# Past seminars

* 1 Feb 2018 16:00 * **Luca Visinelli, ** *Axions in cosmology and astrophysics*

*12 Feb 2018 14:00 * **Roberto Oliveri, ** *Gravitational multipole moments from Noether charges*

* 30 Jan 2018 14:00 * **Eleonora Villa, ** *Theoretical systematics in galaxy clustering in LCDM and beyond*

* 23 Jan 2018 14:00 * **Petr Satunin, ** *Constraints on violation of Lorentz invariance from atmospheric showers initiated by multi-TeV photons*

* 12 Dec 2017 14:00 * ** David Svoboda, ** *Twisted brackets, fluxes, and deformations of para-Kahler manifolds*

* 11 Dec 2017 16:00 * ** Martin Roček, ** *WZW models and generalized geometry*

* 05 Dec 2017 14:00 * ** Dimitris Skliros, ** *Coherent states in String Theory*

* 04 Dec 2017 14:00 * ** Ed Copeland, ** *Screening mechanisms and testing for them in cosmology and the laboratory*

* 30 Nov 2017 14:00 * ** Marc Gillioz, ** *Sum Rules for the "c" Anomaly in 4 Dimensions*

* 28 Nov 2017 14:00 * ** Sugumi Kanno, ** *Decoherence of Bubble Universes*

*27 Nov 2017 14:00 * ** Rachel Houtz, ** *Little Conformal Symmetry and Neutral Naturalness*

