Inflation 2025

Contribution List

63. Welcome

12/1/25, 10:00 AM

2. Fabio Finelli, CMB constraints on inflation and perspectives for future observations

12/1/25, 10:15 AM

3. Lennart Balkenhol, Implications for Inflation of the CMB-BAO tension

12/1/25, 11:00 AM

The scalar spectral index, ns, plays a central role in testing inflationary models, with its precise value shaping theoretical and observational priorities. Recent analyses combining the latest cosmic microwave background (CMB) and baryon acoustic oscillation (BAO) data suggest a shift toward higher ns values compared to the Planck results. This comes with implications for inflation;...

52. Antonio Raffaelli, Knot reconstruction of the scalar primordial power spectrum with Planck, ACT, and SPT CMB data

12/1/25, 11:15 AM

We investigate a non-parametric Bayesian method for reconstructing the primordial power spectrum of scalar perturbations using temperature and polarisation data from the Planck, ACT, and SPT CMB experiments. We use the reconstructed scalar primordial power spectrum to derive several quantities related to inflationary dynamics, such as the effective scalar spectral index, slow-roll parameters...

53. Emanuele Fondi, N-body simulations of primordial features with GENGARS

12/1/25, 11:30 AM

Primordial non-Gaussianity (PNG) represents a window into the nature of inflation, and large-scale structure (LSS) surveys can promisingly sharpen its constraints. To fully exploit this potential, cosmological simulations play a crucial role, allowing us to study the signatures and test the detectability of primordial features from LSS. I will present GENGARS, a framework to generate...

54. Zucheng Gao, Parity in Composite-Field Galaxy Correlators

12/1/25, 11:45 AM

Detecting parity violation on cosmological scales would provide a striking clue to new physics. Large-scale structure offers the raw statistical power -- many three-dimensional modes -- to make such tests. However, for scalar observables, like galaxy clustering, the leading parity-sensitive observable is the trispectrum, whose high dimensionality makes the measurement and noise estimation...

6. Zhong-Zhi Xianyu, Analytical routes to massive inflationary correlators

12/1/25, 2:00 PM

7. Hayden Lee, A Hidden Pattern in Cosmological Correlators

12/1/25, 2:45 PM

8. Arthur Poisson, de Sitter momentum space

12/1/25, 4:00 PM

9. Nathan Belrhali, Dual space for cosmological correlators

12/1/25, 4:15 PM

10. Xi Tong, Unitary renormalisation and the quantum breaking of cosmological reality

12/1/25, 4:30 PM

Cosmological correlators and the associated wavefunction coefficients serve as a smoking gun towards the physics of inflation at high energy scales. In minimal setups of single-field inflation, wavefunction coefficients are purely real at tree-level due to unitarity, locality and scale invariance, leading to the so-called no-go theorems on parity violation. Such parity-violating correlators...

55. Xiangwei Wang, Interact or Twist, Cosmological Correlators from Field Redefinitions Revisited

12/1/25, 4:45 PM

In cosmology, correlation functions on a late-time boundary can arise from both field redefinitions and bulk interactions, which are usually believed to generate distinct results. In this letter, we propose a counterexample showcasing that correlators from local field redefinitions can be identical to the ones from bulk interactions. In particular, we consider a two-field model in de Sitter...

11. Thomas Colas, The Open Effective Field Theory of Inflation

12/2/25, 9:00 AM

Effective field theories in particle physics are usually designed for experiments where the initial state — the vacuum before a scattering event — is as clean and isolated as possible. Yet many physical systems, from condensed matter to cosmology, evolve in noisy and dissipative environments. Over the past decade, this recognition has driven progress at the interface between high-energy...

12. Cliff Burgess, Acceleration Then and Now

12/2/25, 9:45 AM

27. Fumiya Sano, Decoherence of primordial perturbations in the view of a local observer

12/2/25, 11:00 AM

We study quantum decoherence of curvature perturbations at superhorizon scales caused by the gravitational nonlinearities. We show that cubic gravitational couplings, constrained by the spatial diffeomorphism invariance, lead to infrared (IR) and ultraviolet (UV) divergences in the decoherence rate at one loop. These divergences arise from fluctuations of deep IR modes which look like a...

28. Francescopaolo Lopez, Quantum signatures and decoherence during inflation from deep subhorizon perturbations

12/2/25, 11:15 AM

In order to shed light on the quantum to classical transition of the primordial perturbations in single field inflation, we investigate the decoherence and associated quantum corrections to the correlation functions of large-scale (superhorizon) scalar curvature perturbations. The latter are considered as an open quantum system which undergoes decoherence induced by a time-dependent...

