Multiferroic coupling in nanoscale BiFeO3

Using the results of x-ray and neutron diffraction experiments, we show that the ferroelectric polarization, in ~22 nm particles of BiFeO3, exhibits a jump by ~30% around the magnetic transition point T_N (~635 K) and a suppression by ~7% under 5T magnetic field at room temperature (<<T_N). These results confirm presence of strong multiferroic coupling even in nanoscale BiFeO3 and thus could prove to be quite useful for applications based on nanosized devices of BiFeO3.Comment: 4 pages including 4 figures and supplementary data; accepted for publication in Appl. Phys. Let

Large U_{e3} and Tri-bimaximal Mixing

We investigate in a model-independent way to what extent one can perturb tri-bimaximal mixing in order to generate a sizable value of |U_{e3}|, while at the same time keeping solar neutrino mixing near its measured value, which is close to sin^2 theta_{12} = 1/3. Three straightforward breaking mechanisms to generate |U_{e3}| of about 0.1 are considered. For charged lepton corrections, the suppression of a sizable contribution to sin^2 theta_{12} can be achieved if CP violation in neutrino oscillations is almost maximal. Generation of the indicated value of |U_{e3}| of about 0.1 through renormalization group corrections requires the neutrinos to be quasi-degenerate in mass. The consistency with the allowed range of sin^2 theta_{12} together with large running of |U_{e3}| forces one of the Majorana phases to be close to pi. This implies large cancellations in the effective Majorana mass governing neutrino-less double beta, constraining it to lie near its minimum allowed value of m_0 cos 2 theta_{12}, where m_0 is greater than about 0.1 eV. Finally, explicit breaking of the neutrino mass matrix in the inverted hierarchical and quasi-degenerate neutrino mass spectrum cases is similarly correlated with the effective Majorana mass, although to a lesser extent. The implied values for the atmospheric neutrino mixing angle theta_{23} are given in all cases.Comment: 20 pages, 9 figure

Renormalization group evolution of neutrino mixing parameters near θ13=0\theta_{13} = 0 and models with vanishing θ13\theta_{13} at the high scale

Renormalization group (RG) evolution of the neutrino mass matrix may take the value of the mixing angle $\theta_{13}$ very close to zero, or make it vanish. On the other hand, starting from $\theta_{13}=0$ at the high scale it may be possible to generate a non-zero $\theta_{13}$ radiatively. In the most general scenario with non-vanishing CP violating Dirac and Majorana phases, we explore the evolution in the vicinity of $\theta_{13}=0$, in terms of its structure in the complex ${\cal U}_{e3}$ plane. This allows us to explain the apparent singularity in the evolution of the Dirac CP phase $\delta$ at $\theta_{13}=0$. We also introduce a formalism for calculating the RG evolution of neutrino parameters that uses the Jarlskog invariant and naturally avoids this singular behaviour. We find that the parameters need to be extremely fine-tuned in order to get exactly vanishing $\theta_{13}$ during evolution. For the class of neutrino mass models with $\theta_{13}=0$ at the high scale, we calculate the extent to which RG evolution can generate a nonzero $\theta_{13}$, when the low energy effective theory is the standard model or its minimal supersymmetric extension. We find correlated constraints on $\theta_{13}$, the lightest neutrino mass $m_0$, the effective Majorana mass $m_{ee}$ measured in the neutrinoless double beta decay, and the supersymmetric parameter $\tan\beta$.Comment: 24 pages, 6 figures, revtex

Solar Model Parameters and Direct Measurements of Solar Neutrino Fluxes

We explore a novel possibility of determining the solar model parameters, which serve as input in the calculations of the solar neutrino fluxes, by exploiting the data from direct measurements of the fluxes. More specifically, we use the rather precise value of the $^8B$ neutrino flux, $\phi_B$ obtained from the global analysis of the solar neutrino and KamLAND data, to derive constraints on each of the solar model parameters on which $\phi_B$ depends. We also use more precise values of $^7Be$ and $pp$ fluxes as can be obtained from future prospective data and discuss whether such measurements can help in reducing the uncertainties of one or more input parameters of the Standard Solar Model.Comment: 25 pages, 3 figure

Understanding Genomic Evolution of Olfactory Receptors through Fractal and Mathematical Morphology

Fractals and Mathematical Morphology are immensely used to study many problems in different branches of science and technology including the domain of Biology. There are many more unrevealed facts and figures of genes and genome in Computational Biology. In this paper, our objective is to explore how the evolutionary network is associated among Human, Chimpanzee and Mouse with regards to their genomic information. We are about to explore their genomic evolution through the quantitative measures of fractals and morphology. We have considered olfactory receptors for our case study. These olfactory receptors do function in different species with subtle differences in the structures of DNA sequences. Those subtle differences can be exposed through intricate details of Fractals and Mathematical Morphology

Constraining Mass Spectra with Sterile Neutrinos from Neutrinoless Double Beta Decay, Tritium Beta Decay and Cosmology

We analyze the constraints on neutrino mass spectra with extra sterile neutrinos as implied by the LSND experiment. The various mass related observables in neutrinoless double beta decay, tritium beta decay and cosmology are discussed. Both neutrino oscillation results as well as recent cosmological neutrino mass bounds are taken into account. We find that some of the allowed mass patterns are severely restricted by the current constraints, in particular by the cosmological constraints on the total sum of neutrino masses and by the non-maximality of the solar neutrino mixing angle. Furthermore, we estimate the form of the four neutrino mass matrices and also comment on the situation in scenarios with two additional sterile neutrinos.Comment: 40 pages, 9 figures. Minor changes, matches version in PR

A common spatial mode for intra-seasonal and inter-annual variation and predictability of the Indian summer monsoon

How and to what extent the intra-seasonal oscillations (ISOs) of the Indian summer monsoon influence the seasonal mean and its inter-annual variability is investigated using long records of daily circulation data (1956-1997) and outgoing long wave radiation (OLR) data (1974-1997). The underlying spatial structure of a typical ISO cycle that is invariant from event to event and year to year is brought out. It is shown that the intra-seasonal and interannual variations are governed by a common mode of spatial variability. A higher frequency of occurrence of 'active' ('break') conditions within a monsoon season, therefore, could result in a 'strong' ('weak') summer monsoon. Two-dimensional probability density function estimates of the ISOs show that 'strong' ('weak') monsoon years are indeed associated with higher probability of occurrence of 'active' ('break') conditions. For the first time, these results show that the frequency of chaotic ISO regimes determine the seasonal mean monsoon, thereby setting a limit on monsoon predictability