Upcoming Activities

  • December 06, 2018 - 15h

    Colloquium by Prof. Gandhimohan M Viswanathan (UFRN):
    Levy flights and anomalous diffusion in foraging.

    Venue: International Institute of Physics, Natal - RN.

    For more information, please visit the event page.

  • December 2-5, 2018
    Third International Workshop on Ultracold Rydberg Physics

    Venue: Boa Viagem Beach, Recife-PE (Brazil).

    Organizing Committee:
    Rosario Gonzalez Ferez (Universidad de Granada, Spain);
    Tommaso Macrì (Federal University of Rio Grande do Norte, Brazil);
    Emanuel Alves de Lima Henn (University of São Paulo, Brazil);
    Paul Kunz (Army Research Laboratory, USA);
    James P. Shaffer (Quantum Valley Ideas Laboratories, Canada);
    Luis G. Marcassa (University of São Paulo, Brazil).

    To register, please visit the event page.

  • July 15-19, 2019
    Quantum and Classical Systems with Longrange Interactions

    Venue: International Institute of Physics, Natal-RN (Brazil).

    Romain Bachelard (UFSCar, São Carlos-SP);
    Shamik Gupta (Ramakrishna Mission Vivekananda U., India);
    Tommaso Macrì (UFRN, Natal-RN).

    To register, please visit the event page.

Recent Activities

  • Workshop Advances in Quantum Simulation With Ultracold Atoms - 29 OCT-09 NOV 2018
  • Organizers: Prof. Carlos Egues (USP-São Carlos), Prof. Tommaso Macrì

    School: October 29 to November 2.
    Workshop: November 5 to November 9.

    Venue: International Institute of Physics, Natal - RN.

    Leonardo Fallani (University of Florence)
    Tommaso Macrì (UFRN - IIP)
    Christophe Salomon (École Normale Supérieure)
    Luis Santos (University of Hannover)

    Watch all the talks on this link

    Congratulations to Patricia Castilho and Frederick Georg
    for the Best Contributed Talk Prize!

  • Colloquium by Prof. Dan Stamper-Kurn (University of California) - 8 NOV 2018
    • Atoms interacting in interesting lattices

      Atoms moving within the spatially periodic potential generated by interfering plane waves of light can mimic the behavior of electrons that move within the spatially periodic potential within a solid-state crystal. In this manner, neutral atomic gases trapped in optical lattices can serve as an experimental quantum simulator for the physics models that are used to describe electronic materials. I will describe how one can use optical lattices formed using two different colors of light to produce an array of periodic potentials with differing geometry – specifically, two-dimensional lattices with triangular unit cells – and then how interacts modify the correlations of neutral bosonic atoms trapped within those potentials. I will summarize two major experimental findings: a quantitative test of the Bose-Hubbard model achieved by comparing gases trapped in two different trapping geometries, and a characterization of inversion-asymmetric spatial correlations in a trimerized (breathing) kagome lattice. I will conclude with several suggestions for future work. Watch the talk onthis link

  • Colloquium by Prof. Sergei Gukov (Caltech) - 26 OCT 2018
    • Zed-hat

      The goal of this talk, intended for a broader audience, will be to introduce a class of functions that come from physics, answer a question in topology, can be computed via methods more common in the theory of dynamical systems, and in the end turn out to enjoy beautiful modular properties of the type first observed by Ramanujan.

  • Workshop Meet the Editors - Scientific Writing - 1-5 OCT 2018
  • Organizers: Prof. Carlos Egues (USP-São Carlos), Prof. Tommaso Macrì

    First part (October 1-2): University of São Paulo (USP);
    Second part (October 4-5): International Institute of Physics (UFRN).

    Watch all the talks on this link

  • Colloquium by Prof. Rodrigo Capaz (UFRJ) - 13 SEPT 2018
    • Theory of Electrons in 2D Materials and van der Waals Heterostructures

      In this talk, we explore the electronic properties of 2D materials and van der Waals heterostructures, using a combination of ab initio and semi-empirical methods. After reviewing some of the exquisite properties of these novel materials, we focus on 3 recent works: (1) Exotic "hydrogen atoms" in 2D boron nitride; (2) Electronic and optical signatures of trilayer and quadrilayer graphene; and (3) Giant and anisotropic friction in graphene monolayers.