29. Lennard Dufner, An Open System Approach to Gravitational Waves

12/2/25, 11:30 AM

Several major open problems in cosmology involve spacetime-filling media with unknown microphysics, and can only be probed through their gravitational effects. This observation motivates a systematic open-system approach, in which gravity evolves in the presence of a generic, unobservable environment. In this talk, I will present a general framework for open gravitational dynamics, based on...

56. Sebastian Cespedes, On the UV realisations of \lambda phi^4 in de Sitter

12/2/25, 11:45 AM

I will present an effective field theory (EFT) that captures the dominant late-time behavior of massless spectator fields in de Sitter space in the presence of heavy internal fields. As expected, when the mass of these internal fields is large, the leading term reproduces the infrared-divergent contributions to correlation functions obtained in the single-field description. Remarkably, even...

13. Angelo Caravano, A Tale of Cosmic Butterflies: a non-perturbative journey into the physics of inflation

12/2/25, 2:00 PM

14. Dick Bond, Have quantum Transport, Will Travel: pinGponG theory in Cosmic SuperWeb Inflation propagated to entangled lensed Websky-lightcone maps

12/2/25, 2:45 PM

A major CITA concentration is spatially concentrated primordial nonGaussianities (pinGs) from outlier trajectories (ponGs) which can arise generically during and after inflation from field-instabilities transverse to the inflaton flow. CMB and LSS lightcone Webskys we construct with pinGs can evade the stringent 2D perturbative single-nonG-template constraints from the ~10 e-folds probed by...

30. Tom Morrison, All things in the theory of pinG ponGs: generic primordial intermittent nonGaussianity and outlier trajectories in scalar and correlated gravitational wave signals

12/2/25, 4:00 PM

I will summarize key results from a series of 4 papers in collaboration
with Dick Bond and Jonathan Braden: (1) Relating stochastic inflation to
the results of state-of-the-art lattice simulations, complete with
component separation of nonGaussianity; (2) Spatial localization of
primordial intermittent nonGaussianity (pinGs) and the statistics of
rare events; (3) The role of outlier...

31. Yoann Launay, Stochastic Inflation in Numerical Relativity

12/2/25, 4:15 PM

A set of 3+1 equations for stochastic inflation can be obtained in a gauge invariant manner, incorporating all scalar and tensorial perturbation degrees of freedom and without gradient expansion. We demonstrate a numerical implementation of the stochastic equations cast in the BSSN formulation of Numerical Relativity.

32. Alessio Notari, The Inflationary QCD Axion

12/2/25, 4:30 PM

The QCD axion is a leading Dark-Matter candidate, typically studied in two cosmological scenarios: a 'post-inflationary' regime, in which axionic cosmic strings form after inflation, and a 'pre-inflationary' regime, in which the axion field is homogenized across the observable Universe and no strings are present. Here I explore a third possibility, in which the axion acquires large...

57. Andrea Costantini, Primordial correlators from Multi-point propagators

12/2/25, 4:45 PM

Accurate predictions of correlators of the primordial curvature perturbation are
critical for connecting inflationary models to cosmological observations. Numer-
ical methods employing differential equations, such as the transport approach,
have been extensively used to compute the evolution of these correlators. In this
talk, I will present a novel numerical implementation of the...

51. Outreach public talk, Sébastien Renaux-Petel (in French)

12/2/25, 7:30 PM

15. Yuko Urakawa, Advances in the separate universe approach: from theory to applications

12/3/25, 9:00 AM

16. Matteo Braglia, One-loop renormalized inflationary power spectra

12/3/25, 9:45 AM

36. Oliver Janssen, Constraints on inflation from the gravitational path integral

12/3/25, 11:00 AM

We will review a proposal for which complex geometries should be included as saddle points in the semiclassical evaluation of gravitational path integrals, including a new efficient algorithm to detect violating saddles. Then we will turn to the application of constraining inflation via the Hartle-Hawking wave function.

37. Arttu Rajantie, A Tale of Two Potentials

12/3/25, 11:15 AM

The effective potential of a scalar field is a powerful tool in quantum field theory. Loosely speaking, it can be interpreted as the quantum corrected classical potential of the field, and in cosmology it is widely used to describe the evolution of the inflaton and other scalars during inflation and vacuum transition probabilities, among other things. However, for light scalar fields its...

