March 2019 - Materia-seminarios

Recordatorio de seminario: Non-equilibrium absorbing state phase transition in open quantum spin chains
by Daniel Manzano 21 Mar '19

21 Mar '19

El Grupo de Física Estadística y de los Sistemas Complejos les invita al siguiente seminario. Ponente: Federico Carollo, University of Nottingham. Título: Non-equilibrium absorbing state phase transition in open quantum spin chains Abstract: The contact process is a paradigmatic classical stochastic system displaying critical behaviour even in one dimension. It features a non-equilibrium phase transition into an absorbing state that has been widely investigated and shown to belong to the directed percolation universality class. On the contrary, when the process is considered in a quantum regime much less has been established. Only semi-classical studies have been conducted and even the nature of the transition in low dimensions is still debated. Also from a numerical point of view, from which the system looks fairly simple - especially in one dimension - results are lacking. The presence of the absorbing state poses a substantial challenge which appears to affect the reliability of algorithms targeting directly the steady-state. Here we perform real-time numerical simulations of the open dynamics of the quantum contact process and shed light on the existence and on the nature of an absorbing state phase transition in one dimension. We find evidence for the transition being continuous and provide first estimates for the critical exponents. Fecha y hora: Viernes 22 de Marzo. 11:00. Lugar: Seminario de Física Estadística. Primera Planta del edificio de Física. Facultad de Ciencias. Atentamente. --------------------------------------------------------------------------------- Daniel Manzano Electromagnetism and Condensed Matter Department University of Granada Facultad de Ciencias, Av. Fuentenueva s/n Granada 18071, Spain Phone: +34 958241000 Ext: 20569 http://ic1.ugr.es/manzano/ <http://ic1.ugr.es/manzano/>

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Seminario: Non-equilibrium absorbing state phase transition in open quantum spin chains
by Daniel Manzano 18 Mar '19

18 Mar '19

El Grupo de Física Estadística y de los Sistemas Complejos les invita al siguiente seminario. Ponente: Federico Carollo, University of Nottingham. Título: Non-equilibrium absorbing state phase transition in open quantum spin chains Abstract: The contact process is a paradigmatic classical stochastic system displaying critical behaviour even in one dimension. It features a non-equilibrium phase transition into an absorbing state that has been widely investigated and shown to belong to the directed percolation universality class. On the contrary, when the process is considered in a quantum regime much less has been established. Only semi-classical studies have been conducted and even the nature of the transition in low dimensions is still debated. Also from a numerical point of view, from which the system looks fairly simple - especially in one dimension - results are lacking. The presence of the absorbing state poses a substantial challenge which appears to affect the reliability of algorithms targeting directly the steady-state. Here we perform real-time numerical simulations of the open dynamics of the quantum contact process and shed light on the existence and on the nature of an absorbing state phase transition in one dimension. We find evidence for the transition being continuous and provide first estimates for the critical exponents. Fecha y hora: Viernes 22 de Marzo. 11:00. Lugar: Seminario de Física Estadística. Primera Planta del edificio de Física. Facultad de Ciencias. Atentamente. --------------------------------------------------------------------------------- Daniel Manzano Electromagnetism and Condensed Matter Department University of Granada Facultad de Ciencias, Av. Fuentenueva s/n Granada 18071, Spain Phone: +34 958241000 Ext: 20569 http://ic1.ugr.es/manzano/ <http://ic1.ugr.es/manzano/>

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Recordatorio de seminario: Noise-induced activity suppression in nature: experiments and theory
by Daniel Manzano 12 Mar '19