  • Final Report Presentation by Victor Souza (UFRN) - 21 JUNE 2018
    • Estudo de Interações Locais e Soft-Core em Condensados de Bose-Einstein

  • Colloquium by Prof. Mark Warner (University of Cambridge) - 22 MAY 2018
    • Inducing curved metrics in materials gives new mechanics

      Radically novel materials, liquid crystalline elastomers and glasses, change shape by 100s% following changes in temperature or illumination. Shape change, that is elongation along a particular direction, rather than simply change of volume, can be imaginatively arranged induce intrinsic curvature in initially ­ at spaces. The intimate connection between di‑ erential geometry and mechanics comes into play and suggests ways of exploiting light-induced curvature of space for new mechanics paradigms. I will give, with many demonstrations, examples of the geometry arising. These solids can apparently solve the map-maker’s problem of resolving planes with curved space. I will say how this unique property might be exploited in strong actuation.

  • Lecture series on Machine Learning and Deep Learning - 05 MAR-05 MAY 2018
    • Instructors: Prof. Luciano Casarini, Prof. Askery Canabarro.

      For more information, click here.

  • Colloquium by Prof. Eudenilson Albuquerque (UFRN) - 20 MAR 2018
    • Quantum Simulation of Biological Molecules

      The immediate future of pure and applied scientific researches undoubtedly points to the interconnection and complementarity between different areas. It is becoming increasingly less important to approach specific themes, as it was done up to the last century, among which we can highlight the foundations of Quantum Mechanics, the unveil of the molecular structure of DNA with all its consequences, the emergence of semiconductor devices based on silicon and its implication for microelectronics, and the development of purely synthetic drugs. The multidisciplinarity aspect of science, which is becoming more and more present, comes from the maturing of knowledge and the impressive speed of the scientific production, as an output from the performance of research groups in the most diverse areas of scientific knowledge.

      In this context, the field of Nanobiotechnology has emerged as one of the most important research area in recent years. Although scientists still face great difficulties in controlling and manipulating structures at the nanoscale, nature has been performing these tasks with great precision and high efficiency using biological molecules, such as the nucleic acids (DNA/RNA), amino acids and proteins. As a consequence, nowadays there is a great deal of interest to develop theoretical concepts and experimental techniques for self-organized biological systems in search of their technological applications. Biology, Physics and Chemistry, among other areas of knowledge, provide models and mechanisms to promote this approach.

      Thus, the sophisticated molecular recognition of various natural biological materials has been used in the formation of a complex network of structures potentially useful for a variety of optical, electronic, biosensory and pharmaceutical applications. In fact, they offer solutions to many of the obstacles that need to be overcome, since they have the capacity for self-assembly and self-replication, making possible the production of nanostructures with an accuracy that is not feasible within the technologies found in materials science.

      In the above context, we intend to present in this colloquium the main electronic, optical and pharmaceutical properties of some biological molecules and their interactions, using a theoretical/computational framework based on Quantum Mechanics. Investigation of electrical junctions, in which molecular assemblies formed by nucleic acids, amino acids, and proteins act as conductive links of traditional electrical components, will be discussed. Their diversity, versatility and responsiveness to control and manipulation, make them potentially important components not only in nanoelectronic bio-devices (like microRNAs in the early diagnosis of autism), but also as a crucial tool for the efficiency of medicinal drugs ingested by our body, via its binding with the human albumin. We also intend to discuss important aspects related to the biology of cancer using our immunological checking points, specialized proteins that act as brakes in the immune system, allowing it to recognize and attack more efficiently only the cancer cells, avoiding the destruction of healthy cells as in conventional treatments.

  • Colloquium by Prof. Caslav Brukner (University of Vienna) - 27 FEB 2018
    • Causality in a quantum world

      One of the most deeply rooted concepts in science is causality: the idea that events in the present are caused by events in the past and, in turn, act as causes for what happens in the future. If an event A is a cause of an effect B, then B cannot be a cause of A. Physicists, however, suspect that the notion of a definite causal order between events will be untenable in a theory where gravity, and hence the metric field and spatio-temporal distances between events, are subject to quantum mechanical laws. I will review the recent efforts of developing a framework to describe "superpositions of causal order", where one cannot say that A is before or after B, i.e. where the order between events is "indefinite". I will then discuss experimental perspectives for observing such indefinite causal structure and argue that they are useful resources for quantum information processing.

