Status and prospects of `bi-large' leptonic mixing

Bi-large patterns for the leptonic mixing matrix are confronted with current neutrino oscillation data. We analyse the status of these patterns and determine, through realistic simulations, the potential of upcoming long-baseline experiment DUNE in testing bi-large \emph{ansatze} and discriminating amongst them.Comment: 14 pages, 7 figures, numerical results refined, some more discussion added. Matches published version of Phys. Let.

Growth rings in tropical trees : role of functional traits, environment, and phylogeny

Acknowledgments Financial support of the Centre National de la Recherche Scientifique (USR 3330), France, and from the Rufford Small Grants Foundation (UK) is acknowledged. We thank the private farmers and coffee plantation companies of Kodagu for providing permissions and logistical support for this project. We are grateful to N. Barathan for assistance with slide preparation and data entry, S. Aravajy for botanical assistance, S. Prasad and G. Orukaimoni for technical inputs, and A. Prathap, S. Shiva, B. Saravana, and P. Shiva for field assistance. The corresponding editor and three anonymous reviewers provided insightful comments that improved the manuscript.Peer reviewedPostprin

Light Element Production in the Circumstellar Matter of Energetic Type Ic Supernovae

We investigate energetic type Ic supernovae as production sites for Li6 and Be in the early stages of the Milky Way. Recent observations have revealed that some very metal-poor stars with [Fe/H]<-2.5 possess unexpectedly high abundances of Li6. Some also exbihit enhanced abundances of Be as well as N. From a theoretical point of view, recent studies of the evolution of metal-poor massive stars show that rotation-induced mixing can enrich the outer H and He layers with C, N, and O (CNO) elements, particularly N, and at the same time cause intense mass loss of these layers. Here we consider energetic supernova explosions occurring after the progeniter star has lost all but a small fraction of the He layer. The fastest portion of the supernova ejecta can interact directly with the circumstellar matter (CSM), both composed of He and CNO, and induce light element production through spallation and He-He fusion reactions. The CSM should be sufficiently thick to energetic particles so that the interactions terminate within its innermost regions. We calculate the resulting Li6/O and Be9/O ratios in the ejecta+CSM material out of which the very metal-poor stars may form. We find that they are consistent with the observed values if the mass of the He layer remaining on the pre-explosion core is 0.01-0.1 solar mass, and the mass fraction of N mixed in the He layer is about 0.01. Further observations of Li6, Be and N at low metallicity should provide critical tests of this production scenario.Comment: 12 pages, 2 figures, revised with referee suggestions, final version accepted in ApJ Letter

Slepton Flavor Nonuniversality, the Muon EDM and its Proposed sensitive Search at Brookhaven

We analyze the electric dipole moment of the electron ($d_e$), of the neutron ($d_n$) and of the muon ($d_{\mu}$) using the cancellation mechanism in the presence of nonuniversalities of the soft breaking parameters. It is shown that the nonuniversalities in the slepton sector produce a strong violation of the scaling relation $d_{\mu}/d_e\simeq m_{\mu}/m_e$ in the cancellation region. An analysis of $d_e, d_n$ and $d_{\mu}$ under the constraints of the current experimental limits on $d_e$ and $d_n$ and under the constraints of the recent Brookhaven result on $g_{\mu}-2$ shows that in the non-scaling region $d_{\mu}$ can be as large as ($10^{-24}-10^{-23}$)ecm and thus within reach of the recently proposed Brookhaven experiment for a sensitive search for $d_{\mu}$ at the level of $10^{-24}$ ecm.Comment: 24 pages, Latex, including 5 figures with additional reference

Testing Supergravity Grand Unification at Future Accelerator and Underground Experiments

The full parameter space of supergravity grand unified theory with $SU(5)$ type $p \rightarrow \bar{\nu} K$ proton decay is analysed using renormalization group induced electroweak symmetry breaking under the restrictions that the universal scalar mass $m_o$ and gluino mass are $\leq 1$ TeV (no extreme fine tuning) and the Higgs triplet mass obeys $M_{H_3}/M_G < 10$. Future proton decay experiments at SuperKamiokande or ICARUS can reach a sensitivity for the $\bar{\nu} K$ mode of $(2-5) \times 10^{33}$ yr allowing a number of predictions concerning the SUSY mass spectrum. Thus either the $p \rightarrow\bar{\nu} K$ decay mode will be seen at these experiments or a chargino of mass $m_{\tilde{W}} < 100$ GeV will exist and hence be observable at LEP2. Further, if $(p \rightarrow \bar{\nu} K) > 1.5 \times 10^{33}$ yr, then either the light Higgs has mass $m_h \leq 95$ GeV or $m_{\tilde{W}} \leq 100$ GeV i.e. either the light Higgs or the light chargino (or both) would be observable at LEP2. Thus, the combination of future accelerator and future underground experiments allow for strong experimental tests of this theory.Comment: 7 figures available upon request, CTP-TAMU-32/93, NUB-TH-3066/93 and SSCL-Preprint-44

