Low-frequency phase diagram of irradiated graphene and periodically driven spin-1/2 XYXY chain

We study the Floquet phase diagram of two-dimensional Dirac materials such as graphene and the one-dimensional (1D) spin-1/2 $XY$ model in a transverse field in the presence of periodic time-varying terms in their Hamiltonians in the low drive frequency ($\omega$) regime where standard $1/\omega$ perturbative expansions fail. For graphene, such periodic time dependent terms are generated via the application of external radiation of amplitude $A_0$ and time period $T = 2\pi/\omega$, while for the 1D $XY$ model, they result from a two-rate drive protocol with time-dependent magnetic field and nearest-neighbor couplings between the spins. Using the adiabatic-impulse method, we provide several semi-analytic criteria for the occurrence of changes in the topology of the phase bands of such systems. For irradiated graphene, we point out the role of the symmetries of $H(t)$ and $U$ behind such topology changes. Our analysis reveals that at low frequencies, phase band topology changes may also happen at $t= T/3, 2T/3$ (apart from $t=T$). We chart out the phase diagrams at $t=T/3, 2T/3,\, {\rm and }\, T$ as a function of $A_0$ and $T$ using exact numerics, and compare them with the prediction of the adiabatic-impulse method. We show that several characteristics of these phase diagrams can be analytically understood from results obtained using the adiabatic-impulse method and point out the crucial contribution of the high-symmetry points in the graphene Brillouin zone to these diagrams. Finally we study the 1D $XY$ model with a two-rate driving protocol using the adiabatic-impulse method and exact numerics revealing a phase band crossing at $t=T/2$ and $k=\pi/2$. We also study the anomalous end modes generated by such a drive. We suggest experiments to test our theory.Comment: v1; 26 pages, 19 Fig

Status of Institutional Repositories in Asian Countries: A Quantitative Study

With the development of information communication technologies, a number of alternative strategies to the traditional scholarly publishing system have been evolved. Among these, Open Access (OA) model which promise to be extremely advantageous to peers everywhere, especially to those who have acute shortage of resources for purchasing scholarly literature. The impetus of OA was boosted by the Open Society Institute (OSI) in a small meeting convened in Budapest on December 1-2, 2001. The purpose of the meeting was to accelerate progress in the international effort to make research literature in all academic fields freely available on the Internet (OAIS, 2002; Hirtle, 2001). The first major international statement on OA, which includes a definition, background information and a list of signatories, is the Budapest Open Access Initiative. The other two leading statements are the Bethesda Statement on Open Access Publishing and the Berlin Declaration on Open Access to Knowledge in the Sciences and Humanities. The conception of open access in these three statements, which is often called the BBB (Budapest, Bethesda and Berlin) definition, launched, inspired, and continues to guide the open access movement. Although institutional-based, or more typically departmental, \u27archives\u27 were known before this, especially in areas such as computer science and economics that were served by NCSTRL and RePEc, respectively, OAI introduced the Protocol for Metadata Harvesting (OAI-PMH) to provide common services that could operate over more general, independent sites (Lynch 2001). Institutional Repository (IR) adopt the same open access and interoperable framework as e-print archive, but rather than being discipline-based, represent the wide range of research output of a given university or research organization. The term was coined by Scholarly Publishing for Academic Resources Coalition (SPARC), and has been defined by SPARC as “digital collections capturing and preserving the intellectual output of a single or multi-university community” (Crow, 2001). Crow argues that institutional digital repositories will lead to significant increases in the prestige of the institutions that build them (Crow, 2002). Stephen Harnad also cites institutional prestige: “Distributed, institution-based self-archiving benefits research institutions in three ways. First, it maximizes the visibility and impact of its own refereed research output. Second, by symmetry, it maximizes their researchers’ access to the full refereed research output of all other institutions. Third, institutions themselves can hasten the transition to self-archiving and so more quickly reduce their library’s annual serials expenditures to 10% (paid to journal publishers for refereeing their submissions)”(Harnad, 2002). Pinfield, Gardner, and MacColl also argue that an e-print archive can raise the profile of an institution (Pinfield, Gardner, & MacColl, 2001)

LIS journals in India: Current status and some improvement measures

The paper identifies the present status of journal publishing in India in the field of library & information science. Identification of journals were made by consulting various sources. The characteristics of the journals have been studied on various parameters like number of years of existence, type of publisher, accessibility, references and citation characteristics, etc. Of the total 72 identified journals, it was observed that almost 70% journals started their publication from 2000 onwards. About 81% journals are available on subscription basis. Print as well as online format for dissemination of research have been adopted by 59% journals, however, 30% journals are still available only in print form. It is seen that private or profit-making (59%) organizations are more interested to publish LIS journals than non-profit making organizations (41%). One of the major drawbacks of Indian LIS journals is there poor visibility and limited coverage in various bibliographical databases. More than 54% journals are not indexed in any important bibliographic database and only 6 journals are indexed in LISA, LISTA or ILSA. The citation statistics of these journals are not satisfactory as 42 journals did not receive any citations for their articles published during 2011-2013. At the end, the study suggests a few measures for improving the quality of journal in LIS domai