  • Workshop On Long-Range Interactions in Atomic Systems - 5-8 DEC 2017
  • Organizers: E. Henn, T. Macrì, E. Santos, A. Lima, R. Rothganger
    São Carlos Institute of Physics

    For more information, please visit the event website by clicking on the image below

  • Colloquium by Prof. Antonio Acín (ICFO - Barcelona) - 21 NOV 2017
    • Quantum information theory with black boxes

      Device-independent quantum information processing represents a new framework for quantum information applications in which devices are just seen as quantum black boxes processing classical information. This level of abstraction makes device-independent protocols especially relevant for cryptographic applications, as existing quantum hacking attacks become impossible. After introducing the key ideas and concepts needed for the definition of the device-independent scenario, we review the main results and open questions and discuss how these techniques apply to many-body systems.

  • Final Report Presentation by Samihr Hermes (UFRN) - 09 OCT 2017
    • Transferência de estado quântico em cadeias de spins

  • Colloquium by Prof. Paulo Nussenzveig (USP) - 05 OCT 2017
    • Quantum optics on silicon chips

      In recent years, we have seen accelerated progress in the study of quantum phenomena and of their potential applications in information science. Many foundational aspects of quantum mechanics have been tested and/or illustrated in quantum optics experiments. Indeed, light is a natural conveyor of information, not only over large distances but also over the very short distances within computer chips. Silicon photonics has grown from concept to technology in a very short time. Having explored its potential for classical communications, it is only natural to investigate quantum light in these microscopic structures. In this talk, we will discuss a few of the exciting possibilities to generate and manipulate quantum properties of light on silicon chips.

  • Colloquium by Prof. Harold U. Baranger (Duke University) - 19 SEP 2017
    • Nonlinear I-V curve at a quantum critical point produced by dissipation

      Many-body systems that are driven far from equilibrium or simply subjected to quantum noise exhibit complex interplay between the many-body correlations and the external variables, and so are attracting increasing attention. I shall discuss a system that is particularly advantageous for studying these effects: it exhibits impurity quantum criticality, it is amenable to detailed experimental study (and initial experiments have been done), and it is simple enough theoretically that analytical results can be obtained. First, I briefly survey the experimental system and initial results. The system consists of a spin-polarized carbon nanotube quantum dot connected to resistive leads. A quantum critical point (QCP) occurs when a level in the dot is resonant with the leads and the dot is symmetrically coupled to them. Second, I present our calculation of the nonlinear I-V curve at the QCP and show remarkable agreement with the experiment. This result has a simple interpretation as an environmental blockade.

      Watch the talk onthis link

  • Colloquium by Prof. Luiz Davidovich (UFRJ) - 15 AUG 2017
    • Physics, information and the new quantum technologies

      A new quantum technology, developed in several laboratories, has allowed the precise control of individual quantum particles, and has led to a new vision of the notion of information. Bold applications have been considered, based on subtle properties of the quantum world, such as the principle of superposition and entanglement, including cryptography and quantum computing. This colloquium will rreview the conceptual revolution brought about by these recent advances, with emphasis on the close relationship between new theoretical results and possible applications.

      Watch the talk onthis link

  • Colloquium by Prof. Bangalore Sathyaprakasho (Penn State University) - 08 AUG 2017
    • The dawn of gravitational-wave physics and astronomy

      Gravitational wave observations from merging black hole binaries can be used to constrain astrophysical models and test general relativity in dynamical spacetimes. In my talk I will highlight some of the astrophysical implications and bounds on deviations from GR deduced from LIGO's 3.9 detections so far.

