The Experts below are selected from a list of 4521 Experts worldwide ranked by ideXlab platform
Daniel Domínguez - One of the best experts on this subject based on the ideXlab platform.
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Langevin simulations of the out-of-equilibrium dynamics of vortex glasses in high-temperature superconductors
Physical Review B, 2007Co-Authors: Sebastian Bustingorry, Leticia F. Cugliandolo, Daniel DomínguezAbstract:We study the relaxation dynamics of flux lines in dirty high-temperature superconductors using numerical simulations of a London-Langevin model of the interacting vortex lines. By analysing the equilibrium dynamics in the vortex liquid phase we find a dynamic crossover to a glassy non-equilibrium regime. We then focus on the out-of-equilibrium dynamics of the vortex glass phase using tools that are common in the study of other glassy systems. By monitoring the two-times roughness and dynamic wandering we identify and characterize finite-size effects that are similar, though more complex, than the ones found in the stationary roughness of clean interface dynamics. The two-times density-density correlation and mean-squared-displacement correlation age and their temporal scaling follows a Multiplicative Law similar to the one found at criticality. The linear responses also age and the comparison with their associated correlations shows that the equilibrium fluctuation-dissipation relation is modified in a simple manner that allows for the identification of an effective temperature characterizing the dynamics of the slow modes. The effective temperature is closely related to the vortex liquid-vortex glass crossover temperature. Interestingly enough, our study demonstrates that the glassy dynamics in the vortex glass is basically identical to the one of a single elastic line in a disordered environment (with the same type of scaling though with different parameters). Possible extensions and the experimental relevance of these results are also discussed.
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Langevin simulations of the out-of-equilibrium dynamics of the vortex glass in high-temperature superconductors
Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2007Co-Authors: Sebastian Bustingorry, Leticia F. Cugliandolo, Daniel DomínguezAbstract:We study the relaxation dynamics of flux lines in dirty high-temperature superconductors using numerical simulations of a London-Langevin model of the interacting vortex lines. By analysing the equilibrium dynamics in the vortex liquid phase we find a dynamic crossover to a glassy non-equilibrium regime. We then focus on the out-of-equilibrium dynamics of the vortex glass phase using tools that are common in the study of other glassy systems. By monitoring the two-times roughness and dynamic wandering we identify and characterize finite-size effects that are similar, though more complex, than the ones found in the stationary roughness of clean interface dynamics. The two-times density-density correlation and mean-squared-displacement correlation age and their temporal scaling follows a Multiplicative Law similar to the one found at criticality. The linear responses also age and the comparison with their associated correlations shows that the equilibrium fluctuation-dissipation relation is modified in a simple manner that allows for the identification of an effective temperature characterizing the dynamics of the slow modes. The effective temperature is closely related to the vortex liquid-vortex glass crossover temperature. Interestingly enough, our study demonstrates that the glassy dynamics in the vortex glass is basically identical to the one of a single elastic line in a disordered environment (with the same type of scaling though with different parameters). Possible extensions and the experimental relevance of these results are also discussed.
Sebastian Bustingorry - One of the best experts on this subject based on the ideXlab platform.
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Langevin simulations of the out-of-equilibrium dynamics of vortex glasses in high-temperature superconductors
Physical Review B, 2007Co-Authors: Sebastian Bustingorry, Leticia F. Cugliandolo, Daniel DomínguezAbstract:We study the relaxation dynamics of flux lines in dirty high-temperature superconductors using numerical simulations of a London-Langevin model of the interacting vortex lines. By analysing the equilibrium dynamics in the vortex liquid phase we find a dynamic crossover to a glassy non-equilibrium regime. We then focus on the out-of-equilibrium dynamics of the vortex glass phase using tools that are common in the study of other glassy systems. By monitoring the two-times roughness and dynamic wandering we identify and characterize finite-size effects that are similar, though more complex, than the ones found in the stationary roughness of clean interface dynamics. The two-times density-density correlation and mean-squared-displacement correlation age and their temporal scaling follows a Multiplicative Law similar to the one found at criticality. The linear responses also age and the comparison with their associated correlations shows that the equilibrium fluctuation-dissipation relation is modified in a simple manner that allows for the identification of an effective temperature characterizing the dynamics of the slow modes. The effective temperature is closely related to the vortex liquid-vortex glass crossover temperature. Interestingly enough, our study demonstrates that the glassy dynamics in the vortex glass is basically identical to the one of a single elastic line in a disordered environment (with the same type of scaling though with different parameters). Possible extensions and the experimental relevance of these results are also discussed.
