Subharmonic Generation in Quantum Systems

We show how the classical-quantum correspondence permits long-lived subharmonic motion in a quantum system driven by a periodic force. Exponentially small deviations from exact subharmonicity are due to coherent tunneling between quantized vortex tubes which surround classical elliptic periodic orbits.Comment: 11 pages + 5 figures (available upon request), Revtex 3.0, NSF-ITP-93-4

Comment on "Critique of the foundations of time-dependent density functional theory" [Phys. Rev.A. 75, 022513 (2007)]

A recent paper (Phys. Rev A. 75, 022513 (2007), arXiv:cond-mat/0602020) challenges exact time-dependent density functional theory (TDDFT) on several grounds. We explain why these criticisms are either irrelevant or incorrect, and that TDDFT is both formally exact and predictive.Comment: 4 pages; This is a Comment on the paper cited above, also at arXiv:cond-mat/060202

Time Dependent Floquet Theory and Absence of an Adiabatic Limit

Quantum systems subject to time periodic fields of finite amplitude, lambda, have conventionally been handled either by low order perturbation theory, for lambda not too large, or by exact diagonalization within a finite basis of N states. An adiabatic limit, as lambda is switched on arbitrarily slowly, has been assumed. But the validity of these procedures seems questionable in view of the fact that, as N goes to infinity, the quasienergy spectrum becomes dense, and numerical calculations show an increasing number of weakly avoided crossings (related in perturbation theory to high order resonances). This paper deals with the highly non-trivial behavior of the solutions in this limit. The Floquet states, and the associated quasienergies, become highly irregular functions of the amplitude, lambda. The mathematical radii of convergence of perturbation theory in lambda approach zero. There is no adiabatic limit of the wave functions when lambda is turned on arbitrarily slowly. However, the quasienergy becomes independent of time in this limit. We introduce a modification of the adiabatic theorem. We explain why, in spite of the pervasive pathologies of the Floquet states in the limit N goes to infinity, the conventional approaches are appropriate in almost all physically interesting situations.Comment: 13 pages, Latex, plus 2 Postscript figure

Distribution of ionotropic glutamate receptors and their co-localization with the phosphoprotein DARPP-32 in the medial prefrontal córtex of rats.

O córtex pré-frontal medial (PFCm) é caracterizado por entradas glutamatérgicas e dopaminérgicas que convergem sobre os mesmos neurônios alvos. Devido à escassa informação sobre as bases anatômicas das interações entre a dopamina (DA) e o glutamato (Glu), mapeamos a distribuição de subunidades (Su) de receptores (Rs) de Glu do tipo AMPA, NMDA e kainato no PFCm e investigamos a sua expressão em neurônios contendo a fosfoproteína DARPP-32 e em interneurônios. Os resultados mostram que as Su GluR2/3 dos Rs do tipo AMPA são as mais amplamente distribuídas no PFCm e expressas em todos os neurônios DARPP-32+. GluR2/3 é também amplamente co-localizado com as Su NMDAR1 dos Rs de Glu do tipo NMDA e GluR5/6/7 dos Rs do tipo kainato. Em contraste, as Su GluR1 e GluR4 são somente fracamente expressos no PFCm e não são co-localizados com DARPP-32, porém com GABA ou parvalbumina. Os resultados indicam que as Su GluR2/3, NMDAR1 e GluR5/6/7 são amplamente expressos em neurônios piramidais DARPP-32+ enquanto GluR1 e GluR4 são predominantemente expressos em interneurônios do PFCm.The medial prefrontal cortex (PFCm) is characterized by glutamatergic and dopaminergic afferents that converge on the same target neurons. Since there is only limited information about the anatomical bases for interactions between dopamine (DA) and glutamate (Glu), we mapped the distribution of AMPA, NMDA and kainate Glu receptor (Rs) subunits (Su) in the PFcm and investigated their expression in neurons containing the phosphprotein DARPP-32 and in interneurons. Results show that the Su GluR2/3 of AMPA type Rs are the most prominently distributed in the PFCm and expressed in all neurons DARPP-32+. GluR2/3 is also widely co-localized with the NMDA type Su NMDAR1 and the Kainate Su GluR5/6/7. In contrast, the Su GluR1 and GluR4 are only weakly expressed in the PFCm and are not colocalized with DARPP-32 but with GABA or parvalbumin. Results indicate that the Su GluR2/3, NMDAR1, and GluR5/6/7 are prominently expressed in DARPP-32+ pyramidal neurons, whereas GluR1 and GluR4 are predominantly expressed by interneurons in the PFC

