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  
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Tuesday 23 July 2019, 14:00 at LPTHE, library  LPTHEPPH (Particle Physics at LPTHE)  hepph 



Abstract:  Searching for deviations in quartic gauge boson couplings (QGCs) is one of the main goals of the electroweak program at the LHC. We consider positivity bounds adapted to the Standard Model EFT, and show that a set of positivity constraints on 18 anomalous QGC couplings can be derived, by requiring that the vector boson scattering amplitudes satisfy the fundamental principles of quantum field theory. We solve the positivity inequalities and find that the allowed parameter space is carved out by the intersection of pyramids, prisms, and cones. Altogether, the allowed parameter space is reduced to ~2% of total. These bounds provide guidance to future BSM searches and could affect the limits on couplings by modifying the prior. 
Thursday 25 July 2019, 11:00 at IPN, Salle A015  IPNX (Séminaire commun de physique théorique des particules IPNCPHTX)  hepph 



Abstract:  Thanks to its multiTeV LHC proton and lead beams, the LHC complex allows one to perform the most energetic fixedtarget experiments ever and to study with high precision pp and pA collisions at \sqrt(sNN) = 115 GeV and Pbp and PbA collisions at \sqrt(sNN) = 72 GeV. Such an experiment will facilitate a broad physics program, covering the largex frontier for particle and astroparticle physics, spin and heavyion physics. We will present performance studies for measurements of the production of DrellYan pairs, quarkonia, open heavyflavor mesons as well as lightflavor hadrons in pp, pA and PbA collisions using the LHCb and ALICE detectors in a fixedtarget mode. Recent progress on the implementation of the fixed target program at the LHC and its perspectives will be also discussed. 
Friday 26 July 2019, 14:00 at LPTHE, library  LPTHEPPH (Particle Physics at LPTHE)  hepph 



Abstract:  Extensions of the Standard Model often come with additional, possibly electroweakly charged Higgs states, the prototypal example being the TwoHiggsDoublet Model. While collider phenomenology does not exclude the possibility for some of these new scalar fields to be light, it is relatively natural to consider masses in the multiTeV range, where decoupling of the SMlike boson is almost guaranteed. The appearance of a hierarchy between the newphysics states and the electroweak scale then leads to sizable electroweak corrections in e.g. the decays of the heavy Higgs, which are dominated by effects of infrared type, namely Sudakov logarithms. Such radiative contributions obviously affect the twobody decays, but should also be paired with the radiation of electroweak (or lighter Higgs) bosons for a consistent picture at the oneloop order. Resummation of the leading terms is also relatively easy to achieve. We revisit these questions in the specific case of the fermionic decays of heavy Higgs particles in the NexttoMinimal Supersymmetric Standard Model, in particular pointing out the consequences of the threebody final states for the branching ratios of the heavy scalars. 
Tuesday 3 September 2019, 11:00 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTGEN (Séminaire général du SPhT)  physics 



Abstract:  By definition the choreography (dancing curve) is a closed trajectory on which $n$ classical bodies move chasing each other without collisions. The first choreography (the Remarkable Figure Eight) at zero angular momentum was discovered unexpectedly by C Moore (Santa Fe Institute) at 1993 for 3 equal masses in $R^3$ Newtonian gravity numerically. At the moment about 6,000 choreographies in $R^3$ Newtonian gravity are found, all numerically for different $n > 2$. A number of 3body choreographies is known in $R^2$ Newtonian gravity, for LennardJones potential (hence, relevant for molecular physics), and for some other potentials, again numerically; it might be proved their existence for quarkonia potential. \par Does exist (non)Newtonian gravity for which dancing curve is known analytically?  Yes, a single example is known  it is algebraic lemniscate by Jacob Bernoulli (1694)  and it will be a concrete example of the talk. Astonishingly, $R^3$ Newtonian Figure Eight coincides with algebraic lemniscate with $\chi^2$ deviation $\sim 10^{7}$. Both choreographies admit any odd numbers of bodies on them. Both 3body choreographies define maximally superintegrable trajectory with 7 constants of motion. \par Talk will be accompanied by numerous animations. 
Monday 16 September 2019, 10:45 at LPTMC, Jussieu, tower 1312, room 523  SEMLPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)  condmat.meshall 



Abstract:  We identify the persistence probability for the spin located at the origin of a halfspace magnetized GlauberIsing chain as a Fredholm Pfaffian gap probability generating function with a sechkernel. This is then recast as a taufunction for a certain Painlevé VI transcendent  a sort of exact Kramers' formula for the associated explicitely timedependent Hamiltonian  where the persistence exponent emerges as an asymptotic decay rate. By a known yet remarkable correspondence that relates Painlevé equations to Bonnet surfaces, the persistence probability has also a geometric meaning à la GaussBonnet in terms of the intrinsic curvature of the underlying surface. Since the same sechkernel with an underlying Pfaffian structure shows up in a variety of Gaussian firstpassage problems, our Painlevé VI characterization appears as a universal probability distribution akin to the famous Painlevé II TracyWidom laws. Its tail behavior in the magnetizationsymmetric case allows in particular to recover the exact value 3/16 for the persistence exponent of a 2d diffusing random field, as found very recently by Poplavskyi and Schehr (arXiv:1806.11275). Due to its topological origin, this value should constitute the superuniversal persistence exponent for the coarsening of a nonconserved scalar order parameter in two space dimensions. 
Monday 16 September 2019, 14:00 at LPNHE, Amphi Charpak  LPNHE (Séminaires du LPNHE)  hepex 


Monday 23 September 2019, 10:45 at LPTMC, Jussieu, tower 1312, room 523  SEMLPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)  condmat.meshall 


Monday 30 September 2019, 10:45 at LPTMC, Jussieu, tower 1312, room 523  SEMLPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)  condmat.meshall 


Wednesday 2 October 2019, 14:15 at IPHT, Salle Claude Itzykson, Bât. 774  IPHTMAT (Séminaire de matrices, cordes et géométries aléatoires)  hepth 


Tuesday 22 October 2019, 11:30 at LPTENS, LPTENS library  STRLPTENSHE (Séminaire commun LPTENS/LPTHE)  hepth 


Monday 25 November 2019, 10:45 at LPTMC, Jussieu, tower 1312, room 523  SEMLPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)  condmat.meshall 


Monday 9 December 2019, 10:45 at LPTMC, Jussieu, tower 1312, room 523  SEMLPTMC (Séminaire du Laboratoire de Physique Théorique de la Matière Condensée)  condmat.meshall 



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