08 Nov 2017 14:00 ** Pierre Fleury, ** *Weak lensing with finite beams*

07 Nov 2017 14:00 ** Frederik Lauf, ** *Classification of three-dimensional Chern-Simons-matter theories *

06 Nov 2017 14:00 ** Andrei Gruzinov, ** *Particle production by real (astrophysical) black holes*

23 Oct 2017 14:00 ** George Pappas, ** *Neutron stars as matter and gravity laboratories*

16 Oct 2017 14:00 ** Tessa Baker, ** *Tests of Beyond-Einstein Gravity*

02 Oct 2017 14:00 **Piotr Surowka** *New developments in hydrodynamics*

08 Sep 2017 14:00 **Dani Figueroa**,* Higgs Cosmology: implications of the Higgs for the early Universe*

06 Sep 2017 14:00 **Sergey Ketov***, Starobinsky inflation in supergravity*06 Sep 2017 11:00

**Dalimil Mazáč**

*, Analytic conformal bootstrap and QFT in AdS2*

29 Jun 2017 14:00

**Bruce Bassett**,

*Rise of the Machine: AI and Fundamental Science*

28 Jun 2017 14:00

**Dmitri Semikoz**,

*Signatures of a two million year old nearby supernova in antimatter data*

2 Jun 2017 14:00

**David Alonso**,

*Science with future ground-based CMB experiments*

22 May 2017 14:00

**Mathieu Langer**,

*Magnetizing the intergalactic medium during reionization*16 May 2017 16:00

**Sergey Sibiryakov**,

*Counts-in-cells statistics of cosmic structure*

25 Apr 2017 14:00

**Ippocratis Saltas**,

*What can unimodular gravity teach us about the cosmological constant?*

12 Apr 2017 14:00

**Andrei Nomerotski**,

*Status and Plans for Large Synoptic Survey Telescope*6 Apr 2017 14:00

**Alex Vikman**,

*The Phantom of the Cosmological Time-Crystals**3 Apr 2017 14:00*

**J**

**nan Maharana**

*,**Scattering of Stringy States and T-duality*27 Mar 2017 14:00

**Michal Bilek**,

*Galaxy interactions in MOdified Newtonian Dynamics (MOND)*27 Feb 2017 16:00

**Misao Sasaki,**

*Signatures from inflationary massive gravity*23 Feb 2017 14:00

**Misao Sasaki,**

*Inflation and Beyond*

14 Dec 2016 14:00

**Giovanni Acquaviva**,

*Dark matter perturbations with causal bulk viscosity*9 Dec 2016 14:00

**David Pirtskhalava**,

*Relaxing the Cosmological Constant*14 Nov 2016 14:00

**Glenn Barnich,**

*Finite BMS transformations*

18 Oct 2016 14:00

**Eugeny Babichev,**

*Gravitational origin of dark matter*

**11/12/2017 --**

**(SUNY, Stony Brook)****Martin Roček**Time: 16:00

Place: auditorium

*WZW models and generalized geometry*

**8/11/2017 --**

**(University of Geneva)****Pierre Fleury**Time: 14:00

Place: 117

*Weak lensing with finite beams*

**6/11/2017 --**

**(New York University)****Andrei Gruzinov**Time: 14:00

Place: 226

*Particle production by real (astrophysical) black holes*

**23/10/2017 --**

**(Lisbon Centre for Astrophysics)****George Pappas**Time: 14:00

Place: 226

*Neutron stars as matter and gravity laboratories*

**16/10/2017 --**

**(Oxford University)****Tessa Baker**Time: 14:00

Place: 226

*Tests of Beyond-Einstein Gravity*

**8/9/2017 --**

**(CERN)****Dani Figueroa**Time: 14:00

Place: 117

*Higgs Cosmology: implications of the Higgs for the early Universe.*

**6/9/2017 --**

**(Tokyo Metropolitan University)****Sergey Ketov**Time: 14:00

Place: 117

**Starobinsky inflation in supergravity **

I begin with an introduction to Starobinsky inflation based on (R+R^2) gravity, in light of Planck data about CMB. Next, I introduce the supergravity extensions of Starobinsky inflation, review their problems and possible solutions. I conclude with a discussion of reheating after Starobinsky inflation in the context of supergravity.

**29/6/2017 -- Bruce**

**Bassett**(University of Cape Town)Time: 14:00

Place: Room 117

**Rise of the Machine: AI and Fundamental Science**

**28/6/2017 -- Dmitry**

**Semikoz**(APC, Paris)Time: 14:00

Place: Lecture hall

*Signatures of a two million year old nearby supernova in antimatter data.*

**2/6/2017 --**

**David Alonso**(University of Oxford)Time: 14:00

Place: Room 117

*Science with future ground-based CMB experiments.*

**22/5/2017 --**

**Mathieu Langer**(Université Paris-Sud)Time: 14:00

Place: Room 117

*Magnetizing the intergalactic medium during reionization.*

*An increasing amount of evidence indicates that cosmological sheets, filaments and voids may be substantially magnetised. The origin of magnetic fields in the the Intergalactic Medium is currently uncertain. It seems now well known that non-standard extensions to the physics of the Standard Model are capable of providing mechanisms susceptible of magnetising the Universe at large. Much less well known is the fact that standard, classical physics of matter-radiation interactions possesses actually the same potential. After reviewing briefly our current knowledge about magnetic fields on the largest scales, I will discuss a magnetogenesis mechanism based on the exchange of momentum between hard photons and electrons in an inhomogeneous Intergalactic Medium. Operating in the neighbourhood of ionising sources during the Epoch of Reionization, this mechanism is capable of generating magnetic seeds of relevant strengths on scales comparable to the distance between ionising sources. In addition, summing up the contributions of all ionising sources and taking into account the distribution of gas inhomogeneities, I will show that this mechanism leaves the IGM, at the end of Reionization, with a level of magnetization that might account for the current magnetic fields strengths in the cosmic web.--based on Durrive & Langer, MNRAS, 2015, and Durrive et al. MNRAS 2017 (submitted)--*

**16/5/2017 --**

**Sergey Sibiryakov**(CERN, EPFL, INR RAS)Time: 16:00

Place: Room 117

*Counts-in-cells statistics of cosmic structure and non-perturbative methods of quantum field theory*

**25/4/2017 --**

**Ippocratis Saltas**(University of Lisbon)Time: 11:00

Place: Room 117

*What can unimodular gravity teach us about the cosmological constant?*

**12/4/2017 -- Andrei Nomerotski (Brookhaven National Lab, USA)**

Time: 14:00

Place: Lecture Theatre

*Status and Plans for Large Synoptic Survey Telescope*

Investigation of Dark Energy remains one of the most compelling tasks for modern cosmology. It can be studied with several probes which are accessible through precise and deep surveys of the Universe. In the talk I will review the status and plans for Large Synoptic Survey Telescope, which will precisely measure the positions and shapes of billions of galaxies along with estimates of their distances, providing an order-of-magnitude improvement relative to current experiments. LSST Camera employs thick, fully depleted CCDs with extended infrared sensitivity. The talk will provide more detail on the camera design and will discuss limitations on the achievable precision coming from the instrumentation.

