Pantheon SEMPARIS Le serveur des séminaires parisiens Paris

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
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Wednesday 22 November 2017, 11:00 at LPTHE, Bibliotheque du LPTHE, tour 13-14, 4eme etage SEM-EXCEP (Séminaire exceptionel) cond-mat
Philip Phillips ( University of Illinois ) Anomalous Dimensions for Conserved Currents as a loop-hole in Noether's Theorems
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 loop-hole in Noether's theorems which has remained `almost' (Noether was aware of it) un-noticed 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 non-local 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 Aharonov-Bohm 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 bulk-boundary construction in holography.

Thursday 23 November 2017, 11:00 at LPTHE, bibliothèque SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) hep-th|math|math.MP
Ilia Itenberg ( IMJ-PRG ) Tropical geometry and enumeration of curves
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 Gromov-Witten 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 LPTHE-PPH (Particle Physics at LPTHE) hep-ph
Giacomo Cacciapaglia ( IPNL ) Light (pseudo)scalars in composite Higgs models
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 RENC-THEO (Rencontres Théoriciennes) hep-th
Harvey Reall ( DAMTP, Cambridge, UK ) On the well-posedness of Lovelock and Horndeski theories of gravity
Abstract: Lovelock theories are the most general theories of a metric tensor with second order equations of motion. Horndeski theories are the most general four-dimensional 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 well-posedness of the initial value problem. I will discuss this problem and explain why the method used to establish well-posedness of the Einstein equation fails for Lovelock theories and the most general Horndeski theories.

Thursday 30 November 2017, 11:45 at IHP, 314 RENC-THEO (Rencontres Théoriciennes) hep-th
Manuela Kulaxizi ( Trinity College Dublin ) Einstein gravity from conformal field theory
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 LPTHE-PPH (Particle Physics at LPTHE) hep-ph
Glennys Farrar ( CCPP - NY U. ) Sexaquark Dark Matter
Abstract: There may be a so-far-undiscovered 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 DM-baryon interaction, and how it works cosmologically giving the observed DM-baryon abundance ratio and the baryon asymmetry of the Universe.

Thursday 14 December 2017, 10:00 at IHP, 314 RENC-THEO (Rencontres Théoriciennes) hep-th
Giuseppe Dibitetto ( Uppsala University ) About the (in)stability of stringy AdS vacua
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 non-supersymmetric AdS are crucially linked to the coupling between open and closed string sector.

Thursday 14 December 2017, 11:45 at IHP, 314 RENC-THEO (Rencontres Théoriciennes) hep-th
Michal Spalinski TBA

Thursday 11 January 2018, 11:45 at IHP, 314 RENC-THEO (Rencontres Théoriciennes) hep-th
Sergei Dubovsky ( New York University ) Towards a theory of confining strings
Abstract: We put forward the Axionic String Ansatz (ASA), which provides a unified description for the worldsheet dynamics of confining strings in pure Yang--Mills theory both in $D=3$ and $D=4$ space-time dimensions. The ASA is motivated by the excitation spectrum of long confining strings, as measured on a lattice, and by recently constructed integrable axionic non-critical string models. According to the ASA, pure gluodynamics in 3D is described by a non-critical 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 SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) math|math.MP
David Hernandez ( IMJ-PRG ) TBA

Thursday 8 February 2018, 11:00 at LPTHE, bibliothèque SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) math|math.MP
Emmanuel Letellier ( IMJ-PRG ) TBA

Thursday 15 March 2018, 11:00 at LPTHE, bibliothèque SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) math|math.MP
Oliver Schnetz ( Erlangen ) TBA

Thursday 29 March 2018, 11:00 at LPTHE, bibliothèque SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) math|math.MP
Nicolas Bergeron ( IMG-PRG ) TBA

Thursday 5 April 2018, 10:00 at IHP, 314 RENC-THEO (Rencontres Théoriciennes) hep-th
Oscar Dias ( Southampton ) TBA

Thursday 5 April 2018, 11:45 at IHP, 314 RENC-THEO (Rencontres Théoriciennes) hep-th
James Sparks ( Oxford ) TBA

Thursday 24 May 2018, 11:00 at LPTHE, bibliothèque SEM-DARBOUX (Séminaire Darboux - physique théorique et mathématiques) math|math.MP
Frédéric Chapoton ( Strasbourg ) TBA

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