CP1CP^{1} model with Hopf interaction: the quantum theory

The $CP^1$ 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 ${\cal O} (\hbar^2)$ in the energy expectation value. But, interestingly the Hopf term, though topological in nature, can have a finite ${\cal O} (\hbar)$ 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 $\nu=1$ 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 $Q \ge 2$ 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 Letter