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Kamil Mudrunka28/09/2026, 15:45
"Cosmological inflation predicts the existence of primordial gravitational wave background. Originating as quantum fluctuations of the metric during inflation, slow roll inflation models predict a nearly flat spectrum for modes that exit the Hubble horizon during the accelerated expansion epoch. The spectrum naturally extends to high frequency modes that never enter the superhorizon regime....
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Pankaj Saha28/09/2026, 16:00
Inflation is almost always described as small ripples on a fixed, smooth background --- but that picture is expected to break down when fluctuations grow large. We push into that regime with 3+1 lattice simulations in which the field and the local expansion evolve together. This lets us follow inflation into the strongly nonlinear regime relevant for primordial black holes, where the power...
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Minxi He28/09/2026, 16:15
In this talk, I will discuss the preheating dynamics in Higgs inflation in the Einstein-Cartan formalism, especially focusing on unitarity violation. It is known that Einstien-Cartan gravity provides a framework for a broad class of Higgs inflation models, including the metric and Palatini Higgs inflation. It smoothly connects these two limits by the coupling between Higgs and the Nieh-Yan...
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Nils A Nilsson28/09/2026, 16:30
Spacetime-symmetry breaking provides a well-motivated avenue for probing departures from general relativity and possible low-energy signatures of quantum gravity. I will discuss theoretical consistency conditions that arise when diffeomorphism symmetry is broken, focusing on the distinction between explicit and spontaneous breaking and the associated constraints on the gravitational dynamics....
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Hongguang Liu29/09/2026, 15:45
Effective quantum gravity models often specify corrections to homogeneous cosmological evolution, leaving open how these corrections extend to cosmological perturbations. I will present a framework for constructing scalar and tensor perturbations around a given modified FLRW background. Here, spatial covariance and a Birkhoff-type vacuum requirement constrain its extension to inhomogeneous...
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Tatsuya Daniel29/09/2026, 16:00
In this talk, I will revisit the inflationary quantum cosmology framework where the Ashtekar formulation of gravity minimally coupled to a scalar field admits a full non-perturbative quantum minisuperspace description of inflation. By extending prior analytic treatments, I will show how inflation can be a robust dynamical attractor across a wide range of scalar potentials, even with mild...
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Farbod Sayyed Rassouli29/09/2026, 16:15
"Different notions of time arise from different choices of observer. In cosmological settings, a particularly natural choice is spacetime volume, which is conjugate to the cosmological constant. This gives rise to unimodular time, deparametrizing the Wheeler–DeWitt equation into a Schrödinger-like evolution equation. I will first explain how this construction appears in arbitrary dimensions,...
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Cristiano Sampaio29/09/2026, 16:30
"A central goal at the interface of quantum gravity and cosmology is to characterize spacetime in purely relational, coordinate-independent terms. In early-universe cosmology, observational access to spacetime geometry is mediated not through coordinates, but through the spectral modes of quantum fields and their higher-order correlators. However, the spectrum of a linear wave operator alone...
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Taishi Sano29/09/2026, 16:45
"A promising route toward understanding how spacetime may emerge from quantum gravity is to regard gravitational dynamics in minisuperspace as a hydrodynamic or collective limit of the underlying theory. One intriguing indication of such an emergent structure is the recurring appearance of Schrödinger symmetry in a variety of minisuperspace models. While recent work in quantum cosmology has...
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Tucker Manton30/09/2026, 14:15
3-form dark energy is similar to but distinguishable from a scalar field in an expanding universe, and its tensorial structure allows for couplings that cannot be experienced by canonical scalars. We here explore the possibility that 3-form dark energy can explain the cosmic birefringence angle β ~ 0.3 degrees, as suggested by observations of the CMB polarization. We consider two EFT-inspired...
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Benjamin Muntz30/09/2026, 14:30
"What can solve the cosmological constant problem?
We present a modern interpretation of the problem of radiative corrections to vacuum energy from the point of view of generalised symmetries; in particular global (-1)-form symmetries associated with continuous couplings. It is generally argued that quantum gravity does not admit global symmetries. We point out that general relativity with...
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Masroor Pookkillath30/09/2026, 14:45
"We construct a linearly stable scalar-field model that realizes both an
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upward crossing of the dark-energy equation of state, from $w_{\rm DE}<-1$ to $w_{\rm DE}>-1$, and weakened gravitational clustering in the cold dark matter (CDM) sector. An exponential potential breaks shift symmetry and drives the background from a stable phantom phase toward the nonphantom regime, while a pure... -
Savvas Koushiappas30/09/2026, 16:30
The standard cosmological model lacks a microphysical origin for cosmic acceleration, while recent observations show hints of dynamical dark energy. Quantum gravitational corrections are conventionally assumed to be confined to the Planck scale, but quantum kinematic principles—much like the Heisenberg uncertainty principle—can influence dynamics across macroscopic scales. I will discuss a...