  • Colloquium by Prof. Jose Nelson Onuchic (Rice University) - 20 JUNE 2017
    • Funnels and landscapes in protein folding: a historical perspective

      Globally the energy landscape of a folding protein resembles a partially rough funnel. The local roughness of the funnel reflects transient trapping of the protein configurations in local free energy minima. A consequence of minimizing energetic frustration is that the topology of the native fold also plays a major role in the folding mechanism. Some folding motifs are easier to design than others suggesting the possibility that evolution not only selected sequences with sufficiently small energetic frustration but also selected more easily designable native structures. Since protein energy landscapes are in most cases minimally frustrated, structure based models (SMBs) have successfully determined the geometrical features associated with folding and functional transitions. Structural information, however, is limited with respect to different functional configurations. This is a major limitation for SBMs. Alternatively statistical methods to study amino acid co-evolution provide information on residue–residue interactions useful for the study of structure and function. I will show how the combination of these two methods gives rise to a novel way to investigate the mechanisms associated with folding and function.

      Watch the talk onthis link

  • Colloquium by Prof. Marcia Barbosa (UFRGS) - 23 MAY 2017
    • Water: from the ice age to the carbon nanotubes

      In this seminar we discuss some unusual behavior of water. We show how such anomalies are not only important for the maintenance of life, but are also a key element to be used for solving the lack of fresh water problem.

      Watch the talk onthis link

  • Colloquium by Prof. Rogerio Rosenfeld (UNESP) - 17 APR 2017
    • The dark energy survey

      I will describe the ongoing project Dark Energy Survey and show how it can helps us to find the best model that describes our Universe.

  • Colloquium by Prof. Giuseppe Mussardo (SISSA - Italy) - 28 MAR 2017
    • Prime suspects and coprime accomplices: quantum tales in number theory

      Number Theory is a subject full of curiosities, amusing problems and compelling challenges. The purpose of the seminar is to explore — within the context of simple arguments — the rich and elegant interplay that exists between the realms of numbers and the world of quantum mechanics. In particular we discuss a quantum mechanical potential that has, semiclassically, the prime numbers as eigenvalues and the so-called Coprime Quantum Chain, i.e. a strongly correlated lattice system based on the divisibility properties of the occupation numbers of a Bose gas, the exponentially large degeneracy of its ground state and the surprising ability of this quantum system to simulate several different classes of universality, including those of the Ising or the q-state Potts model.

      Watch the talk onthis link

  • Colloquium by Prof. Gerard 't Hooft (Utrecht University) - 22 MAR 2017
    • Black holes as essential ingredients of a quantum gravity theory

      Blach holes are not merely soliton-like structures that have to be taken into account in quantum gravity; including them induces essential modifications of the structure of space and time at the Planck scale. Virtual black holes will change the space-time cosmology in a way that seems not to have been anticipated in string theories.

      Watch the talk onthis link

  • Colloquium by Prof. David R. Nelson (Harvard University) - 17 MAR 2017
    • Gene surfing and survival of the luckiest

      It is widely appreciated that population waves have played a crucial role in the evolutionary history of many species. In parallel with Fokker-Planck descriptions of stochastic processes in physics, population geneticists have developed methods for understanding mutations, genetic drift and selective advantage in such situations. Provided number fluctuations at the frontier are taken into account, neutral genetic markers can be used to infer information about growth, ancestral population size and colonization pathways. Neutral mutations optimally positioned at the front of a growing population wave can increase their abundance via a "surfing" phenomenon. Experimental and theoretical studies of this effect will be presented, as well as recent attempts to extend statistical dynamics ideas to microorganisms cooperating and competing in the turbulent environment of the ocean.

      Watch the talk onthis link

  • Colloquium by Prof. Herch Moysés Nussenzveig (UFRJ-Brazil) - 16 FEB 2017
    • Pinças Óticas: investigando como funciona a vida

      A origem da vida na Terra. Procariontes e Eucariontes. O que é uma pinça ótica. Proteinas motoras: como funcionam. Morfogênese. Mecanobiologia: a interação membrana-citoesqueleto.