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Langevin simulations of the out-of-equilibrium dynamics of the vortex glass in high-temperature superconductors
Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2007Co-Authors: Sebastian Bustingorry, Leticia F. Cugliandolo, Daniel DomínguezAbstract:We study the relaxation dynamics of flux lines in dirty high-temperature superconductors using numerical simulations of a London-Langevin model of the interacting vortex lines. By analysing the equilibrium dynamics in the vortex liquid phase we find a dynamic crossover to a glassy non-equilibrium regime. We then focus on the out-of-equilibrium dynamics of the vortex glass phase using tools that are common in the study of other glassy systems. By monitoring the two-times roughness and dynamic wandering we identify and characterize finite-size effects that are similar, though more complex, than the ones found in the stationary roughness of clean interface dynamics. The two-times density-density correlation and mean-squared-displacement correlation age and their temporal scaling follows a Multiplicative Law similar to the one found at criticality. The linear responses also age and the comparison with their associated correlations shows that the equilibrium fluctuation-dissipation relation is modified in a simple manner that allows for the identification of an effective temperature characterizing the dynamics of the slow modes. The effective temperature is closely related to the vortex liquid-vortex glass crossover temperature. Interestingly enough, our study demonstrates that the glassy dynamics in the vortex glass is basically identical to the one of a single elastic line in a disordered environment (with the same type of scaling though with different parameters). Possible extensions and the experimental relevance of these results are also discussed.
Leticia F. Cugliandolo - One of the best experts on this subject based on the ideXlab platform.
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Langevin simulations of the out-of-equilibrium dynamics of vortex glasses in high-temperature superconductors
Physical Review B, 2007Co-Authors: Sebastian Bustingorry, Leticia F. Cugliandolo, Daniel DomínguezAbstract:We study the relaxation dynamics of flux lines in dirty high-temperature superconductors using numerical simulations of a London-Langevin model of the interacting vortex lines. By analysing the equilibrium dynamics in the vortex liquid phase we find a dynamic crossover to a glassy non-equilibrium regime. We then focus on the out-of-equilibrium dynamics of the vortex glass phase using tools that are common in the study of other glassy systems. By monitoring the two-times roughness and dynamic wandering we identify and characterize finite-size effects that are similar, though more complex, than the ones found in the stationary roughness of clean interface dynamics. The two-times density-density correlation and mean-squared-displacement correlation age and their temporal scaling follows a Multiplicative Law similar to the one found at criticality. The linear responses also age and the comparison with their associated correlations shows that the equilibrium fluctuation-dissipation relation is modified in a simple manner that allows for the identification of an effective temperature characterizing the dynamics of the slow modes. The effective temperature is closely related to the vortex liquid-vortex glass crossover temperature. Interestingly enough, our study demonstrates that the glassy dynamics in the vortex glass is basically identical to the one of a single elastic line in a disordered environment (with the same type of scaling though with different parameters). Possible extensions and the experimental relevance of these results are also discussed.