Políticas linguísticas e o processo de ensino-aprendizagem na Guiné-Bissau

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Comunicação e Expressão, Programa de Pós-Graduação em Lingüística, Florianópolis, 2023.O presente trabalho resulta de uma pesquisa explanatória sobre as políticas linguísticas na Guiné- Bissau e suas implicações nas práticas de ensino- aprendizagem guineense. Sendo um país caracterizado por multilinguismo e multiculturalismo, o estudo procura explicitar as relações de poder entre as línguas nesse contexto e o papel intervencionista do Estado sobre a ecologia linguística nacional, especialmente nas práticas institucionais de ensino- aprendizagem do país. No que diz respeito a metodologia, trabalhamos com os documentos oficiais produzidos pelo Estado. Além de investigar os documentos oficiais intervencionistas do Estado guineense sobre línguas no país e seus papeis no sistema ensino-aprendizagem, dedicamos uma atenção especial aos trabalhos de pesquisa produzidos especialmente por pesquisadores guineenses sobre a situação sociopolítico e linguístico do país. Não obstante, para não nos limitarmos a esfera documental e produzir uma leitura equivocada e que possa não dar conta da complexidade da realidade linguística guineense, seguimos o conselho de (CHIFFMAN, 1996. apud. DA SILVA 2013) de que um estudo sério em política linguística, além de considerar o papel de documentos oficiais do Estado sobre as línguas, deve considerar o que as pessoas fazem no cotidiano de vida social. Portanto o conceito de políticas linguísticas in vivo e in vitro (CALVET, 2007) é de grande importância na compreensão e desenvolvimento deste estudo. Neste trabalho a nossa compreensão de política linguística é baseada na definição de (OLIVEIRA, 2016). Encaramos a política linguística como um campo de estudo e igualmente de embate de interesses de grupos ou entidades. O trabalho demonstra que na Guiné-Bissau ainda impera uma visão instrumental e colonial de língua. Conclui-se que é urgente pensar e implementar políticas linguísticas sérias no país. Com base na produção de (RAJAGOPALAN, 2013), salientamos e defendemos fortemente a ideia de que discussões sobre línguas e os seus usos sociais, antes de qualquer coisa, dizem respeito especialmente aos interesses de grupos e a vida de pessoas e grupos que vivem e usam essas línguas. Portanto neste trabalho assumimos uma visão de estudo politicamente explicitada. Com este estudo objetivamos contribuir, não só para a divulgação de conhecimento sobre a visão de estudos em política linguística numa sociedade pós-colonial onde ainda impera uma visão instrumental da língua, mas também contribuir para a criação de políticas linguísticas que considerem os direitos linguísticos de grupos minorizados e socialmente prejudicados, sobretudo no processo ensino-aprendizagem guineense.Abstract: This work is the result of an explanatory research on language policies in Guinea- Bissau and their implications on Guinean teaching-learning practices. Being a country Uncharacterized by multilingualism and multiculturalism, the study seeks to explain the power relations between languages in this context and the interventionist role of the State on the national linguistic ecology, especially in the country's institutional teaching-learning practices. With regard to methodology, we worked with official documents produced by the State. In addition to investigating the official interventionist documents of the Guinean State on languages in the country and their roles in the teaching-learning system, we dedicate special attention to research works produced specifically by Guinean researchers on the socio-political and linguistic situation of the country. However, in order not to limit ourselves to the documentary sphere and produce a mistaken reading that may not account for the complexity of reality, we follow the advice of (CHIFFMAN, 1996. apud. DA SILVA, 2013) that a serious study in language policy, in addition to considering the role of official state documents on languages, it must consider what people do in everyday social life. Therefore, the concept of in vivo and in vitro language policies CALVET (2007) is of great importance in the understanding and development of this study. Here our understanding of language policy is based on the definition of OLIVEIRA (2016). We face language policy as a field of study and also as a clash of interests of groups or entities. Based on RAJAGOPALAN (2013), we emphasize and strongly defend the idea that discussions about languages and their social uses, above all, concern especially the interests of groups and the lives of people and groups who live and use those languages. The work demonstrates that in Guinea-Bissau an instrumental and colonial vision of language still prevails. It is concluded that it is urgent to think and implement healthy language policies in the country. The work demonstrates that in Guinea-Bissau an instrumental and colonial vision of language still prevails. It is concluded that it is urgent to think and implement healthy language policies in the country. Therefore, in this work, we assume a politically explicit vision of the study. With this study we aim to contribute, not only to the dissemination of knowledge about the vision of studies in language policy in a post-colonial society where an instrumental view of language still prevails, but also to contribute to the creation of language policies that respect the linguistic rights of minority and socially disadvantaged groups, especially in the Guinean teaching-learning process

Locally Disordered Lattices in Strong ac Electric Fields

We develop a formalism to study the role of local defects in tight binding systems in the presence of a strong external ac electric field. It is found that the appearance and disappearance of localized states, as well as their localization lengths, can be controlled by the amplitude or frequency of the driving field. The theory is illustrated by numerical model calculations for imperfect semiconductor superlattices in far--infrared laser fields.Comment: LaTeX, 26 pages (8 figures available on request), Preprint UCSBTH-93-2