The one-dimensional Bose-Fermi-Hubbard model in the heavy-fermion limit

We study the phase diagram of the zero-temperature, one-dimensional Bose-Fermi-Hubbard model for fixed fermion density in the limit of small fermionic hopping. This model can be regarded as an instance of a disordered Bose-Hubbard model with dichotomic values of the stochastic variables. Phase boundaries between compressible, incompressible (Mott-insulating) and partially compressible phases are derived analytically within a generalized strong-coupling expansion and numerically using density matrix renormalization group (DMRG) methods. We show that first-order correlations in the partially compressible phases decay exponentially, indicating a glass-type behaviour. Fluctuations within the respective incompressible phases are determined using perturbation theory and are compared to DMRG results.Comment: 11 pages, 15 figures, 2nd, revised versio

Ultracold bosons in disordered superlattices: Mott-insulators induced by tunneling

We analyse the phase diagram of ultra-cold bosons in a one-dimensional superlattice potential with disorder using the time evolving block decimation algorithm for infinite sized systems (iTEBD). For degenerate potential energies within the unit cell of the superlattice loophole-shaped insulating phases with non-integer filling emerge with a particle-hole gap proportional to the boson hopping. Adding a small amount of disorder destroys this gap. For not too large disorder the loophole Mott regions detach from the axis of vanishing hopping giving rise to insulating islands. Thus the system shows a transition from a compressible Bose-glass to a Mott-insulating phase with increasing hopping amplitude. We present a straight forward effective model for the dynamics within a unit cell which provides a simple explanation for the emergence of Mott-insulating islands. In particular it gives rather accurate predictions for the inner critical point of the Bose-glass to Mott-insulator transition

Introduction to special issue of \u3ci\u3eSerials Review\u3c/i\u3e devoted to metrics and scholarly communications

The idea for this issue of Serials Review was developed by the Serials and Other Continuing Resources Section (SOCRS) of the International Federation of Library Associations and Institutions (IFLA). Altmetrics, Bibliometrics, and other types of metrics are areas of special interest and expertise of the section members. For IFLA’s 83rd World Library and Information Conference held in Wrocław, Poland in August 2017, the theme of the SOCRS’s open session was “Altmetrics: It’s Time to Take Action.” Members of SOCRS were reviewers for many of the issue’s articles. The articles are grouped around the following four themes: strategies and tools for metric studies, journal metric case studies, discipline metric analyses, and altmetrics and open access

High School Private Vocational School Learning in West Kalimantan During Physical Distancing COVID-19 in 2020

This study aims to reveal information about the implementation , to overcome obstacles , and the effectiveness of online learning at Senior High Schools (SMA / SMK) in West Kalimantan during Physical Distancing Covid-19 Year 202 0 . I nformation obtained s urvei purposively in nine SMA / SMK (including six elementary schools and four secondary school) in K abupaten Bengkayang, Ketapang, Hedgehog, Melawi, and Sintang West Kalimantan. Respondent teachers were 137 people.The questions that were given to respondents in detail were about the effectiveness of online learning, the media , the resources used, the obstacles faced, and the efforts to overcome these obstacles. The results of descriptive analysis of the teacher's response revealed that the "vast majority" of school (elementary, middle, high school / vocational school) has been carrying out learning online " by effectively" . Teachers plan lessons to combine online and conventional models. Also the facilities used by the teacher generally use cellphones , with the main resources being e-books, journals, videos, and question and answer materials . Learning takes advantage of the application " learning house " , " google for education " , and " own class " . The constraints general are facing is the limited "internet access" and " teacher-student-parent " who has not adaptive learning systems online. To improve e fekti v itas learning teachers make learning fun, attention to needs-style-and the student experience, as well as the evaluation of the continuous. Based on these findings, it is hoped that the government, schools, teachers, students, and parents will prioritize the provision of online learning facilities to be more successful

the Study on the Functionalization Role of Student Parents in Education Activities

This study aims to examine and describe the school's efforts to function the role of students parents in the education process at school. Descriptive research methods are used to achieve the research objectives. The study sample was parents and teachers who were purposively determined on the basis of considering the status of school accreditation. The schools selected as samples were Santun Untan Senior High School (accredited B) and Gembala Baik Senior High School (accreditation A). The research data was collected by interview instruments, questionnaires, and documentation. Data analysis was carried out by descriptive statistical studies to describe the optimal functioning of parents by schools. From the research data obtained the fact that the perceptions of parents of students and teachers in Santun Untan Senior High School and Gembala Baik Senior High School toward the relationship between parents and teachers  are "good." In playing the functions of parents in school, both parents and teachers state "no difficulties." Aspects that are considered "important" to "very important" in fostering parent and teacher relationships include not giving up children's affairs to schools, assuming parents as school partners, parents controlling children's education, parents always following the development of the school , and care about children's education. With this perception, it is possible to "ideal conditions" in building optimal cooperation in student education in the two sample schools

Analytic approximations to the phase diagram of the Jaynes-Cummings-Hubbard model with application to ion chains

We discuss analytic approximations to the ground state phase diagram of the homogeneous Jaynes-Cummings-Hubbard (JCH) Hamiltonian with general short-range hopping. The JCH model describes e.g. radial phonon excitations of a linear chain of ions coupled to an external laser field tuned to the red motional sideband with Coulomb mediated hopping or an array of high-$Q$ coupled cavities containing a two-level atom and photons. Specifically we consider the cases of a linear array of coupled cavities and a linear ion chain. We derive approximate analytic expressions for the boundaries between Mott-insulating and superfluid phases and give explicit expressions for the critical value of the hopping amplitude within the different approximation schemes. In the case of an array of cavities, which is represented by the standard JCH model we compare both approximations to numerical data from density-matrix renormalization group (DMRG) calculations.Comment: 9 pages, 5 figures, extended and corrected second versio