**Friday, May 24, 2019**

Princeton University Gravity Initiative Lunch

“Static and Dynamical Black Holes in Modified Gravity with Quantum Origin”

Location: Jadwin Hall, Room 102

Time: 12:00 PM

Speaker(s): Aaron Held, Heidleberg University**Description:**Black holes allow a unique probe of spacetime in the strong-curvature regime. With the Event Horizon Telescope capturing humanities first image of a black hole, and the beginning of the era of gravitational-wave astronomy, an unprecedented wealth of data allows testing General Relativity in these most extreme conditions. To do so, it is crucial to have consistent and theoretically well-motivated theories to predict possible deviations. I will discuss theoretical progress in predicting generic modifications expected from quantum gravity. For static black holes, this includes the modified horizon structure and the resulting black-hole shadow. I will explicitly discuss modifications to the shadow shape and size of spinning and non-spinning black holes expected from asymptotically safe quantum gravity. Such effects could be a generic consequence of a larger class of quantum-gravity theories which exert a quantum repulsive force to resolve singularities.Further, I will discuss first results on the dynamics of black holes including higher-order curvature corrections. The latter are generically predicted by many quantum-gravity theories and only very weakly constrained by solar-system observations. I will present first results on a research program to numerically evolve dynamical black-hole spacetimes in quadratic gravity.

**Tuesday, May 28, 2019**

High Energy Theory Seminar

“Holographic Schwinger-Keldysh effective field theories”

Location: Jadwin Hall, PCTS Seminar Room, 4th Floor

Time: 2:00 PM

Speaker(s): Natalia Pinzani-Fokeeva, KU Leuven**Description:**Hydrodynamics has been recently reformulated as an effective field theory based on an underlying Schwinger-Keldysh partition function. After an introduction to the formalism, I will show how effective actions of this type can be derived from holography using a mixed signature bulk spacetime whereby an eternal asymptotically anti-de Sitter black hole is glued to its Euclidean counterpart along an initial time slice in a way to match the desired double-time contour of the dual field theory. For concreteness, I will consider the example of dissipative low-energy dynamics of relativistic charged matter at strong coupling in a fixed thermal background.

**Tuesday, June 4, 2019**

Gordon & Betty Moore Foundation Seminar

“Challenging the Pauli Exclusion Principle by Hunting “Impossible” Atoms in the Cosmic Silence”

Location: Bloomberg Lecture Hall

Time: 2:00 PM

Speaker(s): Dr. Catalina Oana Curceanu, Senior Researcher, Frascati National Laboratory of the INFN (Italy)**Description:**We are experimentally investigating possible violations of the Pauli Exclusion Principle in the cosmic silence of the Gran Sasso underground laboratory in Italy, by hunting "impossible" atomic transitions. I shall present our recent results and method to hunt for small violations of the Pauli Exclusion Principle (PEP) for electrons through the search for PEP "prohibited" X-ray transitions in copper and lead targets within the VIP2 experiment, and discuss possible implications for theories beyond the Standard Model and our future plans.

**Wednesday, June 5, 2019**

Physics Group Meeting

“Geometric Extremization for Supersymmetric $AdS_3$ and $AdS_2$ Solutions”

Location: Bloomberg Lecture Hall

Time: 1:45 PM

Speaker(s): Jerome Gauntlett, Imperial College London**Description:**We consider supersymmetric $AdS_3\times Y_7$ solutions of type IIB supergravity dual to N=(0,2) SCFTs in d=2, as well as $AdS_2\times Y_9$ solutions of D=11 supergravity dual to N=2 supersymmetric quantum mechanics, some of which arise as the near horizon limit of supersymmetric, charged black hole solutions in $AdS_4$. The geometry underlying these solutions was first identified in 2005-2007. Around that time infinite classes of explicit supergravity solutions were also found but, surprisingly, there was little progress in identifying the dual SCFTs.We will discuss new results concerning the $Y_{2n+1}$ geometries that provide significant new insights. For the case of $Y_7$, there is a novel variation principle that allows one to calculate the central charge of the dual SCFT without knowing the explicit metric. This provides a geometric dual of c-extremization for d=2 N=(0,2) SCFTs analogous to the well known geometric duals of a-maximization of d=4 N=1 SCFTs and F-extremization of d=3 N=2 SCFTs in the context of Sasaki-Einstein geometry. In the case of $Y_9$ the variational principle can also be used to obtain properties of the dual N=2 quantum mechanics as well as the entropy of a class of supersymmetric black holes in $AdS_4$ thus providing a geometric dual of $I$-extremization.

We have also developed some powerful new tools based on a novel kind of toric geometry, which lead to additional insights as well as the prospect of making further significant progress in this area.

**Friday, June 7, 2019**

Gordon & Betty Moore Foundation Seminar

“Testing Collapse Models Underground by Searching the Spontaneous Radiation (How to go from “to be AND not to be” to “to be OR not to be”)”

Location: Bloomberg Lecture Hall

Time: 1:45 PM

Speaker(s): Dr. Catalina Oana Curceanu, Senior Researcher, Frascati National Laboratory of the INFN (Italy)**Description:**We are experimentally investigating possible violations of standard quantum mechanics predictions in the Gran Sasso underground laboratory in Italy. In particular, we are testing the collapse models, proposed as a solution of the measurement problem (Schroedinger cat paradox), by chasing the spontaneous radiation predicted by these models in the cosmic silence. I shall present our recent results on hunting this spontaneously emitted radiation, which set very stringent limits on models parameters. I shall also discuss the implications of our results and future plans.

**Thursday, June 13, 2019**

Gordon & Betty Moore Foundation Seminar

“The Schroedinger Cat Meets the Neutron Stars: From Exotic Atoms Studies to Impossible Atoms Hunting”

Location: Jadwin Hall, Room 303

Time: 2:00 PM

Speaker(s): Dr. Catalina Oana Curceanu, Senior Researcher, Frascati National Laboratory of the INFN (Italy)**Description:**I shall present a series of frontier experiments searching for X rays coming from exotic atoms produced at the DAFNE collider of LNF-INFN (Italy) and from processes violating Quantum Mechanics predictions at the Italian Gran Sasso underground laboratory. In the first part of the talk I shall introduce the studies of kaonic atoms in the framework of the SIDDHARTA collaboration at the DAFNE Collider at the LNF-INFN, Frascati (Roma) laboratory. Combining the excellent quality kaon beam delivered by the DAFNE collider with new experimental techniques, as fast and very precise X ray detectors, like the Silicon Drift Detectors, we have performed unprecedented measurements on kaonic hydrogen and helium. Presently, a major upgrade of the setup, SIDDHARTA-2 is being realized to perform in the coming year the first ever measurement of kaonic deuterium. Kaonic atoms studies represent an opportunity to unlock the secrets of the strong interaction in the strangeness sector and understand the role of strangeness in the Universe, from nuclei to the stars. In the second part of the talk I shall present the VIP experiment at the LNGS underground laboratory searching for impossible atoms, i.e. atoms prohibited by the Pauli Exclusion principle, which might exist in some theories beyond the Standard Model. Also, I shall briefly discuss the search of the so-called spontaneous radiation linked with collapse models dealing with the measurement problem (Schroedinger cat paradox) and the interplay with gravity.