  • Seminar by Dr. Giacomo Gori (SISSA - Italy) - 01 DEC 2016 (PROIN-DFTE)
    • One-dimensional long-range percolation

  • Short visit of Prof. Simoni Paganelli - 20-25 NOV 2016
  • Short visit of Dr. Giacomo Gori - 20 NOV-02 DEC 2016
    • Lectures by Dr. Giacomo Gori on bosons trapped in double well potentials (24 and 29 NOV 2016)

  • Focus Workshop on Long-range Interactions with Ultracold Atoms - 21-22 NOV 2016
  • Organizers: M. Giampaolo, T. Macrì, L. Salasnich
    International Institute of Physics, Seminar Room 2

    For more information, please visit the event website by clicking on the image below

  • Visit of Prof. Luca Salasnich (University of Padova) - 11-22 NOV 2016
  • Visit of Prof. Simone Paganelli (University of L'Aquila) - 18-26 NOV 2016
  • Short visit Prof. Márcio Miranda (UFPE) - 28-30 JUNE 2016
    • Colloquium 29 JUNE 2016 (Auditório DFTE)

  • Winter Workshop on Ultracold Matter - 11 JAN 2016
  • Organizers: T. Macrì, L. Salasnich
    Department of Physics and Astronomy Galileo Galilei, Room S

    For more information, please visit the event website by clicking on the image below

Previous Journal Clubs

  • Prof. Rafael Chaves (IIP) - 10 OCT 2016
    • Correlações de Bell em sistemas muitipartidos

      O teorema de Bell demonstra que as correlações obtidas por medições locais em sistemas quânticos emaranhados são incompatíveis com modelos de variáveis ocultas locais. Esse é fenômeno chamado de não-localidade quântica. Neste seminário vamos revisar os elementos básicos no teorema de Bell e discutir algumas das dificuldades em sua comprovação experimental. Na parte final iremos apresentar resultados experimentais recentes onde correlações não-locais foram observadas em um condensado de Bose-Einstein.

  • Prof. Luiz Felipe Pereira (DFTE/UFRN) - 19 SEP 2016
    • Um método muito esperto para calcular a condutividade térmica através de simulações de dinâmica molecular

      Quando uma diferença de temperatura é imposta em um sistema, ela dá origem a um fluxo de calor e os dois estão relacionados pela condutividade térmica através da Lei de Fourier. Este é o método tradicional de calcular a condutividade tanto experimentalmente quanto por simulações de dinâmica molecular. Em 1996, Florian Müller-Plathe, então postdoc no Max Planck Institute for Polymer Research, propôs um novo método para calcular a condutividade térmica através de simulações de dinâmica molecular fora do equilíbrio. No método reverso proposto por Müller-Plathe, um fluxo de calor é imposto no sistema trocando a energia cinética de partículas em regiões diferentes, originando uma diferença de temperatura. Apesar de ser um método completamente artificial, a proposta de Müller-Plathe apresenta uma série de vantagens sobre o método tradicional: é muito simples de implementar, é compatível com as condições de contorno periódicas, conserva a energia total e o momento linear e a convergência é mais rápida. Inicialmente, o método foi testado em um fluido descrito pelo potencial de Lennard-Jones e desde então foi utilizado em centenas de outros sistemas, incluindo trabalhos recentes do Grupo de Transporte em Nanoestruturas do DFTE. O artigo original descrevendo o método reverso de Müller-Plathe já foi citado mais de 460 vezes de acordo com a plataforma Web of Science.

  • Dr. Massimo Ostilli (UFRN) - 22 AUG 2016
    • Termalização de sistemas quânticos de muitos corpos

      Compreender e quantificar a termalização de um sistema quântico aberto, envolve a teoria avançada de semigroups quânticos. A Equação de Lindblad, que resulta de uma abordagem puramente matemática, é bem conhecida entre os especialistas da área, mas muitas vezes é vista como demasiado abstrata e confundida com o seu homólogo microscópico, a Quantum Optical Master Equation (QOME), uma equação derivada pelos físicos. Nesta palestra, iremos discutir brevemente as duas abordagens. Iremos ilustrar como usar corretamente a Equação de Lindblad, e como ela corretamente descreve a física esperada. Acontece que, no geral, a equação resultante, não é equivalente à QOME, e que a QOME pode levar a resultados não físicos quando aplicada a sistemas extensos.