Genetic Algorithm-based Design Optimisation of Aperture-coupled Rectangular Microstrip Antenna

The technique of feeding a microstrip antenna with a microstrip line through an aperture is gathering a lot of interest in communication and radar systems used for defence applications.This is due to the fact that this feeding technique has many adjustable parameters in the form of aperture length, width, and stub parameters. This paper presents a study on the effect ofaperture dimensions and stub length on the voltage-standing wave ratio bandwidth of an aperturecoupled microstrip antenna. Without any additional matching network, optimal impedancematching of the antenna has been achieved using genetic algorithm. In the algorithm, each chromosome consists of three binary encoded genes, one for aperture length, second one foraperture width and the last one for stub length. Finally, the algorithm determines the parameters of the antenna that provides the minimum value of the average reflection coefficient. Theinvestigation is made at different microwave frequency ranges and it extends up to Ku band. The results show that the percentage of fractional bandwidth improves for higher design frequencies and has a maximum of 13.2 per cent for centre frequency of 17.5 GHz. Experimental results are presented for a particular range of frequency and the accuracy of the analysis is briefly discussed

Periodically driven Rydberg chains with staggered detuning

We study the stroboscopic dynamics of a periodically driven finite Rydberg chain with staggered ( Δ ) and time-dependent uniform [ λ ( t ) ] detuning terms using exact diagonalization. We show that at intermediate drive frequencies ( ω D ), the presence of a finite Δ results in violation of the eigenstate thermalization hypothesis (ETH) via clustering of Floquet eigenstates. Such clustering is lost at special commensurate drive frequencies for which ℏ ω d = n Δ ( n ∈ Z ) leading to restoration of ergodicity. The violation of ETH in these driven finite-sized chains is also evident from the dynamical freezing displayed by the density-density correlation between Rydberg excitations at even sites of the chain for specific ω D . Such a correlator exhibits stable oscillations with perfect revivals when driven close to the freezing frequencies for initial all spin-down ( | 0 ⟩ ) or Neel ( | Z 2 ⟩ , with up spins on even sites) states. In contrast, for the ∣ ∣ ¯¯¯ Z 2 ⟩ (time-reversed partner of | Z 2 ⟩ ) initial state, we find complete absence of such oscillations leading to freezing for a range of ω D ; this range increases with Δ . We also study the properties of quantum many-body scars in the Floquet spectrum of the model as a function of Δ and show the existence of mid-spectrum scars at large Δ which do not have overlap with either | 0 ⟩ or | Z 2 ⟩ states. We supplement our numerical results with those from an analytic Floquet Hamiltonian computed using Floquet perturbation theory which allows us to provide qualitative analytical explanations of the above-mentioned numerical results

Publication pattern expressed by scientific position, service tenure, and age – A comparative analysis with working women scientists of science and technology laboratories of India

This study investigates the effect of scientific position, service tenure, and age of women scientists of various research laboratories of the Ministry of Science and Technology, Government of India on the research productivity. Drawing on a sample of 902 women scientists of various research laboratories, with their 22,617 publications extracted from Web of Science & Scopus databases, the results show that CSIR scientists have more women per laboratory, DST women scientists have more publication per scientists and DBT women scientists received more citations. The majority of the publications were published by scientists who have post-doctoral or doctorate degrees and most of the papers were published by the women scientists between age 31 and 40. However, per scientist publication reveals that there is a continuous increase of publication with the increase of service and physical age. Therefore, better funding opportunities for young researchers and retaining experienced women scientists for more years may be important to increase women's participation in science

Publication pattern expressed by scientific position, service tenure, and age – A comparative analysis with working women scientists of science and technology laboratories of India

318-325This study investigates the effect of scientific position, service tenure, and age of women scientists of various research laboratories of the Ministry of Science and Technology, Government of India on the research productivity. Drawing on a sample of 902 women scientists of various research laboratories, with their 22,617 publications extracted from Web of Science & Scopus databases, the results show that CSIR scientists have more women per laboratory, DST women scientists have more publication per scientists and DBT women scientists received more citations. The majority of the publications were published by scientists who have post-doctoral or doctorate degrees and most of the papers were published by the women scientists between age 31 and 40. However, per scientist publication reveals that there is a continuous increase of publication with the increase of service and physical age. Therefore, better funding opportunities for young researchers and retaining experienced women scientists for more years may be important to increase women's participation in science