38. Sriramkumar Lakshmanan, Departures from slow roll inflation and magnetogenesis

12/3/25, 11:30 AM

The primordial magnetic fields are generated during inflation by breaking the conformal invariance of the electromagnetic action through a coupling to the inflaton. Often, a parity violating term is also added to the action to generate helical magnetic fields. In this talk, I will first show that departures from slow roll inflation (as it occurs in scenarios involving a phase of ultra slow...

58. Oksana Iarygina, Axion inflation with non-Abelian gauge fields

12/3/25, 11:45 AM

Currently, the search for primordial gravitational waves is largely focused on detecting the parity-odd polarization pattern in the Cosmic Microwave Background - the B-modes. Accurately interpreting B-mode measurements depends heavily on understanding their production mechanisms. A particularly compelling scenario involves gravitational wave generation through the interaction of axion with...

17. Mario Ballardini, Euclid: constraints on initial conditions and implications for primordial features

12/3/25, 2:00 PM

18. Adam Andrews, Bayesian Field-Level Inference of Local Primordial non-Gaussianity in Galaxy Redshift Surveys

12/3/25, 2:45 PM

34. Poster presentations

12/3/25, 4:00 PM

19. Juan Garcia-Bellido, Primordial Black Holes as a signature of Inflation

12/4/25, 9:00 AM

20. Chiara Animali, Stochastic trees for stochastic inflation and primordial black hole formation

12/4/25, 9:45 AM

During inflation, quantum vacuum fluctuations are stretched beyond the Hubble radius, modifying the large-scale dynamics of the Universe. While their backreaction is negligible in the perturbative regime, it can become important in scenarios leading to primordial black hole (PBH) formation, where large density fluctuations are generated. The combination of stochastic inflation and the 𝛿N...

42. Ilia Musco, Primordial Black Hole formation from a massless scalar field

12/4/25, 11:00 AM

We have investigated primordial black holes formation within a model of the early Universe dominated by a massless scalar field, developing a numerical spherically symmetric code dedicated to this problem. Imposing initial conditions on super horizon scales using the gradient expansion approach, we show that a massless scalar filed is equivalent to a perfect fluid, where the pressure is equal...

43. Eemeli Tomberg, Curvature profiles from stochastic inflation

12/4/25, 11:15 AM

Stochastic inflation is a method for computing super-Hubble perturbations beyond the small-perturbation limit. I show how to obtain the radial profile of the curvature perturbations in a random patch of space using this method. The profiles turn out to be spiky, far from the smooth mean profiles often considered in the literature. Based on extensive numerical simulations, I discuss the...

44. Ricardo Zambujal Ferreira, Stupendously Large Primordial Black Holes and Domain Walls

12/4/25, 11:30 AM

The inflationary diffusion of scalar fields with discrete symmetries can generate a gas of closed domain walls after inflation, which later collapse into primordial black holes (PBHs) upon horizon re-entry. This mechanism predicts a distinctive, nearly flat PBH mass distribution, avoiding some issues of critical collapse. We show that QCD axion models with decay constants near the inflationary...

59. Shiqian Hu, Primordial black holes and False Vacuum Decay

12/4/25, 11:45 AM

The Hawking evaporation of primordial black holes (PBHs) induces local reheating of the Universe, generating transient hot spots that persist over their evaporation timescale. Within this framework, we develop a method to compute the decay rate of metastable vacua in cosmological settings, circumventing conceptual issues associated with the Hartle–Hawking and Unruh vacua. Applying our approach...

21. Oliver Philcox, Colliders in the Sky: Constraining Primordial Non-Gaussianity with CMB and LSS Observations

12/4/25, 2:00 PM

22. Josu Aurrekoetxea, Numerical relativity in the early universe

12/4/25, 2:45 PM

39. Kai Hei Trevor Cheung, Massive spinning fields during inflation

12/4/25, 4:00 PM

We compare two setups incorporating new massive spinning degrees of freedom during inflation within the framework of the effective field theory of inflation (EFToI). Even though they differ on which symmetries are linearly realised, since they couple to the inflaton, it is possible they yield same signatures on cosmological correlators. We will see that their signatures are the same at...