  • Prof. Rodrigo Pereira (IIP) - 08 AUG 2016
    • Fases topológicas em gases ultra frios

      Muitas fases topológicas descobertas em matéria condensada podem ser realizadas também em sistemas de átomos frios em redes óticas. Neste seminário vamos discutir alguns avanços recentes nesta área, onde o foco principal será discutir como o movimento de uma nuvem atômica, sujeita a uma força externa, permite medir o número de Chern, um invariante topológico que caracteriza fases do efeito Hall quântico.

  • Prof. Leandro do Nascimento (IIP) - 30 MAY 2016
    • Fracionalização de Carga e Topologia no Modelo SSH (Su, Schrieffer e Heeger)

      O modelo SSH descreve elétrons em uma cadeia undimensional. Este pode ser aplicado na descrição do poliacetileno que consiste de uma cadeia formada por átomos de carbono e hidrogênio com hibridização sp2. Sabe-se que nesse tipo de sistema é energeticamente favorável a formação de um estado dimerizado, no qual os átomos ocupam uma posição fora do equilíbrio. Neste seminário discutiremos alguns aspectos do modelo SSH: a) Relação com a teoria de Dirac em baixas energias; b) Existência de estados com energia zero como consequência de uma fase com winding number diferente de zero; c) Fracionalização de carga como consequência direta desses estados de energia nula.

  • Prof. Francisco da Costa (UFRN) - 16 MAY 2016
    • Comportamento tricrítico em vidro de spins

      O ponto tricrítico é essencialmente o lugar de encontro entre o fim de uma linha de coexistência e uma linha crítica em um diagrama de fases bidimensional. Vamos discutir alguns problemas, a maior parte dos quais em aberto, sobre o comportamento tricrítico em sistemas desordenados. Em particular, veremos que no caso dos vidros de spins ainda não dispomos de uma teoria de Landau apropriada.

  • Prof. Jacopo Viti (UFRN) - 2 MAY 2016
    • Emaranhamento e entropia de emaranhamento: uma mini-introdução

      Nesta palestra introduzirei o conceito de emaranhamento em mecânica quântica, fornecendo uma definição formal e discutindo brevemente os aspectos contra-intuitivos deste fenómeno. Mostrarei como medir o emaranhamento em estados quânticos puros por meio da entropia de Von Neumann e concluirei com algumas considerações sobre a importância da entropia de emaranhamento no estudo dos sistemas físicos com muitas partículas.

  • Prof. Leonardo Dantas - 18 APR 2016
    • Cálculos de energia livre utilizando dinâmica molecular

      Obter a energia livre de um sistema é uma tarefa de grande importância em termodinâmica. Dentre as informações que podem ser obtidas a partir de seu conhecimento estão: se uma reação química é espontânea ou não; se um soluto é hidrofóbico ou hidrofílico; qual a estabilidade relativa de diversas fases de um material; qual a estabilidade relativa de diversas conformações de uma molécula; qual a viabilidade farmacêutica de certos compostos terapêuticos. Entretanto, obter a função de partição analiticamente nem sempre é possível. Ferramentas computacionais, como o método de Monte Carlo, podem ajudar nesses casos. Neste Journal Club será mostrado como o método da Dinâmica Molecular pode ser usada para se obter diferenças de energia livre numericamente. Primeiramente discutiremos os métodos perturbativos e de troca adiabática [1] para ilustrar o uso da metodologia. A Dinâmica Molecular pode ser usada para se obter médias temporais de grandezas de interesse. Porém, para que estes resultados possam ser usados em mecânica estatística, é preciso que a hipótese Ergódica seja observada. É preciso para isto uma simulação com duração suficiente para que se obtenha uma boa amostragem do espaço de fase. Realizar uma boa amostragem é particularmente difícil quando a superfície de energia potencial apresenta ou um grande número de mínimos ou barreiras de energia separando mínimos importantes. Para garantir uma boa amostragem do espaço de fase a um custo computacional razoável nestes casos, os chamados Ensembles Generalizados [2] foram desenvolvidos. Discutiremos brevemente três destes algoritmos: (i) o multicanônico, (ii) o da têmpera simulada e (iii) o método da troca de réplicas.

