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PRODID:-//Seminarios de Física Teorica - ECPv3.12.3//NONSGML v1.0//EN
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X-WR-CALNAME:Seminarios de Física Teorica
X-ORIGINAL-URL:http://jacobi.fis.ucm.es/wordpress
X-WR-CALDESC:Events for Seminarios de Física Teorica
BEGIN:VEVENT
DTSTART:20181126T110000Z
DTEND:20181126T130000Z
DTSTAMP:20181212T170137Z
CREATED:20181123T092453Z
LAST-MODIFIED:20181123T092453Z
UID:209-1543230000-1543237200@jacobi.fis.ucm.es
SUMMARY:Rubén Arjona
DESCRIPTION:Lugar: Seminario de Física Teórica\, planta 2\nDía: Lunes 26 de noviembre\nHora: 15:00\n\nPonente: Rubén Arjona Fernández\nTítulo: Unraveling the effective fluid approach for f(R) models in the sub-horizon approximation.\n\nAbstract: We provide explicit formulae for the effective fluid approach of f(R) theories\, such as the Hu & Sawicki and the designer models. Using the latter and simple modifications to the CLASS code\, which we call EFCLASS\, in conjunction to very accurate analytic approximations for the background evolution\, we obtain competitive results in a much simpler and less error-prone approach. We also\nderive the initial conditions in matter domination and we find they differ from those already found in the literature for a constant w model. We then use the aforementioned models to derive constraints from the latest cosmological data\, including supernovae\, BAO\, CMB\, H(z) and growth-rate data\, and we find they are statistically consistent to the LCDM model. Finally\, we find that the viscosity parameter in realistic models is not constant as commonly assumed\, but\nrather evolves significantly over several orders of magnitude\, something which could affect forecasts of upcoming surveys.\n\n-----------------------------------------------------------------------------------------------------------------------\n\nMuchas gracias y un saludo
URL:http://jacobi.fis.ucm.es/wordpress/seminario/ruben-arjona/
LOCATION:Avenida Complutense\, Madrid\, Madrid\, 28040\, España
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BEGIN:VEVENT
DTSTART:20181129T103000Z
DTEND:20181129T120000Z
DTSTAMP:20181212T170137Z
CREATED:20181113T105550Z
LAST-MODIFIED:20181113T105550Z
UID:203-1543487400-1543492800@jacobi.fis.ucm.es
SUMMARY:Ignacio Luengo
DESCRIPTION:Fecha y hora: Jueves 29 de noviembre 14:30\nLugar: Seminario de Física Teórica 3º planta\n\nPonente: Ignacio Luengo\, Facultad de Matemáticas\, UCM\n\n \n\nTitle: Post-quantum cryptography with polynomials.\n\nAbstract:Post-quantum cryptography is the public-key cryptography resistant to future quantum computers. In this talk we will talk about a post-quantum cryptosystem called DME (Double Matrix Exponentiation) based on multivariate polynomial applications that we have developed (using ideas of Algebraic Geometry)\, patented and present it to the NIST contest to choose the future post-quantum cryptography standard (https://csrc.nist.gov/Projects/Post-Quantum-Cryptography/Round-1-Submissions).\nWe will also present the questions and problems of Conmutative Algebra related with the algebraic cryptoanalysis of the scheme DME.\nThe preprint can be found in the web above and in\nhttp://www.mat.ucm.es/~iluengo/DME
URL:http://jacobi.fis.ucm.es/wordpress/seminario/ignacio-luengo/
LOCATION:Avenida Complutense\, Madrid\, Madrid\, 28011\, España
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BEGIN:VEVENT
DTSTART:20181204T103000Z
DTEND:20181204T120000Z
DTSTAMP:20181212T170137Z
CREATED:20181121T120650Z
LAST-MODIFIED:20181121T120650Z
UID:205-1543919400-1543924800@jacobi.fis.ucm.es
SUMMARY:Adrián Feiguin
DESCRIPTION:Fecha y hora: Martes 4 de diciembre\, 14:30\n\nLugar: Seminario 3ª planta\n\nPonente: Adrian E. Feiguin\, Northeastern University\, Boston\, USA\n\nTítulo:The spectral function of Mott-insulating Hubbard ladders: From fractional excitations to coherent quasi-particles\n\nAbstract:When electrons are confined in one spatial dimension\, they may loose their identity as individual particles\, and ``split'' into separate excitations carrying spin (a spinon)\, and charge (a holon) and\, as a consequence\, Landau's quasi-particle picture breaks down. Whether spin-charge separation survives in dimensions greater than d=1 has been a topic of great debate\, particularly in the context of high-temperature superconductivity. A peculiar case that can shed some light on this problem consists of coupling two half-filled Hubbard chains into a ladder geometry. When the Mott insulator is doped\, it is expected that polaronic quasiparticles (a