Size-dependent electronic-transport mechanism and sign reversal of magnetoresistance in Nd0.5Sr0.5CoO3

A detailed investigation of electronic-transport properties of Nd0.5Sr0.5CoO3 has been carried out as a function of grain size ranging from micrometer order down to an average size of 28 nm. Interestingly, we observe a size induced metal-insulator transition in the lowest grain size sample while the bulk-like sample is metallic in the whole measured temperature regime. An analysis of the temperature dependent resistivity in the metallic regime reveals that the electron-electron interaction is the dominating mechanism while other processes like electron-magnon and electron-phonon scatterings are also likely to be present. The fascinating observation of enhanced low temperature upturn and minimum in resistivity on reduction of grain size is found due to electron-electron interaction (quantum interference effect). This effect is attributed to enhanced disorder on reduction of grain size. Interestingly, we observed a cross over from positive to negative magnetoresistance in the low temperature regime as the grain size is reduced. This observed sign reversal is attributed to enhanced phase separation on decreasing the grain size of the cobaltite

On the Thermodynamic Geometry of Hot QCD

We study the nature of the covariant thermodynamic geometry arising from the free energy of hot QCD. We systematically analyze the underlying equilibrium thermodynamic configurations of the free energy of 2- and 3-flavor hot QCD with or without including thermal fluctuations in the neighborhood of the QCD transition temperature. We show that there exists a well-defined thermodynamic geometric notion for QCD thermodynamics. The geometry thus obtained has no singularity as an intrinsic Riemannian manifold. We further show that there is a close connection of this geometric approach with the existing studies of correlations and quark number susceptibilities in hot QCD.Comment: 15 pages, 12 figures, Keywords: Thermodynamic Geometry, Hot QCD, Quasi-particles, PACS: 12.38.-t; 05.70.Fh; 02.40.Ky; 12.40.E

Hindered magnetic order from mixed dimensionalities in CuP2_2O6_6

We present a combined experimental and theoretical study of the spin-1/2 compound CuP$_2$O$_6$ that features a network of two-dimensional (2D) antiferromagnetic (AFM) square planes, interconnected via one-dimensional (1D) AFM spin chains. Magnetic susceptibility, high-field magnetization, and electron spin resonance (ESR) data, as well as microscopic density-functional band-structure calculations and subsequent quantum Monte-Carlo simulations, show that the coupling $J_{2D}\sim$ 40 K in the layers is an order of magnitude larger than $J_{1D}\sim$ 4 K in the chains. Below $T_N\sim$ 8 K, CuP$_2$O$_6$ develops long-range order (LRO), as evidenced by a weak net moment on the 2D planes induced by anisotropic magnetic interactions of Dzyaloshinsky-Moriya type. A striking feature of this 3D ordering transition is that the 1D moments grow significantly slower than the ones on the 2D layers, which is evidenced by the persistent paramagnetic ESR signal below $T_N$. Compared to typical quasi-2D magnets, the ordering temperature of CuP$_2$O$_6$ $T_N/J_{2D}\sim$ 0.2 is unusually low, showing that weakly coupled spins sandwiched between 2D magnetic units effectively decouple these units and impede the long-range ordering.Comment: 11 pages, 12 figures, 1 table; published version with few additional citations added and misprints fixe

Metal-insulator transitions in tetrahedral semiconductors under lattice change

Although most insulators are expected to undergo insulator to metal transition on lattice compression, tetrahedral semiconductors Si, GaAs and InSb can become metallic on compression as well as by expansion. We focus on the transition by expansion which is rather peculiar; in all cases the direct gap at $\Gamma$ point closes on expansion and thereafter a zero-gap state persists over a wide range of lattice constant. The solids become metallic at an expansion of 13 % to 15 % when an electron fermi surface around L-point and a hole fermi surface at $\Gamma$-point develop. We provide an understanding of this behavior in terms of arguments based on symmetry and simple tight-binding considerations. We also report results on the critical behavior of conductivity in the metal phase and the static dielectric constant in the insulating phase and find common behaviour. We consider the possibility of excitonic phases and distortions which might intervene between insulating and metallic phases.Comment: 12 pages, 8 figure