12 Mar '19

Día y hora: Viernes 15 de Marzo, 12:00 horas. Titulo: Noise-induced activity suppression in nature: experiments and theory Ponente: Prof. Joaquín J. Torres. Universidad de Granada. Abstract: The inverse stochastic resonance (ISR) phenomenon consists in an unexpected suppression in the activity of a natural system under the influence of noise. First evidence such noise induced activity supression has been observed in the pacemaker activity of the squid giant axon in the presence of moderate values of noise. A possible requirement for this phenomenon is the existence of a bistable regime in the behavior of the system. The first experimental demonstration of ISR has been recently reported in an in vitro preparation of a cerebral purkinje cells. Also in a recent work, we have demonstrated that ISR not only emerges in a single neuron but also it can appear in neuronal populations and in the presence of short-term synaptic plasticity. In this last case, synaptic noise can induce double ISR behaviour. On the other hand, the recent report of ISR behaviour in other systems such as in nematic liquid cristals and ecological systems indicate that ISR is a very general emerging phenomenon in nature. Then, in this talk, I report a general theoretical framework we recently developed to explain the possible emergence of ISR in a general bistable system, and conclude on conditions the potential function which drives the dynamics must accomplish. We show that such an intriguing, and apparently widely observed, phenomenon ensues in the case of an asymmetric potential function when the high activity minimum state of the system is metastable with the largest basin of attraction and the low activity state is the global minimum with a smaller basin of attraction. We will discuss on the relevance of such a picture to understand the ISR features and to predict its general appearance in other natural systems that share the requirements described here. Finally, I report another intriguing non-standard stochastic resonance in our system, which occurs in the absence of any weak signal input into the system and whose emergence can be explained, with the ISR, within our theoretical framework in terms of the shape of the potential function. Un saludo. --------------------------------------------------------------------------------- Daniel Manzano Electromagnetism and Condensed Matter Department University of Granada Facultad de Ciencias, Av. Fuentenueva s/n Granada 18071, Spain Phone: +34 958241000 Ext: 20569 http://ic1.ugr.es/manzano/ <http://ic1.ugr.es/manzano/> --------------------------------------------------------------------------------- Daniel Manzano Electromagnetism and Condensed Matter Department University of Granada Facultad de Ciencias, Av. Fuentenueva s/n Granada 18071, Spain Phone: +34 958241000 Ext: 20569 http://ic1.ugr.es/manzano/ <http://ic1.ugr.es/manzano/>

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Seminario:
by Daniel Manzano 11 Mar '19

11 Mar '19

Hola a todos. El seminario del Viernes será finalmente a la hora habitual las 12:00. Datos: Día y hora: Viernes 8 de Marzo, 12:00 horas. Titulo: Noise-induced activity suppression in nature: experiments and theory Ponente: Prof. Joaquín J. Torres. Universidad de Granada. Abstract: The inverse stochastic resonance (ISR) phenomenon consists in an unexpected suppression in the activity of a natural system under the influence of noise. First evidence such noise induced activity supression has been observed in the pacemaker activity of the squid giant axon in the presence of moderate values of noise. A possible requirement for this phenomenon is the existence of a bistable regime in the behavior of the system. The first experimental demonstration of ISR has been recently reported in an in vitro preparation of a cerebral purkinje cells. Also in a recent work, we have demonstrated that ISR not only emerges in a single neuron but also it can appear in neuronal populations and in the presence of short-term synaptic plasticity. In this last case, synaptic noise can induce double ISR behaviour. On the other hand, the recent report of ISR behaviour in other systems such as in nematic liquid cristals and ecological systems indicate that ISR is a very general emerging phenomenon in nature. Then, in this talk, I report a general theoretical framework we recently developed to explain the possible emergence of ISR in a general bistable system, and conclude on conditions the potential function which drives the dynamics must accomplish. We show that such an intriguing, and apparently widely observed, phenomenon ensues in the case of an asymmetric potential function when the high activity minimum state of the system is metastable with the largest basin of attraction and the low activity state is the global minimum with a smaller basin of attraction. We will discuss on the relevance of such a picture to understand the ISR features and to predict its general appearance in other natural systems that share the requirements described here. Finally, I report another intriguing non-standard stochastic resonance in our system, which occurs in the absence of any weak signal input into the system and whose emergence can be explained, with the ISR, within our theoretical framework in terms of the shape of the potential function. Un saludo. --------------------------------------------------------------------------------- Daniel Manzano Electromagnetism and Condensed Matter Department University of Granada Facultad de Ciencias, Av. Fuentenueva s/n Granada 18071, Spain Phone: +34 958241000 Ext: 20569 http://ic1.ugr.es/manzano/ <http://ic1.ugr.es/manzano/>

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Cambio de día. Seminario: Noise-induced activity suppression in nature: experiments and theory
by Daniel Manzano 07 Mar '19