bound state of a spinon and a holon) will form\, restoring Landau's paradigm. We study the spectral function of two-leg Mott insulating Hubbard ladders using the time-dependent density matrix renormalization group method (tDMRG). The high-resolution spectrum displays features of spin-charge separation and a scattering continuum of excitations with coherent bands of bound states ``leaking'' from it. As the inter-leg hopping is increased\, the continuum in the bonding channel moves to higher energies and spinon and holon branches merge into a single coherent quasi-particle band. Simultaneously\, the spectrum undergoes a crossover from a regime with two minima at incommensurate values of momentum (a Mott insulator)\, to one with a single minimum at k_x=pi (a band insulator). We identify the presence of a continuum of scattering states consisting of a triplon and a polaron. The sharp edge of the continuum in the anti-bonding sector indicates the formation of bound states with higher spin $S=3/2$\, ferromagnetic ``spin bags'' in which the hole can move freely. We analyze the processes leading to quasiparticle formation by studying the time evolution of charge and spin degrees of freedom in real space after the hole is created. At short times\, incoherent holons and spinons are emitted but after a characteristic time\, charge and spin form polarons that propagate coherently. In addition\, we infer the full spectrum of the 2D Hubbard model in the thermodynamic limit by coupling ladders in the perpendicular direction using cluster perturbation theory. A remarkable advantage of this approach is that unlike small clusters\, the one-dimensional systems are already ``infinite''. Excellent agreement with quantum Monte Carlo and other cluster methods is obtained.
URL:http://jacobi.fis.ucm.es/wordpress/seminario/adrian-feiguin/
LOCATION:Avenida Complutense\, Madrid\, Madrid\, 28011\, España
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BEGIN:VEVENT
DTSTART:20181210T103000Z
DTEND:20181210T120000Z
DTSTAMP:20181212T170137Z
CREATED:20181105T104228Z
LAST-MODIFIED:20181105T104228Z
UID:198-1544437800-1544443200@jacobi.fis.ucm.es
SUMMARY:Juan Margaluf
DESCRIPTION:Fecha y hora: Lunes\, 10 de diciembre 14:30\nLugar: Seminario de Física Teórica 3º planta\n\nPonente: Juan Margaluf\, ICMAT\n\nTítulo: From partitions to Laplace transform. Study of the spectrum of the area operator.\n\nAbstract: The area operator\, that appears in the context of Loop Quantum Gravity\, has as eigenvalues all possible numbers of the form\n\[\sum_{i=1}^n \sqrt{n_i(n_i+2)\] for some natural numbers $n_i$. Several approximate methods have been proposed along the years to study the distribution of these eigenvalues. They rely on approximations to get rid of the square root and known results about integer partitions\, in particular\, the classic asymptotic estimates due to Hardy\, Ramanujan\, and Rademacher. The main problem with these approaches is that different approximations lead to different results and\, hence\, are not conclusive.\n\nIn this talk\, I will present a method that we developed\, based on Laplace transforms\, that provides a very accurate solution to this problem. The representation that we get is valid for any area and can be used\, in particular\, to obtain its asymptotics in the large area limit.
URL:http://jacobi.fis.ucm.es/wordpress/seminario/juan-margaluf/
LOCATION:Avenida Complutense\, Madrid\, Madrid\, 28011\, España
END:VEVENT
BEGIN:VEVENT
DTSTART:20181211T103000Z
DTEND:20181211T120000Z
DTSTAMP:20181212T170137Z
CREATED:20181105T104457Z
LAST-MODIFIED:20181112T090928Z
UID:199-1544524200-1544529600@jacobi.fis.ucm.es
SUMMARY:Manuel Asorey
DESCRIPTION:Fecha y hora: Martes 11 de diciembre 14:30\nLugar: Seminario de Física Teórica 3º planta\n\nPonente: Manuel Asorey\, Universidad de Zaragoza\n\nTítulo: Bulk-Edge dualities in Topological Matter\n\nAbstract: Novel bulk-edge dualities have recently emerged in\ntopological materials from the observation of some\nphenomenological correspondences. The similarity of\nthese dualities with string theory dualities is very\nappealing and has boosted a quite significant number of\ncross field studies. We analyze the bulk-edge dualities\nin some simple planar systems\, where the duality\ncan be scrutinized by powerful analytic techniques.\nIn particular we will discuss the connections with\nAtiyah-Patodi-Singer index theorems.
URL:http://jacobi.fis.ucm.es/wordpress/seminario/manuel-asorey/
LOCATION:Avenida Complutense\, Madrid\, Madrid\, 28011\, España
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