Tagged particle diffusion in one-dimensional gas with Hamiltonian dynamics

We consider a one-dimensional gas of hard point particles in a finite box that are in thermal equilibrium and evolving under Hamiltonian dynamics. Tagged particle correlation functions of the middle particle are studied. For the special case where all particles have the same mass, we obtain analytic results for the velocity auto-correlation function in the short time diffusive regime and the long time approach to the saturation value when finite-size effects become relevant. In the case where the masses are unequal, numerical simulations indicate sub-diffusive behaviour with mean square displacement of the tagged particle growing as t/ln(t) with time t. Also various correlation functions, involving the velocity and position of the tagged particle, show damped oscillations at long times that are absent for the equal mass case.Comment: 13 pages, 5 figures, to be submitted to J. Stat. Phy

Tagged particle diffusion in one-dimensional systems with Hamiltonian dynamics - II

We study various temporal correlation functions of a tagged particle in one-dimensional systems of interacting point particles evolving with Hamiltonian dynamics. Initial conditions of the particles are chosen from the canonical thermal distribution. The correlation functions are studied in finite systems, and their forms examined at short and long times. Various one-dimensional systems are studied. Results of numerical simulations for the Fermi-Pasta-Ulam chain are qualitatively similar to results for the harmonic chain, and agree unexpectedly well with a simple description in terms of linearized equations for damped fluctuating sound waves. Simulation results for the alternate mass hard particle gas reveal that - in contradiction to our earlier results [1] with smaller system sizes - the diffusion constant slowly converges to a constant value, in a manner consistent with mode coupling theories. Our simulations also show that the behaviour of the Lennard-Jones gas depends on its density. At low densities, it behaves like a hard-particle gas, and at high densities like an anharmonic chain. In all the systems studied, the tagged particle was found to show normal diffusion asymptotically, with convergence times depending on the system under study. Finite size effects show up at time scales larger than sound traversal times, their nature being system-specific.Comment: 15 pages, 12 figure

Optical investigation of thermoelectric topological crystalline insulator Pb0.77_{0.77}Sn0.23_{0.23}Se

Pb$_{0.77}$Sn$_{0.23}$Se is a novel alloy of two promising thermoelectric materials PbSe and SnSe that exhibits a temperature dependent band inversion below 300 K. Recent work has shown that this band inversion also coincides with a trivial to nontrivial topological phase transition. To understand how the properties critical to thermoelectric efficiency are affected by the band inversion, we measured the broadband optical response of Pb$_{0.77}$Sn$_{0.23}$Se as a function of temperature. We find clear optical evidence of the band inversion at $160\pm15$ K, and use the extended Drude model to accurately determine a $T^{3/2}$ dependence of the bulk carrier lifetime, associated with electron-acoustic phonon scattering. Due to the high bulk carrier doping level, no discriminating signatures of the topological surface states are found, although their presence cannot be excluded from our data.Comment: 11 pages, 6 figure

Limits on Associated Production of Visibly and Invisibly Decaying Higgs Bosons from Z Decays

Many extensions of the standard electroweak model Higgs sector suggest that the main Higgs decay channel is "invisible", for example, $h \to J J$ where $J$ denotes the majoron, a weakly interacting pseudoscalar Goldstone boson associated to the spontaneous violation of lepton number. In many of these models the Higgs boson may also be produced in association to a massive pseudoscalar boson (HA), in addition to the standard Bjorken mechanism (HZ). We describe a general strategy to determine limits from LEP data on the masses and couplings of such Higgs bosons, using the existing data on acoplanar dijet events as well as data on four and six $b$ jet event topologies. For the sake of illustration, we present constraints that can be obtained for the ALEPH data.Comment: FTUV/94-36, IFIC/94-31 TIFR/TH/94--25, 12 pages + 4 figures (included as ps files at the end

An investigation into the adequacy of existing and alternative property rights regimes to achieve sustainable management of the Sundarbans Mangrove Forest in Bangladesh

This thesis identifies theoretical gaps regarding the adequacy of property rights in achieving sustainable management in the world’s largest Sundarbans Mangrove Forest (SMF) in Bangladesh. This will be achieved through an examination of existing and alternative property rights regimes. Gaps are also pinpointed regarding non-compliance with existing policy in conservation practices and the absence of clear quantitative and qualitative methodical approaches for identifying sustained conservation determinants of the forest. This research aims to fill these gaps by addressing the questions of the adequacy of the existing property rights regime to achieve sustainability. It examines the interaction between property rights and conservation and the necessity for an alternative property rights regime of co-management. It focuses on state property rights regimes within mangrove conservation practices. The subject of this thesis is regarded as one of the oldest mangrove management systems in history, originating in 1875. The thesis adopts a mixed methods research approach involving household survey, content analysis and focus group discussions. Multiple actors, scales and techniques—with a focus on Forest Dependent Communities (FDCs) and conservation practices by the Bangladesh Forest Department (BFD)—are involved in the study. This study considers FDC households as a unit of analysis. Field work was conducted in six villages of the Koyra sub-district and various government offices over a period of four months between November 2010 and February 2011. The field research moves from the household level to the national, division, district, sub-district and international levels. It undertakes a combination of process analysis to establish how mangrove forest conservation is enhanced, the role of FDCs in conservation and why policy fails to advance sustained conservation. Following a review of descriptive statistics, logit model and content analysis, the study finds the state property regime to be inadequate due to the specific and changing socio-cultural, economic, political and ecological contexts of the SMF and its FDCs. Currently, there is a high prevalence of institutionalised corruption and elite dominance. Existing regime embeddedness obstructs FDCs in their attempt to play a role in management and policy-making processes. Without understanding the emergence of the common property regime, FDCs’ positive motivation and collective action cannot be incorporated into sustained conservation policy directives. Along with supply-side property rights interventions in line with Schlager and Ostrom’s (1992) theory, this study justifies some key demand-side interventions to achieve sustainable management. This is expected to overcome state property-related hurdles in achieving sustainability of the SMF. Thereby, it highlights property rights embeddedness to improve FDCs’ socio-economic context through a ‘co-management-alternative livelihood mix’

Genetic variability and character association studies for quality attributing traits in rice (Oryza sativa L.)

Twenty rice genotypes were evaluated for quality attributing traits in the agricultural farm of Uttar Banga Krishi Viswavidyalaya, Pundibari, Cooch Behar, in terai region of West Bengal. The study was conducted in two different environments pre-kharif and kharif seasons during 2017-18. Statistical analysis was performed for the assessment of genotypic coefficient of variation (GCV), phenotypic coefficient variation (PCV), broad sense heritability and genetic advance as percentage of the mean (GAM) for the quality attributing traits viz., kernel length, kernel breadth, l:b ratio of the kernel, kernel length after cooking, kernel breadth after cooking, amylose content, l:b ratio of the cooked kernel and linear elongation ratio. Analysis of variance, GCV and PCV revealed significant variation for different characters under study. Except for kernel length and kernel length after cooking all the characters under study showed high heritability coupled with high GAM. The genotypic correlation study revealed that the l:b ratio of the cooked kernel had a significant positive correlation with linear elongation ratio (LER), while kernel breadth after cooking had a significant negative correlation with LER. Path analysis study revealed that among all the characters, l:b ratio of cooked kernel showed a significant positive correlation with LER and kernel breadth after cooking showed a significant negative correlation with LER. Among the set of 20 genotypes, three were identified as medium slender, seven had medium grain, seven with short medium type and three had short slender grain. Three genotypes namely, Phougak, Phaourin Nakuppi and Chakhao Sempak were found with aroma