40. Denis Werth, Positive Geometry in Cosmological Correlators

12/4/25, 4:15 PM

41. Chen Yang, Strongly Coupled Sectors in Inflation

12/4/25, 4:30 PM

Understanding the microscopic origin of primordial fluctuations remains a central challenge in inflationary cosmology. In this talk, I will explore a scenario where curvature perturbations interact with a strongly coupled, gapless sector known as unparticles. This setup allows for analytic control of cosmological correlators and reveals novel bispectrum shapes with distinctive phenomenological...

60. Yuhang Zhu, The Integro-differential Bootstrap for Cosmological Correlators

12/4/25, 4:45 PM

23. David Wands, Large/rare fluctuations from stochastic inflation

12/5/25, 9:00 AM

24. Gonzalo Palma, On the infrared behavior of QFTs in de Sitter: loops, logarithms and the stochastic formalism

12/5/25, 9:45 AM

48. Spyros Sypsas, Revisiting stochastic inflation with perturbation theory

12/5/25, 11:00 AM

Using perturbation theory, we compute the one-point probability density function for primordial fluctuations valid to first order in the potential. We examine under which conditions our solution respects the Fokker-Planck equation encountered within the stochastic approach. We identify discrepancies and elucidate their origins, allowing us to shed light on the status of the stochastic formalism.

49. Nadine Nussbaumer, Light scalars in de Sitter: the stochastic story

12/5/25, 11:15 AM

Light, polynomially self-interacting scalars in de Sitter notoriously generate infrared (IR) divergences: on superhorizon scales, their fluctuations grow so large that perturbation theory breaks down. We address this problem using non-perturbative techniques from stochastic inflation, by encoding the superhorizon dynamics in a probability distribution involving composite operators of the light...

50. Jaime Calderon Figueroa, Stochastic instantons and the tail of the inflationary density perturbation

12/5/25, 11:30 AM

In the stochastic $\delta N$ formalism, the statistics of the primordial density perturbations can be mapped to the first-passage distribution of a stochastic process. In this talk, I will present a general framework to evaluate the rare-event tail of this distribution, based on an instanton approximation to a path integral representation of the transition probability. I will show how this...

61. Riccardo Impavido, Inflationary Fossils Beyond Perturbation Theory

12/5/25, 11:45 AM

In this work we provide the missing link between two approaches aimed at characterizing the effect of long perturbation modes in Inflation. We consider the Inflationary Fossils' approach (arXiv:1203.0302 and related works) that characterizes the power-spectrum of the inflaton field in presence of other long and non dynamical fossil fields, and a technique, appeared in arXiv:2103.09244, that...

25. Jacopo Fumagalli, Inflation at small scales: from theoretical progress to GW observatories

12/5/25, 2:00 PM

26. Shi Pi, Nonlinearity of the curvature perturbation on superhorizon scales

12/5/25, 2:45 PM

45. Mariam Tarek Mohamed Abdelaziz, The Effects of Primordial Gravitational Waves on the Large-Scale Structure

12/5/25, 4:00 PM

Primordial Gravitational Waves (PGWs) are a key prediction of inflation, with ongoing efforts to detect them through CMB polarization patterns and direct interferometric searches. In this talk, I will present a novel approach to probing PGWs through their impact on Large-Scale Structure (LSS). While PGWs are often assumed to have a negligible effect on structure formation, our study shows that...

46. Mohammad Ali Gorji, Oscillations and parity violation in gravitational wave background from extra tensor modes

12/5/25, 4:15 PM

Spectator fields which provide additional tensor degrees of freedom, on top of the standard metric tensor perturbations, can produce significant amounts of gravitational waves (GWs). Employing the effective field theory approach for spin-2 fields, we find a universal prediction that linear mixing between the metric and extra tensor modes inevitably induces oscillatory features in the GW...

47. Hugo Holland, The separate universe approach and gauge fixing procedures for multifield inflation models.

12/5/25, 4:30 PM

The separate universe approach (SUA) is a powerful tool offering us a simple way to compute cosmic inhomogeneities at large scales including their non-linear evolution. It consists in describing the universe as a collection of independent patches which are taken to be homogeneous and isotropic. The assumptions one has to do to apply the SUA and its simplifications need to be checked, notably...

62. Jan Tränkle, Constraining the inflaton potential with gravitational waves from oscillons

12/5/25, 4:45 PM

Observations of the cosmic microwave background (CMB) lend strong evidence for the paradigm of cosmic inflation, but the specific form of the inflaton potential remains unknown. Under certain conditions, the oscillating inflaton condensate filling the Universe after inflation can fragment and form interesting non-linear structures known as oscillons. These long-lived soliton-like field...

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1. Invited talk