Formation of caustics in Dirac-Born-Infeld type scalar field systems

We investigate the formation of caustics in Dirac-Born-Infeld type scalar field systems for generic classes of potentials, viz., massive rolling scalar with potential, $V(\phi)=V_0e^{\pm \frac{1}{2} M^2 \phi^2}$ and inverse power-law potentials with $V(\phi)=V_0/\phi^n,~0<n<2$. We find that in the case of\texttt{} exponentially decreasing rolling massive scalar field potential, there are multi-valued regions and regions of likely to be caustics in the field configuration. However there are no caustics in the case of exponentially increasing potential. We show that the formation of caustics is inevitable for the inverse power-law potentials under consideration in Minkowski space time whereas caustics do not form in this case in the FRW universe.Comment: 16 pages, 14 figures, major revision, conclusions strengthen, to appear in PR

Global oscillation analysis of solar neutrino data with helioseismically constrained fluxes

A seismic model for the Sun calculated using the accurate helioseismic data predicts a lower $^{8}{B}$ neutrino flux as compared to the standard solar model (SSM). However, there persists a discrepancy between the predicted and measured neutrino fluxes and it seems necessary to invoke neutrino oscillations to explain the measurements. In this work, we have performed a global, unified oscillation analysis of the latest solar neutrino data (including the results of SNO charged current rate) using the seismic model fluxes as theoretical predictions. We determine the best-fit values of the neutrino oscillation parameters and the $\chi^2_{\mathrm min}$ for both $\nu_e-\nu_{\mathrm active}$ and $\nu_e -\nu_{\mathrm sterile}$ cases and present the allowed parameter regions in the $\Delta m^2 - \tan^2 \theta$ plane for $\nu_e-\nu_{\mathrm active}$ transition. The results are compared with those obtained using the latest SSM by Bahcall and his collaborators.Comment: Version to appear in Phys. Rev.

Laser phase modulation approaches towards ensemble quantum computing

Selective control of decoherence is demonstrated for a multilevel system by generalizing the instantaneous phase of any chirped pulse as individual terms of a Taylor series expansion. In the case of a simple two-level system, all odd terms in the series lead to population inversion while the even terms lead to self-induced transparency. These results also hold for multiphoton transitions that do not have any lower-order photon resonance or any intermediate virtual state dynamics within the laser pulse-width. Such results form the basis of a robustly implementable CNOT gate.Comment: 10 pages, 4 figures, PRL (accepted

Perspective of beneficial microbes in agriculture under changing climatic scenario: a review

Agriculture is a complex network of interactions of plants with microorganisms. There is a growing demand for ecologically compatible environment friendly technique in agriculture that might be able to provide adequate supply of nutrients for the increasing human populations through improvement of the quality and quantity of agricultural products. Under the changing climatic scenario of global fluxes of the key biogenic greenhouse gases (CO2, methane and nitrous oxide), and some other environmental problems, the application of beneficial microorganisms in agriculture would serve as an important alternative gateway to some of the traditional agricultural techniques. Microorganisms of agricultural importance represent key ecological strategy for integrated management practices like nutrient management, disease and pest management in order to reduce the use of chemicals in agriculture as well to improve cultivar performance. The present review is intended to focus on the emergence of agriculturally important microorganisms (AIMs) to develop an ideal agricultural system through efficient utilization of nutrients and recycling of energy and thereby to preserve the natural ecosystem resources under climate change. The progress to date in using the beneficial microflora in a variety of applications related to agriculture along with key mechanism of action is also discussed in this review

Earth Matter Effects at Very Long Baselines and the Neutrino Mass Hierarchy

We study matter effects which arise in the muon neutrino oscillation and survival probabilities relevant to atmospheric neutrino and very long baseline beam experiments. The inter-relations between the three probabilities P_{\mu e}, P_{\mu \tau} and P_{\mu \mu} are examined. It is shown that large and observable sensitivity to the neutrino mass hierarchy can be present in P_{\mu \mu} and P_{\mu \tau}. We emphasize that at baselines of > 7000 Km, matter effects in P_{\mu \tau} can be large under certain conditions. The muon survival rates in experiments with very long baselines thus depend on matter effects in both P_{\mu \tau} and P_{\mu e}. We indicate where these effects are sensitive to \theta_{13}, and identify ranges of E and L where the event rates increase with decreasing \theta_{13}, providing a handle to probe small \theta_{13}. The effect of parameter degeneracies in the three probabilities at these baselines and energies is studied in detail. Realistic event rate calculations are performed for a charge discriminating 100 kT iron calorimeter which demonstrate the possibility of realising the goal of determining the neutrino mass hierarchy using atmospheric neutrinos. It is shown that a careful selection of energy and baseline ranges is necessary in order to obtain a statistically significant signal, and that the effects are largest in bins where matter effects in both P_{\mu e} and P_{\mu \tau} combine constructively. Under these conditions, upto a 4\sigma signal for matter effects is possible (for \Delta_{31}>0) within a timescale appreciably shorter than the one anticipated for neutrino factories.Comment: 40 pages, 27 figures, version to match the published versio