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56. New paths towards the first detection of primordial non-Gaussianities from large-scale structureMinh Nguyen30/09/2026, 16:45
"Measuring primordial non-Gaussianities will open a new window to study quantum fluctuations and interactions during inflation. A detection of non-zero PNGs in either the cosmic microwave backgroun (CMB) or large-scale structure (LSS) however proves to be elusive. Current and upcoming LSS 3D maps will provide data with competitive and better statistical power than the CMB 2D map---provided...
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Camilla Lavino01/10/2026, 11:50
I will present a way to use Exceptional Field Theory to compute the spectrum of Kaluza-Klein modes for a set of backgrounds that can be uplifted from a 5-dimensional theory through consistent truncation. To this end, I will employ the formulation of field theory in terms of $L_{\infty}$ algebras and homotopy transfer, which maps the gauge redundant fields of supergravity to a theory with just...
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Xin-Chen He01/10/2026, 12:05
At the interface between quantum gravity and cosmology, evaporating ultra-light primordial black holes (PBHs) provide a novel probe of Hawking radiation through distinctive stochastic gravitational-wave (GW) signatures. This talk will first review how induced GWs are generated via the so-called poltergeist mechanism and how these signals can probe small-scale primordial non-Gaussianity. The...
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Yoshiyuki Watabiki01/10/2026, 12:20
We show how our Universe can emerge from symmetry breaking in a W_3 algebra whose components form a Jordan algebra. The underlying one-dimensional spaces with different flavors, or components, are knitted into a higher-dimensional spacetime through a knitting mechanism, with three-dimensional space emerging as part of this structure. Algebraically, the knitting mechanism is characterized by...
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Vikramaditya Mondal01/10/2026, 12:35
The Lorentzian gravitational path integral over homogeneous and isotropic metrics in a closed universe with positive cosmological constant is dominated by complex saddle points, such as the Hartle–Hawking saddles. We ask how to compute cosmological correlators on such complex backgrounds, and how they change with respect to shifts of the kinematic variables — the kinematic flow — without...
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47. Regularized Master-Field Approximation for Mass-Deformed Supersymmetric Yang–Mills Matrix ModelsReishi Maeta02/10/2026, 15:45
Matrix models offer a framework in which spacetime can emerge dynamically without assuming a fixed background geometry. Supersymmetric Yang–Mills matrix models are particularly interesting from a physical perspective, but their numerical study is hindered by the sign problem associated with the complex Pfaffian. A possible approach to this difficulty is the regularized master-field...
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Yutaka Tamaura02/10/2026, 16:00
In contemporary holographic cosmology, the bulk-boundary correspondence is understood via dynamic quantum error-correcting codes and quantum extremal surfaces, where isometric encodings typically guarantee strict unitariness and time-reversible mapping in Hermitian setups [1-3]. However, this conventional framework encounters a profound bottleneck when addressing non-equilibrium cosmological...
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Deha Kaykı02/10/2026, 16:15
"Symmetric teleparallel gravity provides a geometrically distinct route to extending General Relativity, but a viable cosmological model must remain consistent across both cosmological and local gravitational regimes. We investigate an analytic infrared-completed f(Q) model designed as a controlled deformation of the symmetric teleparallel equivalent of General Relativity (STEGR).
The...
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Mohammad Faiz Khan02/10/2026, 16:30
This thesis explores a Lorentz-violating modification of gravity through the inclusion of a massive Kalb-Ramond (KR) field coupled nonminimally to curvature. Motivated by the need to probe gravitational dynamics in ultra-low acceleration regimes where General Relativity and Newtonian gravity may be incomplete, we develop a post-Newtonian framework to study wide binary systems as natural...
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Lina Yildiz02/10/2026, 16:45
"We investigate a covariant extension of General Relativity in which the local effective dimension of spacetime is promoted to a dynamical, curvature-induced degree of freedom on an underlying four-dimensional manifold. Deviations from four dimensions are encoded through a scalar field ε(x), defining D_eff(x)=4−ε(x), which enters the gravitational action through a dimension-dependent weight...
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Gaurav Narain
Gravitational path-integral over R\times S^3 complex metrics with fluctuations is studied in 4D for Einstein-Hilbert gravity in Lorentzian signature, with the aim to investigate the IR properties of complex saddles for various boundary choices. General covariance doesn't allow arbitrary boundary choices for the background and fluctuations. In the ADM-decomposition, while imposing...
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Abishek Balakrishnan
"Supermassive Black Holes (SMBHs) are believed to be at the center of all massive galaxies, as inferred from observations of Quasars over the years, which places a strong constraint of ∼ 10^9M⊙ at z ∼ 6 on these objects. However, how smaller progenitor seeds for these SMBHs are formed at high redshifts remains an open question. In this work, we investigate the formation of these seeds through...
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