The SEMPARIS seminar webserver hosts annoucements of all seminars taking place in Paris area, in all topics of physics, mathematics and computer science. It allows registered users to receive a selection of announcements by email on a daily or weekly basis, and offers the possibility to archive PDF or Powerpoint files, making it available to the scientific community. [ More information ]
Upcoming Seminars at LPTHE  
[ scheduler view ] 
Wednesday 22 November 2017, 11:00 at LPTHE, Bibliotheque du LPTHE, tour 1314, 4eme etage  SEMEXCEP (Séminaire exceptionel)  condmat 



Abstract:  For the past 30 years, the transport properties in the unusual metallic phase seen in the cuprate superconductors and many other quantum critical metals, have defied an explanation in terms of the standard building blocks of modern physics  particles with local interactions and conservation laws. A recent proposal suggests that all of the properties of such `strange metals' can be understood if the current has an anomalous dimension not determined simply by dimensional analysis. My talk will focus on trying to understand this claim. To demystify this claim, I will first show that even in the standard formulation of gauge theories, there is a loophole in Noether's theorems which has remained `almost' (Noether was aware of it) unnoticed until now, that can allow, in principle, for the current to have any allowable dimension. The only quantum theories to date which exhibit such odd behaviour are bulk diatonic models. The corresponding boundary theory is inherently nonlocal as dictated by the only possible exception to Noether's theorms. The existence of currents having anomalous dimensions, a direct probe of the existence of extra `hidden' dimensions, can be tested with the AharonovBohm effect. I will describe this effect and its potential impact for unlocking the secret of the strange metal in the cuprates. I will also construct the Virasoro algebra for such fractional currents and discuss the general implications for the bulkboundary construction in holography. 
Thursday 23 November 2017, 11:00 at LPTHE, bibliothèque  SEMDARBOUX (Séminaire Darboux  physique théorique et mathématiques)  hepthmathmath.MP 



Abstract:  The main goal of the talk is to give an introduction to tropical geometry making an emphasis on the tropical approach to enumeration of algebraic curves in the plane. This approach, based on Grigory Mikhalkin's correspondence theorem, reduces many enumerative problems of GromovWitten type (complex or real) to a count of certain rectilinear graphs that are called tropical curves. We discuss enumeration of tropical curves with different multiplicities, in particular, with the polynomial multiplicities proposed recently by Florian Block and Lothar Göttsche; the enumeration with the help of these multiplicities can be interpreted as quantization of the number of complex solutions in the enumerative problems under consideration. 
Friday 24 November 2017, 14:00 at LPTHE, Library  LPTHEPPH (Particle Physics at LPTHE)  hepph 



Abstract:  The possibility that the Higgs boson is a composite state of an underlying confining dynamics is still open. After a brief recap of the main features and properties of this class of models, I will discuss the reasons why we expect the presence of light (pseudo)scalars as a generic prediction of composite Higgs models. Their phenomenology at the LHC will also be touched upon. 
Thursday 30 November 2017, 10:00 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 



Abstract:  Lovelock theories are the most general theories of a metric tensor with second order equations of motion. Horndeski theories are the most general fourdimensional theories of a metric tensor and a scalar field with second order equations of motion. Many hundreds of papers have been written about these theories. But it is unknown whether they satisfy a basic consistency requirement, namely wellposedness of the initial value problem. I will discuss this problem and explain why the method used to establish wellposedness of the Einstein equation fails for Lovelock theories and the most general Horndeski theories. 
Thursday 30 November 2017, 11:45 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 



Abstract:  We will analyse the Regge limit of certain four point functions in CFTs and will argue that holographic CFTs must be described by Einstein gravity. 
Friday 1 December 2017, 14:00 at LPTHE, Library  LPTHEPPH (Particle Physics at LPTHE)  hepph 



Abstract:  There may be a sofarundiscovered neutral, stable particle composed of 6 quarks, denoted S, with mass m_S ~ 2 m_p. If so, the S is an excellent Dark Matter candidate. I will explain why such a particle would not have been detected, propose experiments to discover it, discuss why direct detection experiments to date do not exclude it, mention some of the numerous astrophysical benefits of a DMbaryon interaction, and how it works cosmologically giving the observed DMbaryon abundance ratio and the baryon asymmetry of the Universe. 
Thursday 14 December 2017, 10:00 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 



Abstract:  I will first briefly review the mechanism of bubble nucleation as a possible instability channel for AdS vacua. Secondly I will discuss it in the specific context of effective supergravity models arising from string compactifications truncated to their closed string sector. By making use of positive energy theorems, I will show that such instabilities do not really occur within this setup. Finally, I will discuss the relation between the above analysis and the weak gravity conjecture (WGC) and will eventually argue that some expected universal instabilities for nonsupersymmetric AdS are crucially linked to the coupling between open and closed string sector. 
Thursday 14 December 2017, 11:45 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 


Thursday 11 January 2018, 11:45 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 



Abstract:  We put forward the Axionic String Ansatz (ASA), which provides a unified description for the worldsheet dynamics of confining strings in pure YangMills theory both in $D=3$ and $D=4$ spacetime dimensions. The ASA is motivated by the excitation spectrum of long confining strings, as measured on a lattice, and by recently constructed integrable axionic noncritical string models. According to the ASA, pure gluodynamics in 3D is described by a noncritical bosonic string theory without any extra local worldsheet degrees of freedom. We argue that this assumption fixes the set of quantum numbers (spins, $P$ and $C$parities) of almost all glueball states. We confront the resulting predictions with the properties of approximately $1^2+2^2+3^2+5^2=39$ lightest glueball states measured on a lattice and find a good agreement. 
Thursday 18 January 2018, 11:00 at LPTHE, bibliothèque  SEMDARBOUX (Séminaire Darboux  physique théorique et mathématiques)  mathmath.MP 


Thursday 8 February 2018, 11:00 at LPTHE, bibliothèque  SEMDARBOUX (Séminaire Darboux  physique théorique et mathématiques)  mathmath.MP 


Thursday 15 March 2018, 11:00 at LPTHE, bibliothèque  SEMDARBOUX (Séminaire Darboux  physique théorique et mathématiques)  mathmath.MP 


Thursday 29 March 2018, 11:00 at LPTHE, bibliothèque  SEMDARBOUX (Séminaire Darboux  physique théorique et mathématiques)  mathmath.MP 


Thursday 5 April 2018, 10:00 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 


Thursday 5 April 2018, 11:45 at IHP, 314  RENCTHEO (Rencontres Théoriciennes)  hepth 


Thursday 24 May 2018, 11:00 at LPTHE, bibliothèque  SEMDARBOUX (Séminaire Darboux  physique théorique et mathématiques)  mathmath.MP 



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