Dissipation, topology, and quantum phase transition in a one-dimensional Joesphson junction array

We study the phase diagram and quantum critical properties of a resistively shunted Josephson junction array in one dimension from a strong coupling analysis. After mapping the dissipative quantum phase model to an effective sine-Gordon model we study the renormalization group flow and the phase diagram. We try to bridge the phase diagrams obtained from the weak and the strong coupling renormalization group calculations to extract a more comprehensive picture of the complete phase diagram. The relevance of our theory to experiments in nanowires is discussed.Comment: 13 pages, 3 figures, A few typos are correcte

The tetralogy of Birkhoff theorems

We classify the existent Birkhoff-type theorems into four classes: First, in field theory, the theorem states the absence of helicity 0- and spin 0-parts of the gravitational field. Second, in relativistic astrophysics, it is the statement that the gravitational far-field of a spherically symmetric star carries, apart from its mass, no information about the star; therefore, a radially oscillating star has a static gravitational far-field. Third, in mathematical physics, Birkhoff's theorem reads: up to singular exceptions of measure zero, the spherically symmetric solutions of Einstein's vacuum field equation with Lambda = 0 can be expressed by the Schwarzschild metric; for Lambda unequal 0, it is the Schwarzschild-de Sitter metric instead. Fourth, in differential geometry, any statement of the type: every member of a family of pseudo-Riemannian space-times has more isometries than expected from the original metric ansatz, carries the name Birkhoff-type theorem. Within the fourth of these classes we present some new results with further values of dimension and signature of the related spaces; including them are some counterexamples: families of space-times where no Birkhoff-type theorem is valid. These counterexamples further confirm the conjecture, that the Birkhoff-type theorems have their origin in the property, that the two eigenvalues of the Ricci tensor of two-dimensional pseudo-Riemannian spaces always coincide, a property not having an analogy in higher dimensions. Hence, Birkhoff-type theorems exist only for those physical situations which are reducible to two dimensions.Comment: 26 pages, updated references, minor text changes, accepted by Gen. Relat. Gra

Nucleosynthesis of Zinc and Iron-Peak Elements in Pop III Type II Supernovae : Comparison with abundances of Very Metal-Poor Halo Stars

We calculate nucleosynthesis in core-collapse explosions of massive Pop III stars, and compare the results with abundances of metal-poor halo stars to constrain the parameters of Pop III supernovae. We focus on iron-peak elements and, in particular, we try to reproduce the large [Zn/Fe] observed in extremely metal-poor stars. The interesting trends of the observed ratios [Zn, Co, Mn, Cr, V/Fe] can be related to the variation of the relative mass of the complete and incomplete Si-burning regions in supernova ejecta. We find that [Zn/Fe] is larger for deeper mass-cuts, smaller neutron excess, and larger explosion energies. The large [Zn/Fe] and [O/Fe] observed in the very metal-poor halo stars suggest deep mixing of complete Si-burning material and a significant amount of fall-back in Type II supernovae. Furthermore, large explosion energies (E_51 >~ 2 for M ~ 13 Msun and E_51 >~ 20 for M >~ 20 Msun) are required to reproduce [Zn/Fe] ~ 0.5. The observed trends of the abundance ratios among the iron-peak elements are better explained with this high energy (``Hypernova'') models rather than the simple ``deep'' mass-cut effect, because the overabundance of Ni can be avoided in the hypernova models. We also present the yields of pair-instability supernova explosions of M = 130 - 300 Msun stars, and discuss that the abundance features of very metal-poor stars cannot be explained by pair-instability supernovae.Comment: 32 pages, 19 figures, 18 tables. To appear in the Astrophysical Journal 2002, 565. Table 18 of yields of Pop III Pair-Instability Supernovae is replaced with a new on

Stability prediction of residual soil and rock slope using artificial neural network

A sudden downward movement of the geomaterial, either composed of soil, rock, or a mixture of both, along the mountain slopes due to various natural or anthropogenic factors is known as a landslide. The Himalayan Mountain slopes are either made up of residual soil or rocks. Residual soil is formed from weathering of the bedrock and mainly occurs in gentle-to-moderate slope inclinations. In contrast, steep slopes are mostly devoid of soil cover and are primarily rocky. A stability prediction system that can analyse the slope under both the condition of the soil or rock surface is missing. In this study, artificial neural network technology has been utilised to predict the stability of jointed rock and residual soil slope of the Himalayan region. The database for the artificial neural network was obtained from numerical simulation of several residual soils and rock slope models. Nonlinear equations have been formulated by coding the artificial neural network algorithm. An android application has also been developed to predict the stability of residual soil and rock slope instantly. It was observed that the developed android app provides promising results in predicting the factor of safety and stability state of the slopes. © 2022 Mahesh Paliwal et al. This is an open access article distributed under the Creative Commons Attribution License