07 Mar '19

Les avisamos del cambio de día del siguiente seminario. Día y hora: Viernes 15 de Marzo, 11:00 horas. Lugar: Aula de ordenadores, Departamento de Física de la Materia (planta baja del edificio de física) Ponente: Prof. Joaquín J. Torres Titulo: Noise-induced activity suppression in nature: experiments and theory Abstract: The inverse stochastic resonance (ISR) phenomenon consists in an unexpected suppression in the activity of a natural system under the influence of noise. First evidence such noise induced activity supression has been observed in the pacemaker activity of the squid giant axon in the presence of moderate values of noise. A possible requirement for this phenomenon is the existence of a bistable regime in the behavior of the system. The first experimental demonstration of ISR has been recently reported in an in vitro preparation of a cerebral purkinje cells. Also in a recent work, we have demonstrated that ISR not only emerges in a single neuron but also it can appear in neuronal populations and in the presence of short-term synaptic plasticity. In this last case, synaptic noise can induce double ISR behaviour. On the other hand, the recent report of ISR behaviour in other systems such as in nematic liquid cristals and ecological systems indicate that ISR is a very general emerging phenomenon in nature. Then, in this talk, I report a general theoretical framework we recently developed to explain the possible emergence of ISR in a general bistable system, and conclude on conditions the potential function which drives the dynamics must accomplish. We show that such an intriguing, and apparently widely observed, phenomenon ensues in the case of an asymmetric potential function when the high activity minimum state of the system is metastable with the largest basin of attraction and the low activity state is the global minimum with a smaller basin of attraction. We will discuss on the relevance of such a picture to understand the ISR features and to predict its general appearance in other natural systems that share the requirements described here. Finally, I report another intriguing non-standard stochastic resonance in our system, which occurs in the absence of any weak signal input into the system and whose emergence can be explained, with the ISR, within our theoretical framework in terms of the shape of the potential function. Atentamente, --------------------------------------------------------------------------------- Daniel Manzano Electromagnetism and Condensed Matter Department University of Granada Facultad de Ciencias, Av. Fuentenueva s/n Granada 18071, Spain Phone: +34 958241000 Ext: 20569 http://ic1.ugr.es/manzano/ <http://ic1.ugr.es/manzano/>

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Seminario: Noise-induced activity suppression in nature: experiments and theory
by Daniel Manzano 04 Mar '19

04 Mar '19

Hola a todos. El próximo seminario será impartido por el Profesor Joaquín Torres. Estos son los datos: Día y hora: Viernes 8 de Marzo, 11:00 horas. Titulo: Noise-induced activity suppression in nature: experiments and theory Abstract: The inverse stochastic resonance (ISR) phenomenon consists in an unexpected suppression in the activity of a natural system under the influence of noise. First evidence such noise induced activity supression has been observed in the pacemaker activity of the squid giant axon in the presence of moderate values of noise. A possible requirement for this phenomenon is the existence of a bistable regime in the behavior of the system. The first experimental demonstration of ISR has been recently reported in an in vitro preparation of a cerebral purkinje cells. Also in a recent work, we have demonstrated that ISR not only emerges in a single neuron but also it can appear in neuronal populations and in the presence of short-term synaptic plasticity. In this last case, synaptic noise can induce double ISR behaviour. On the other hand, the recent report of ISR behaviour in other systems such as in nematic liquid cristals and ecological systems indicate that ISR is a very general emerging phenomenon in nature. Then, in this talk, I report a general theoretical framework we recently developed to explain the possible emergence of ISR in a general bistable system, and conclude on conditions the potential function which drives the dynamics must accomplish. We show that such an intriguing, and apparently widely observed, phenomenon ensues in the case of an asymmetric potential function when the high activity minimum state of the system is metastable with the largest basin of attraction and the low activity state is the global minimum with a smaller basin of attraction. We will discuss on the relevance of such a picture to understand the ISR features and to predict its general appearance in other natural systems that share the requirements described here. Finally, I report another intriguing non-standard stochastic resonance in our system, which occurs in the absence of any weak signal input into the system and whose emergence can be explained, with the ISR, within our theoretical framework in terms of the shape of the potential function. Un saludo. --------------------------------------------------------------------------------- Daniel Manzano Electromagnetism and Condensed Matter Department University of Granada Facultad de Ciencias, Av. Fuentenueva s/n Granada 18071, Spain Phone: +34 958241000 Ext: 20569 http://ic1.ugr.es/manzano/ <http://ic1.ugr.es/manzano/>

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