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Jun'ichi Yokoyama28/09/2026, 09:30
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Ryo Namba28/09/2026, 11:00
Perturbations around a non-trivial spacetime background encode much of the physics we can extract from it --- the ringdown spectrum of a perturbed black hole, or particles produced in a cosmological background. In both cases the relevant mode equation is treated in the WKB approximation, whose solutions are used to impose boundary conditions on the asymptotic states that fix the...
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Yuko Urakawa28/09/2026, 11:50
Infrared divergences in inflationary correlators raise the question of what is observable during inflation. We formulate a locality condition on how the soft modes are attached to the hard sector — patch by patch on a super-horizon lattice — and show that it ensures the infrared regularity of inflationary perturbations, the soft theorems for the correlation functions, and the suppression of...
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Misao Sasaki28/09/2026, 14:10
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Shinji Mukohyama29/09/2026, 09:30
Hořava-Lifshitz gravity is a candidate theory of quantum gravity characterized by anisotropic scaling between space and time and improved ultraviolet behavior. In this talk, I will first review the basic ideas of the theory, its current status, and its implications for cosmology. I will then discuss recent developments in quantum cosmology based on Hořava-Lifshitz gravity, highlighting novel...
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Kristina Giesel29/09/2026, 11:00
In loop quantum cosmology (LQC), the classical big bang singularity is replaced by a quantum bounce. This raises the possibility that pre-inflationary quantum gravity effects could leave observable imprints on primordial cosmological perturbations. However, extracting such signatures requires assumptions about the evolution of perturbations through the high curvature regime and their initial...
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Bianca Dittrich29/09/2026, 11:50
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Daniele Oriti29/09/2026, 14:10
Quantum gravity is expected to unravel the fundamental quantum structure of spacetime and geometry. In several approaches the very continuum notions of spacetime and geometry are in fact emergent, rather than fundamental, and so is their dynamics. This goes beyond the intuition of effective field theory approaches to quantum gravity, and opens the possibility of quantum gravity affecting also...
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Salvatore Capozziello30/09/2026, 09:30
"We investigate whether the recent DESI DR2 measurements provide or not evidences for dynamical dark energy by exploring the LambdaCDM model and its extensions. Using a comprehensive MCMC analysis with a wide range of cosmological datasets including DESI DR2 BAO, Lyman alpha data, CMBR, BBN, cosmic chronometers, and multiple Type Ia supernova compilations, we assess the statistical preference...
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Antonino Marcianò30/09/2026, 11:00
Suggestions of a late-time phantom crossing from DESI baryon acoustic oscillation measurements combined with cosmic microwave background and Type-Ia supernova observations have renewed interest in dynamical dark energy. We present a realization of low-redshift phantom crossing based on fermion condensation and general relativity. The mechanism arises from the interplay between a...
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Bose Benjamin30/09/2026, 11:50
Connecting fundamental theories of gravity to cosmological observations remains a major challenge: predictions formulated at high energies must be translated into viable low-energy dynamics and ultimately into observable signatures. I will discuss two complementary approaches to this problem. First, I will present new cosmological constraints on a late-time dark-energy scenario motivated by...
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Clare Burrage30/09/2026, 15:30
We do not understand 95% of our Universe. 63% of this unknown is dark energy (or a cosmological constant), which drives the accelerated expansion of the universe and 27% is dark matter, an additional matter component which clumps together to form large halos around visible galaxies. These two dominating components of the universe have only been observed through their gravitational effects, and...
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Niayesh Afshordi01/10/2026, 09:30
Quantum gravity is usually associated with distances near the Planck scale, seemingly far beyond direct experimental reach. But horizons—from black holes to the early Universe and the cosmological horizon—may provide enormous amplifiers of microscopic physics. I will begin with a pedagogical overview of how observations of these systems can turn questions about quantum gravity into falsifiable...
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Olaf Hohm01/10/2026, 11:00
"I will make the case for mathematical physics in general and for the need to formalize QFT and Quantum Gravity in particular, especially in light of AI. Such formalizations seem necessary in order to consolidate (and eventually computer-verify) results in formal high-energy theory and quantum gravity, which have weak community standards. I argue that a significant collection of results in...
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Viktoria Venken02/10/2026, 09:30
If string theory provides a consistent theory of everything, it should make predictions about cosmology that can be checked against observation.
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In spite of this, it has proved incredibly challenging to obtain any concrete testable predictions from string theory.
In the first part of this talk I will give a broad-level overview of the 'landscape' picture of string theory and how the first... -
Robert Brandenberger02/10/2026, 11:00
The BFSS matrix model is a proposed non-perturbative definition of superstring theory. Starting with a thermal state of this model, I will show how a metric spacetime and early universe cosmology can emerge. Thermal fluctuations lead to scale-invariant spectra of cosmological fluctuations and gravitational waves.
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Asato Tsuchiya02/10/2026, 11:50
The type IIB matrix model is a promising candidate for a nonperturbative formulation of superstring theory. In this model, the eigenvalue distribution of the bosonic matrices represents an emergent spacetime, which is determined by the nonperturbative dynamics of the model in the large-N limit. Numerical simulations are therefore indispensable for revealing the structure of the emergent...
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Suddhasattwa Brahma02/10/2026, 14:10
There has been a new line of development for deriving cosmological spacetimes from quantum mechanical Matrix Models. In particular, it has been shown how an expanding metric might be coarse-grained from abstract matrix degrees of freedom, and how one naturally gets a scale-invariant spectrum of primordial perturbations in this model without introducing arbitrary tunable parameters, by...
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