  • Victor Souza - 28 MAR 2016
    • Efeito Zeno quântico e algumas realizações experimentais

      A evolução dinâmica de um estado quântico inicial pode ser freada, e até interrompida, caso ele seja a submetido a frequentes e rápidas medições, como argumentado por Misra e Sudarshan em 1977. O intervalo de tempo da evolução do sistema que permite esse efeito e, também, o próprio efeito foram batizados por eles de “Zeno”, em alusão ao paradoxo grego da flecha de Zeno que nunca alcançaria seu alvo ao ser continuamente observada. Regularmente são produzidos artigos tratando desse tema e de possíveis aplicações para o fenômeno, e neste Journal Club serão citados alguns artigos recentes que demonstraram esse efeito experimentalmente.

  • Prof. Dmitry Melnikov (IIP) - 14 MAR 2016
    • Entropia de emaranhamento como uma janela para gravitação quântica

      Teoria de cordas pretende providenciar interpretações geométricas para vários fenômenos de física quântica. Em um trabalho célebre, Shinsei Ryu e Tadashi Takayanagi sugeriram uma definição da entropia de emaranhamento como áreas de superfícies mínimas em espaço anti-de Sitter, muito familiar aos modelos holográficos em teoria de cordas. A proposta de Ryu-Takayanagi é consistente com as propriedades conhecidas da entropia e oferece uma perspectiva imprevista para as fundações de gravitação quântica.

  • Prof. Fabio Novaes (IIP) - 29 FEB 2016
    • Termodinâmica e Mecânica Estatística de Buracos Negros

      Buracos negros são entendidos como sistemas térmicos desde a descoberta da radiação Hawking na década de 70. Estando um buraco negro acoplado a um vácuo quântico, o mesmo irradia como um corpo negro, tornando possível definir uma noção de equilíbrio, temperatura e entropia para este misterioso sistema físico. Com uma entropia bem definida, surge a questão: é possível descrever os microestados quânticos de um buraco negro e a emergência de suas leis termodinâmicas macroscópicas? Neste seminário, apresentaremos as leis da termodinâmica de um buraco negro e algumas teorias candidatas para sua descrição estatística.

  • Prof. Sergio Rodriguez (UFRN) - 15 FEB 2016
    • Verificação experimental contundente da violação das desigualdades de Bell

      Em 1935, Einstein, Podolsky e Rosen publicaram um artigo que questionava a completude da mecânica quântica como teoria física. Eles argumentaram que esta não satisfazia certos critérios de “realismo” e “localidade”. Este questionamento deu lugar a um debate que permaneceu no âmbito filosófico durante décadas, até que em 1964 John Bell descobriu uma maneira, através de suas célebres desigualdades, de verificar experimentalmente se a realidade física obedece ou não a uma teoria realista local. Em 2015 foram realizados três experimentos, de maneira independente, que verificaram de forma contundente a violação das desigualdades de Bell. Neste Journal Club debateremos sobre um desses experimentos, realizado com fótons emaranhados. Discutiremos a forma em que foram removidos simultaneamente os principais “furos” que ainda davam lugar a interpretações em termos de uma teoria realista local.

  • Prof. Luciano da Silva (UFRN) - 07 DEC 2015
    • Roles of dimensionality of complex networks with metrics: connections with nonextensive mechanics

      Networks are observed in many fields of science, from social sciences to physics, from biology to economics, to cite but a few. In 2005 it was proposed (Soares, Tsallis, Mariz and Silva) a two-dimensional geographic network model with preferential attachment given by [1]. This model exhibits competition between metric neighborhood and connectivity. A connection was exhibited between scale-free networks and nonextensive statistics. We now look for possible universal scaling laws in this model. How would the value of the index q of the connectivity distribution depend on the dimension dand the index characterizing the range? In this work we numerically analyze the geographic growth model network at various dimensions (d=1,2,3,4) and verify the existence of a law of corresponding states, more precisely that the index q(d) can be written as a function of the single variable.

  • Prof. Roberto Teodoro - 23 NOV 2015
    • Um convite à percolação

      Nesse breve colóquio vou apresentar o que é a percolação e quais as principais questões que levanta. Apresentarei problemas e modelos de interesse atual.

  • Prof. João Medeiros (UFRN) - 16 NOV 2015
  • Prof. Gandhi Viswanathan (UFRN) - 26 OCT 2015
  • Prof. Tommaso Macrì (UFRN) - 05 OCT 2015