**6/4/2017 -- Alex Vikman**

**(CEICO, Institute of Physics)**Time: 14:00

Place: Lecture Theatre

**The Phantom of the Cosmological Time-Crystals**

I will discuss a recently proposed new cosmological phase where a scalar field moves exactly periodically in an expanding spatially-flat Friedmann universe. On average this phase has a vacuum or de Sitter equation of state and can be interesting to model Inflation and Dark Energy in a novel way. This phase corresponds to a limiting cycle of the equations of motion and can be considered as a cosmological realization of a general idea of a "time-crystal" introduced by Wilczek et. all in 2012. Recently we showed that this cosmological phase is only possible, provided the Null Energy Condition is violated and the so-called Phantom divide is crossed. Using methods from the dynamical systems, we proved that in a rather general class of single scalar field models called k-essence: i) this crossing causes infinite growth of quantum perturbations on short length-scales, and ii) exactly periodic solutions are only possible, provided the limiting cycle encircles a singularity in the phase plane. The configurations neighboring this singular curve in the phase space are linearly unstable on one side of the curve and superluminal on the other side. Moreover, the increment of the instability is infinitely growing for each mode by approaching the singularity, while for the configurations on the other side, the sound speed is growing without limit. We illustrated our general results by analytical and numerical studies of particular models proposed by Wilczek and collaborators. Finally I will briefly discuss systems where this idea of time-crystals may be realized.

**3/4/2017 -- Jnan Maharana (Institute of Physics, Sachivalaya Marg, India)**

Time: 14:00

Place: Room 226.

*Scattering of Stringy States and T-duality*

First a brief overview of target space duality will be presented. Compactification of a closed bosonic string in its massless backgrounds wil be considered when it is compactified on a d-dimensional torus. The vertex operators associated with the moduli of the compactified closed string will be constructed. The Kawai-Llewellyn-Tye factorization technique will be utilized to show the T-duality transformation properties of S-matrix for the moduli.

**27/3/2017 -- Michal Bilek (Astronomical Institute of the Czech Academy of Sciences)**

Time: 14:00

Place: Room 117.

**Galaxy interactions in***MOdified Newtonian Dynamics (MOND)*

**27/2/2017 -- Misao Sasaki**

**(Yukawa Institute for Theoretical Physics, Kyoto -- director)**Time: 16:00

Place: Room 117.

**Signatures from inflationary massive gravity.**

Inflation is a natural platform for modified gravity. In this talk, we consider

a theory that spontaneously violates the local SO(3) symmetry, which gives

rise to a preferred spatial frame during inflation.

As a result, the tensor modes become massive. We argue that this theory

leads to several interesting observational signatures.

**23/2/2017 --**

**Misao Sasaki**

Time: 14:00

Place: Lecture hall.**Colloquium: Inflation and Beyond.**

There is strong observational evidence now that the Universe has

experienced an almost exponential expansion at its very early stage, called

inflation. In this talk I first review the inflationary universe and its observational

predictions. Then I discuss possible future directions beyond and behind theory

of inflation, and their observational signatures.

**14/12/2016 --**

**Giovanni Acquaviva (Charles University, Prague)**

Time: 14:00

**Dark matter perturbations with causal bulk viscosity**We analyse the evolution of perturbations of cold dark matter endowed with bulk viscosity. Focusing on structure formation well within the Hubble radius, the perturbative analysis is carried out in the Newtonian approximation while the bulk viscosity is described by Israel-Stewart's causal theory of dissipation. Differently from previous analysis based on non-causal theories, we obtain a density contrast evolution governed by a third order equation. This framework can be employed to address some of the current inconsistencies in the observed clustering of galaxies.

**9/12/2016 --**

**David Pirtskhalava**(EPFL, Lausanne, Switzerland)

*Relaxing the Cosmological Constant***14/11/2016 --**

**Glenn Barnich**(Université Libre de Bruxelles & International Solvay Institutes)

*Finite BMS transformations***18/10/2016 --**

**Eugeny Babichev**(Laboratoire de Physique Théorique d'Orsay, Orsay, France)

*Gravitational origin of dark matter*