9 research outputs found
Quantum phases of a spin-1 ultracold Bose gas with three body interactions
We study the effects of both a repulsive and an attractive three body
interaction potential on a spin-1 ultracold Bose gas using mean field approach
(MFA). For an antiferromagnetic (AF) inter- action, we have found the existence
of the odd-even asymmetry in the Mott insulating (MI) lobes in presence of both
the repulsive two and three body interactions. In case of a purely three body
repulsive interaction, the higher order MI lobes stabilize against the
superfluid phase. However, the spin nematic (singlet) formation is restricted
upto the first (second) MI lobes for the former one, while there is neither any
asymmetry nor spin nematic (singlet) formation is observed for the later case.
The results are confirmed after carefully scrutinizing the spin eigen value and
spin nematic order parameter for both the cases. On the other hand, for an
attractive three body interaction, the third MI lobe is predominantly affected,
where it completely engulfs the second and the fourth MI lobes at large values
of the interaction strength. Albeit no significant change is observed beyond
the fourth MI lobe. In the ferromagnetic case, the phase diagram shows similar
features as that of a scalar Bose gas. We have compared our results on the MFA
phase diagrams for both types of the interaction potential via a perturbation
expansion in both the cases.Comment: 8 pages, 7 figure
Ultracold gases in presence of time-dependent synthetic gauge field
We analyze the effect of a time-dependent synthetic magnetic field on the Mott-Insulating (MI) to superfluid (SF) phase transition of a system of bosons via a site decoupling mean-field approach. The synthetic field is incorporated through Peierls coupling that induces a phase shift in the hopping matrix of the Bose-Hubbard model (BHM). We observe that the behavior of critical hopping strength, Jc, vary differently for different time-dependent synthetic fields. The Mott insulating lobe either stabilizes or contracts depending on the nature of the tuning of the time-dependent synthetic field. Also the inclusion of time in the synthetic field destroys the lattice periodicity, however with proper tuning of the time variation of the gauge field, the periodicity can be restored back. Hence the periodicity of the one-dimensional superfluid order parameter is very sensitive to the variation of the time-dependent field. Further, the order parameter either becomes site dependent or independent depending on the nature of the tuning of the these fields. The time-dependent synthetic magnetic field also induces an asymmetry in the discrete energy spectrum of the system which is also clear from the vanishing ‘Butterfly’ pattern of the single particle energy spectrum
Phase Properties of Interacting Bosons in Presence of Quasiperiodic and Random Disorder
Motivated by two different types of disorder that occur in quantum systems
with ubiquity, namely, the random and the quasiperiodic (QP) disorder, we have
performed a systematic comparison of the emerging phase properties
corresponding to these two cases for a system of interacting bosons in a two
dimensional square lattice. Such a comparison is imperative as a random
disorder at each lattice is completely uncorrelated, while a quasiperiodic
disorder is deterministic in nature. Using a site decoupled mean-field
approximation followed by a percolation analysis on a BoseHubbard model,
several different phases are realized, such as the familiar Bose-glass (BG),
Mott insulator (MI), superfluid (SF) phases, and, additionally, we observe a
mixed phase, specific to the QP disorder, which we call as a QM phase.
Incidentally, the QP disorder stabilizes the BG phase more efficiently than the
case of random disorder. Further, we have employed a finite-size scaling
analysis to characterize various phase transitions via computing the critical
transition points and the corresponding critical exponents. The results show
that for both types of disorder, the transition from the BG phase to the SF
phase belongs to the same universality class. However, the QM to the SF
transition for the QP disorder comprises of different critical exponents,
thereby hinting at the involvement of a different universality class therein.
The critical exponents that depict all the various phase transitions occurring
as a function of the disorder strength are found to be in good agreement with
the quantum Monte-Carlo results available in the literature
Entrepreneurial education at university level and entrepreneurship development
Purpose
The purpose of this paper is to contribute to the literature on effectiveness of entrepreneurship education by empirically assessing the role of university entrepreneurial education in entrepreneurship development and reporting the results.
Design/methodology/approach
A quantitative method was applied for this study. This research was preplanned and structured. Based on the previous literature, hypotheses have been developed. The sample is composed on the basis of a simple random sampling and consists of 200 students. The method of data collection was face-to-face interview with a self-administered questionnaire. The data were statistically interpreted using factor and regression analysis.
Findings
The present paper explores and examines the factors and variables of different kinds of entrepreneurial education at the university level. Specifically, at first, this paper addresses the possible entrepreneurial education factors in terms of generalized, motivational, and augmented entrepreneurial education via comprehensive literature review. Second, the paper focuses on the relationship between entrepreneurial education at the university level and entrepreneurship development. The results of this study show a strong positive relationship between different kinds of entrepreneurial education on entrepreneurship development.
Practical implications
The implications of these findings are highly relevant to the universities, policy makers, practitioners, and relevant agencies in regard to their policy-setting process in the entrepreneurship development context. This is because entrepreneurship education at the university level has been recognized to have an impact on student, group, and society. This finding also improves the understanding of donors and development partners about the extent to which a quality entrepreneurship education can play a role in economic development. Wrong specification of research models has a significant impact on research outcome and may even mislead decision-setting process. Therefore, this paper encourages further research that examines the measurement model of these three kinds of entrepreneurial education for entrepreneurship development.
Originality/value
This study provides a first step toward generalized, motivational, and augmented entrepreneurial education at the university level in Bangladesh
mTOR signaling in proteostasis and its relevance to autism spectrum disorders
Proteins are extremely labile cellular components, especially at physiological temperatures. The appropriate regulation of protein levels, or proteostasis, is essential for all cells. In the case of highly polarized cells like neurons, proteostasis is also crucial at synapses, where quick confined changes in protein composition occur to support synaptic activity and plasticity. The accurate regulation of those cellular processes controlling protein synthesis and degradation is necessary for proteostasis, and its deregulation has deleterious consequences in brain function. Alterations in those cellular mechanisms supporting synaptic protein homeostasis have been pinpointed in autism spectrum disorders such as tuberous sclerosis, neurofibromatosis 1, PTEN-related disorders, fragile X syndrome, MECP2 disorders and Angelman syndrome. Proteostasis alterations in these disorders share the alterations in mechanistic/mammalian target of rapamycin (mTOR) signaling pathway, an intracellular pathway with key synaptic roles. The aim of the present review is to describe the recent literature on the major cellular mechanisms involved in proteostasis regulation in the synaptic context, and its association with mTOR signaling deregulations in various autism spectrum disorders. Altogether, the cellular and molecular mechanisms in synaptic proteostasis could be the foundation for novel shared therapeutic strategies that would take advantage of targeting common disorder mechanisms.This review was supported by grant BFU2015-68568-P (MINECO/FEDER, EU) to AO