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September 8th 2025: Azadeh Maleknejad (Swansea, UK), 'Matter Creation by Cosmic Perturbations at 1-loop'.
October 6th 2025: Daniel Sudarsky (ICN, Mexico), TBA
November 3rd 2025: Jennie Traschen (Amherst, USA), TBA
December 1st 2025: Panel discussion on black hole information paradox
February 3rd 2025: Nicola Pinamonti (Genoa, Italy), 'Semiclassical Einstein equations. Theoretical aspects and some applications'.
March 3rd 2025: Erik Curiel (Bonn, Germany), 'Semi-Classical Gravity as Effective Field Theory and the Information-Loss Paradox'.
March 31st 2025: Silvia Pla (TUM, Germany), 'Low-energy states and CPT-invariance at the big bang '.
May 12th 2025: Christiane Klein (York, UK), 'The challenges of exploring quantum fields in rotating black holes'.
Speaker: Azadeh Maleknejad
Title: Matter Creation by Cosmic Perturbations at 1-loop
Abstract: Conformal fields cannot be produced purely gravitationally in an expanding universe (4d FLRW geometry) at the tree level. However, this picture changes at the gravitational 1-loop level in the presence of cosmic perturbations, leading to a new and unavoidable mechanism for gravitational particle production. In this talk, I will explore the theory and cosmological implications of this effect.
Speaker: Christiane Klein
Title: The challenges of exploring quantum fields in rotating black holes
Abstract: In an era where the black holes in the universe become observationally accessible, it is increasingly important to have a good theoretical understanding of these objects. Since astrophysical black holes are usually rotating, this is the class of black holes one would like to understand, not only within the framework of GR, but also in extended frameworks such as semiclassical gravity. In this talk, I will discuss different features of rotating black holes and the challenges and opportunities they present for the study of free quantum theories on these spacetimes.
Speaker: Silvia Pla
Title: Low-energy states and CPT-invariance at the big bang
Abstract: In this talk, I will explain how to construct CPT-invariant quantum states in a radiation dominated-universe for scalars and spin ½ fields. I will show the explicit boundary conditions that these states must satisfy to become ultraviolet regular [Hadamard] and discuss the phenomenological consequences of the different choices (e.g., the impact on the predicted mass of a heavy right-handed neutrino). I will also discuss the motivation of this analysis and the role of the conformal anomaly (or the absence of it).
Speaker: Erik Curiel
Title: Semi-Classical Gravity as Effective Field Theory and the Information-Loss Paradox
Abstract: I examine several different formulations of the Information-Loss Paradox, discussing how they may and may not be related to each other. I then discuss what bearing a resolution of any of the formulations could have on attempts to formulate a theory of quantum gravity, in light of the fact that the framework of semi-classical gravity, in which the paradox is derived, is manifestly an effective field theory. I discuss two different ways one might treat semi-classical gravity as an effective field theory, and analyze the different possible consequences for each on the paradox. I conclude that the paradox is not necessarily problematic, though for reasons quite different from those of physicists such as Unruh and Wald and philosophers such as Maudlin, who come to a similar conclusion.
Speaker: Nicola Pinamonti
Title: Semiclassical Einstein equations. Theoretical aspects and some applications
Abstract: In this talk, we discuss properties of the semiclassical Einstein equation, which describes the backreaction of quantum matter on the geometry of classical backgrounds. After outlining general features of the equation and its solutions, we focus on backgrounds representing cosmological spacetimes. The matter is modeled as a quantum scalar field with a generic mass and arbitrary coupling to scalar curvature. We observe that the expectation value of the matter stress tensor, which sources gravity, contains a nonlocal term with higher-order derivatives. This term complicates a direct analysis of the solution of the system. We show how to address this issue by reformulating the semiclassical equation into a form suitable for analysis with Banach fixed-point methods.