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Langevin simulations of the out-of-equilibrium dynamics of the vortex glass in high-temperature superconductors
Physical Review B: Condensed Matter and Materials Physics (1998-2015), 2007Co-Authors: Sebastian Bustingorry, Leticia F. Cugliandolo, Daniel DomínguezAbstract:We study the relaxation dynamics of flux lines in dirty high-temperature superconductors using numerical simulations of a London-Langevin model of the interacting vortex lines. By analysing the equilibrium dynamics in the vortex liquid phase we find a dynamic crossover to a glassy non-equilibrium regime. We then focus on the out-of-equilibrium dynamics of the vortex glass phase using tools that are common in the study of other glassy systems. By monitoring the two-times roughness and dynamic wandering we identify and characterize finite-size effects that are similar, though more complex, than the ones found in the stationary roughness of clean interface dynamics. The two-times density-density correlation and mean-squared-displacement correlation age and their temporal scaling follows a Multiplicative Law similar to the one found at criticality. The linear responses also age and the comparison with their associated correlations shows that the equilibrium fluctuation-dissipation relation is modified in a simple manner that allows for the identification of an effective temperature characterizing the dynamics of the slow modes. The effective temperature is closely related to the vortex liquid-vortex glass crossover temperature. Interestingly enough, our study demonstrates that the glassy dynamics in the vortex glass is basically identical to the one of a single elastic line in a disordered environment (with the same type of scaling though with different parameters). Possible extensions and the experimental relevance of these results are also discussed.
Redouane Bouhennache - One of the best experts on this subject based on the ideXlab platform.
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Truly Hypercomplex Numbers: Unification of Numbers and Vectors
arXiv: General Mathematics, 2014Co-Authors: Redouane BouhennacheAbstract:Since the beginning of the quest of hypercomplex numbers in the late eighteenth century, many hypercomplex number systems have been proposed but none of them succeeded in extending the concept of complex numbers to higher dimensions. This paper provides a definitive solution to this problem by defining the truly hypercomplex numbers of dimension N greater than or equal to 3. The secret lies in the definition of the Multiplicative Law and its properties. This Law is based on spherical and hyperspherical coordinates. These numbers which I call spherical and hyperspherical hypercomplex numbers define Abelian groups over addition and multiplication. Nevertheless, the Multiplicative Law generally does not distribute over addition, thus the set of these numbers equipped with addition and multiplication does not form a mathematical field. However, such numbers are expected to have a tremendous utility in mathematics and in science in general.
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SPHERICAL AND HYPERSPHERICAL HYPERCOMPLEX NUMBERS MERGING NUMBERS AND VECTORS INTO JUST ONE MATHEMATICAL ENTITY
viXra, 2014Co-Authors: Redouane BouhennacheAbstract:Since the beginning of the quest of hypercomplex numbers in the late eighteenth century, many hypercomplex number systems have been proposed but none of them succeeded in extending the concept of complex numbers to higher dimensions. This paper provides a definitive solution to this problem by defining the truly hypercomplex numbers of dimension N ≥ 3. The secret lies in the definition of the Multiplicative Law and its properties. This Law is based on spherical and hyperspherical coordinates. These numbers which I call spherical and hyperspherical hypercomplex numbers define Abelian groups over addition and multiplication. Nevertheless, the Multiplicative Law generally does not distribute over addition, thus the set of these numbers equipped with addition and multiplication does not form a mathematical field. However, such numbers are expected to have a tremendous utility in mathematics and in science in general.
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SPHERICAL AND HYPERSPHERICAL HYPERCOMPLEX NUMBERS MERGING NUMBERS AND VECTORS INTO JUST ONE MATHEMATICAL ENTITY GENERALIZATION OF COMPLEX NUMBERS TO HIGHER DIMENSIONS
2014Co-Authors: Redouane BouhennacheAbstract:Since the beginning of the quest of hypercomplex numbers in the late eighteenth century, many hypercomplex number systems have been proposed but none of them succeeded in extending the concept of complex numbers to higher dimensions. This paper provides a definitive solution to this problem by defining the truly hypercomplex numbers of dimension N ≥ 3. The secret lies in the definition of the Multiplicative Law and its properties. This Law is based on spherical and hyperspherical coordinates. These numbers which I call spherical and hyperspherical hypercomplex numbers define Abelian groups over addition and multiplication. Nevertheless, the Multiplicative Law generally does not distribute over addition, thus the set of these numbers equipped with addition and multiplication does not form a mathematical field. However, such numbers are expected to have a tremendous utility in mathematics and in science in general.
