Higher-order topological insulators in amorphous solids

We identify the possibility of realizing higher order topological (HOT) phases in noncrystalline or amorphous materials. Starting from two- and three-dimensional crystalline HOT insulators, accommodating topological corner states, we gradually enhance structural randomness in the system. Within a parameter regime, as long as amorphousness is confined by an outer crystalline boundary, the system continues to host corner states, yielding amorphous HOT insulators. However, as structural disorder percolates to the edges, corner states start to dissolve into amorphous bulk, and ultimately the system becomes a trivial insulator when amorphousness plagues the entire system. These outcomes are further substantiated by computing the quadrupolar (octupolar) moment in two (three) dimensions. Therefore, HOT phases can be realized in amorphous solids, when wrapped by a thin (lithographically grown, for example) crystalline layer. Our findings suggest that crystalline topological phases can be realized even in the absence of local crystalline symmetry

Statistics-tuned phases of pseudofermions in one dimension

We show that a quadratic system of pseudofermions, with tunable fractionalised statistics, can host a rich phase diagram on a one dimensional chain with nearest and next nearest neighbor hopping. Using a combination of numerical and analytical techniques, we show that that by varying the statistical angle and the ratio of the hopping, the system stabilizes two Tomonaga-Luttinger liquids (TLL) with central charges c = 1 and 2 respectively along with the inversion symmetry broken bond ordered (BO) insulating phase. Interestingly, the two quantum phase transitions in the system - (1) between the two TLLs, and, (2) the c = 1 TLL and BO phase can be engendered by solely tuning the statistics of the pseudofermions. Our analysis shows that both these transition are continuous and novel with the former lacking a local order-parameter based description and the latter of Berezinskii-Kosterlitz-Thouless type. These phases and phase transitions can be of direct experimental relevance in context of recent studies of fermionic cold atoms.Comment: 6+12 pages, 4+14 figure

Level Density of a Bose Gas and Extreme Value Statistics

We establish a connection between the level density of a gas of non-interacting bosons and the theory of extreme value statistics. Depending on the exponent that characterizes the growth of the underlying single-particle spectrum, we show that at a given excitation energy the limiting distribution function for the number of excited particles follows the three universal distribution laws of extreme value statistics, namely Gumbel, Weibull and Fr\'echet. Implications of this result, as well as general properties of the level density at different energies, are discussed.Comment: 4 pages, no figure

Calotes emma Gray, 1845 (Squamata: Agamidae): range extension and new addition to the reptilian fauna of Tripura, northeast India

Two new records of Calotes emma Gray, 1845, are reported from Srirampur and Homnpui in the state of Tripura, northeast India. These records are the first from Tripura. Present locality records extended the known distribution of C. emma in Southeast Asia. 

Variation in butterfly diversity and unique species richness along different habitats in Trishna Wildlife Sanctuary, Tripura, northeast India

Quantification of butterfly diversity and species richness is of prime importance for evaluating the status of protected areas. Permanent line transect counts were used to record species richness and abundance of butterfly communities of different habitat types in Trishna wildlife sanctuary. A total of 1005 individuals representing 59 species in 48 genera belonging to five families were recorded in the present study. Of these, 23 species belonged to the family Nymphalidae and accounted for 38.98% of the total species and 45.20% of the total number of individuals. Mature secondary mixed moist deciduous forest showed the maximum diversity and species richness, while exotic grassland showed minimum diversity and species richness. Out of 59 species, 31 are new records for Tripura state, while 21 are unique species and nine are listed in the threatened category. This study revealed that mature secondary forests are more important for butterfly communities, while exotic grasslands have a negative impact on species composition

Valuing the social and environmental contribution of woodlands and trees in England, Scotland and Wales. Second edition: to 2018

The first edition of this report is available in ORE: http://hdl.handle.net/10871/25958Woodlands and forests constitute arguably the most diverse environments on earth; diverse not only in terms of the plethora of characteristics and habitats they embrace, but also through the variety of benefits and values that they offer to people. While this diversity of benefits is now widely recognised, incorporating these values into decisions regarding the management and extension of woodland remains a challenge. While the value of some forest products, such as timber, is readily reflected within market prices, this is the exception rather than the rule. Most of the benefits provided by woodlands are not traded through markets and are therefore unpriced public goods. The UK Forestry Commission have for many years directly addressed the problem of incorporating the non-market benefits of woodland within conventional economic decision making through the application of techniques to estimate the economic value of these benefits (e.g. Willis, et al., 2003). As part of this initiative, in 2015 the Forestry Commission began working with the authors of the present report to provide a review of the research, policy and grey literature concerned with the economic valuation of the social and environmental benefits of woodlands and trees. This review, subsequently published as Binner et al., (2017) also included the development of a spreadsheet based decision support tool to facilitate the use of valuation estimates within decision making. The present report provides a second edition of that report, updating both the literature review and the accompanying spreadsheet decision support tool. In preparing this study, the research team at the University of Exeter undertook a structured reviewed of how technical and methodological developments are transforming the potential for robust valuation of non-market benefits and allied decision-making. The methods, data and modelling techniques, which underpin the existing evidence base on the value of woodlands and trees were critically evaluated, so as to provide a practical set of actionable options for enhancing that evidence base and improving decision making

Resistivity due to a Domain Wall in Ferromagnetic Metal

The resistivity due to a domain wall in ferromagnetic metallic wire is calculated based on the linear response theory. The interaction between conduction electrons and the wall is expressed in terms of a classical gauge field which is introduced by the local gauge transformation in the electron spin space. It is shown that the wall contributes to the decoherence of electrons and that this quantum correction can dominate over the Boltzmann resisitivity, leading to a decrease of resisitivity by nucleation of a wall. The conductance fluctuation due to the motion of the wall is also investigated. The results are compared with recent experiments.Comment: 9 pages, 3 figure

X. couchianus and X. hellerii genome models provide genomic variation insight among Xiphophorus species

4 inter-chromosomal rearrangement events between X. hellerii and X. maculatus. (XLSX 40 kb