctions of the commutative
spherical well are recovered and time reversal symmetry is restored
Spin Polarizations at and about the Lowest Filled Landau Level
The spin polarization versus temperature at or near a fully filled lowest
Landau level is explored for finite-size systems in a periodic rectangular
geometry. Our results at which also include the finite-thickness
correction are in good agreement with the experimental results. We also find
that the interacting electron system results are in complete agreement with the
results of the sigma model, i.e., skyrmions on a torus have a topological
charge of and the Q=1 solution is like a single spin-flip excitation.
Our results therefore provide direct evidence for the skyrmionic nature of the
excitations at this filling factor.Comment: 4 pages, REVTEX, and 4 .ps files, To be published in Europhysics
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