Yves Louet - One of the best experts on this subject based on the ideXlab platform.
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ICNC - On the performance of joint channel estimation and PAPR reduction scheme
2012 International Conference on Computing Networking and Communications (ICNC), 2012Co-Authors: Youssef Nasser, J.-f. Helard, Yves LouetAbstract:In this paper, we address the performance of joint Peak-to-Average Power Ratio (PAPR) reduction and channel estimation schemes. The target of this work is multifold. First, we propose a novel PAPR reduction scheme for Orthogonal Frequency Division Multiplexing (OFDM) systems: instead of using dedicated pilots for PAPR reduction as with Tone Reservation (TR) method existing in the literature, we propose to use the reserved channel estimation pilots. In this way, we avoid the use of reserved tones and we improve the spectral efficiency. Second, in order to allow their recovery at the receiver, we investigate a Multiplicative Law to be applied on the transmitted pilots. This Law will permit a blind detection at the receiver and avoid sending side information. Third, using the new DVB-T2 standard parameters, the performance of the proposed technique is analyzed and compared with other techniques. We show that the proposed technique is efficient in terms of PAPR reduction value and of spectral efficiency while the channel estimation performance is maintained.
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PAPR reduction approach based on channel estimation pilots for future broadcasting systems
International Journal of Digital Multimedia Broadcasting, 2011Co-Authors: J.-f. Helard, Youssef, Joseph Nasser, Yves LouetAbstract:In this paper, a novel peak-to-average power ratio (PAPR) reduction technique for orthogonal frequency division multiplexing (OFDM) systems is addressed. Instead of using dedicated pilots for PAPR reduction as with the Tone Reservation (TR) method selected by the DVB-T2 standard, we propose to use existing pilots used for channel estimation. In this way, we avoid the use of reserved tone pilots and then, improve the spectral efficiency of the system. In order to allow their recovery at the receiver, these pilots have to follow particular Laws which permit their blind detection and avoid sending side information. In this work, we propose and investigate a Multiplicative Law operating in discrete domain. The operation in time domain aims in reducing degradation due to detection and estimation error in continuous domain. Simulation results are performed using the new DVB-T2 standard parameters. Its performance is compared to the DVB-T2 PAPR Gradient algorithm and to the second order cone programming (SOCP) competitive technique proposed in the literature. We show that the proposed technique is efficient in terms of PAPR reduction value and of spectral efficiency while the channel estimation performance is maintained.
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PAPR reduction approach based on channel estimation pilots for next generations broadcasting systems
International Journal of Digital Multimedia Broadcasting, 2011Co-Authors: Youssef Nasser, Ho A.-t., Helard J.-f., Yves LouetAbstract:In this paper, a novel peak-to-average power ratio (PAPR) reduction technique for orthogonal frequency division multiplexing (OFDM) systems is addressed. Instead of using dedicated pilots for PAPR reduction as with the Tone Reservation (TR) method selected by the DVB-T2 standard, we propose to use existing pilots used for channel estimation. In this way, we avoid the use of reserved tone pilots and then, improve the spectral efficiency of the system. In order to allow their recovery at the receiver, these pilots have to follow particular Laws which permit their blind detection and avoid sending side information. In this work, we propose and investigate a Multiplicative Law operating in discrete domain. The operation in time domain aims in reducing degradation due to detection and estimation error in continuous domain. Simulation results are performed using the new DVB-T2 standard parameters. Its performance is compared to the DVB-T2 PAPR Gradient algorithm and to the second order cone programming (SOCP) competitive technique proposed in the literature. We show that the proposed technique is efficient in terms of PAPR reduction value and of spectral efficiency while the channel estimation performance is maintained.
