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Raymond Volkas (U of Melbourne)07/07/2025, 17:00
The standard DFSZ axion model features stable domain walls, so requires a pre-inflationary axion. This means the density of axion dark matter depends on an unknowable initial misalignment angle and thus predictivity is compromised compared to the post-inflationary axion case. I present a systematic classification of flavour-dependent DFSZ Peccei-Quinn symmetry variants that have no domain wall...
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Mohammad Ali Gorji (IBS CTPU-CGA)07/07/2025, 17:30
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...
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Kiwoon Choi (IBS CTPU-PTC)08/07/2025, 09:00
I discuss the PQ quality and scale hierarchy of extra dimensional axions in the context of 5-dimensional orbifold field theory on S^1/Z_2.
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Stefano Scopel (Sogang U)08/07/2025, 09:30
The WIMP indirect detection signal is enhanced by the square of the WIMP density, and celestial bodies can catalyze WIMP annihilation by accumulating WIMPs with their gravitational potential. In particular, WIMP annihilation can induce a GeV neutrino signal from the Sun, the increase of the total luminosity of White Dwarfs in nearby Globular Clusters, or a sizeable radio emission from the Dark...
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Bin Wang (SJTU/Yangzhou)08/07/2025, 10:00
The interaction between DM and DE has been proved successful in alleviating the coincidence problem and shown allowed by observations. The BINGO radio telescope is specifically designed to study the properties of DE and its interaction with DM during the late-time cosmic acceleration. We introduce the BINGO-ABDUS project, its current status, future development and its specific aim at providing...
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Eung Jin Chun (KIAS)08/07/2025, 14:00
We propose a scenario for the cogenesis of baryon asymmetry and dark matter, realizing spontaneous leptogenesisby by Majoron in Type I seesaw model.
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This mechanism requires significant kinetic motion, which we demonstrate can naturally arise from conventional misalignment under conditions of symmetry non-restoration -
Masahiro Kawasaki (ICRR/U of Tokyo)08/07/2025, 14:30
The recent determination of the primordial abundance of He4 suggests that our universe has a large lepton asymmetry. We consider the Q-ball scenario that produces the large lepton asymmetry without generating a large baryon asymmetry. We also discuss the enhancement of gravitational waves and resonant production of sterile neutrinos in the scenario.
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Ue-Li Pen (Academia Sinica)08/07/2025, 15:00
Using the tanh potential as an example, we present a new class of real time instantons corresponding to general equivalence classes. The Euler-Lagrange equation solutions to saddle points are not unique for complex saddles: any contour in the equivalence classes maps to the same action due to Cauchy’s theorem. This new tool resolves a number of existing puzzles, including curved space particle...
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Yudai Suwa (U of Tokyo)08/07/2025, 15:30
Neutrinos emerge promptly from the cores of collapsing massive stars and are the most direct messengers of the microphysics that drives stellar core collapse. Owing to their small interaction cross-sections, they propagate with negligible attenuation, so their time- and energy-dependent flux records the full evolution from shock formation to the birth of a neutron star, or, if accretion...
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Misao Sasaki (APCTP/IPMU)09/07/2025, 09:00
Stochastic gravitational wave backgrounds have become a hot topic in cosmology. However, very few studies have been done on gravitational waves on intergalactic scales. I discuss possible sources on these scales which could even be parity violating, and present a method to probe such gravitational waves.
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Rinku Maji (IBS CTPU-CGA)09/07/2025, 09:30
The grand unified theory (GUT) provides a rationale for the arbitrariness of the Standard Model (SM) and explains many enigmas of nature at the outset of a single gauge group. The GUTs predict the proton decay, and the spontaneous symmetry breaking (SSB) of the higher symmetry group may lead to the formation of topological defects, which are indispensable in the context of cosmological...
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Jun'ichi Yokoyama (IPMU)09/07/2025, 10:00
The phase transition of a false vacuum due to a first-order phase transition has been studied by analysis using Euclidean time conventionally. Such analysis has also been performed for curved spacetimes, and a certain thermodynamic interpretation has been given to phase transitions in de Sitter spacetimes and spacetimes containing black holes. In this talk, I will distinguish myself from such...
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Bum-Hoon Lee09/07/2025, 14:00
Observational data, such as the Hubble constant (H0) and cosmic birefringence, challenge the ΛCDM model. The Hubble tension indicates differing expansion rates between CMB measurements and direct observations of supernovae/Cepheid variables. Cosmic birefringence causes rotation in the CMB polarization plane. We briefly review on the Early Dark Energy Models (EDE) and explain known results that...
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Ryosuke Sato (Osaka U)09/07/2025, 14:30
The annihilation cross section of dark matter has an important role in dark matter phenomenology. If dark matter couples to a light force mediator, the exchange of the mediator non-perturbatively distorts the wave function of the dark matter from the plane wave. This effect significantly modifies the annihilation cross section .This effect is called as the Sommerfeld effect. In this talk, I...
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Yuta Hamada (KEK)09/07/2025, 15:00
On the one hand, it is known that the electroweak symmetry breaking (EWSB) in the Standard Model (SM) is a crossover. On the other hand, in the last decade, the notion of the symmetry has been greatly generalized by recognizing that the symmetry is equivalent to the presence of the topological operators. This enables us to discover new symmetries in the SM. After reviewing how these new...
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Phillip Urquijo (U of Melbourne)09/07/2025, 15:30
SABRE is an international collaboration that will operate similar particle detectors in the Northern (SABRE North) and Southern Hemispheres (SABRE South). This innovative approach aims to distinguish potential dark matter signals from seasonal backgrounds: a pioneering strategy only feasible with a Southern Hemisphere experiment. SABRE South is located at the Stawell Underground Physics...
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Tomo Takahashi (Saga U)10/07/2025, 09:00
High-energy physics often motivates multi-field inflationary scenarios where stochastic effects play a crucial role. Peculiar to multi-field models, the noise-induced centrifugal force results in a longer duration of inflation depending on the number of fields, even when the stochastic noises themselves are small. We show that, in such small-noise regimes, the number of fields generically...
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Ming-Chung Chu (CUHK)10/07/2025, 09:30
The standard Planck ΛCDM model is well known to encounter several tensions when
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confronted with various cosmological data, including the neutrino mass and the DESI BAO
tensions. The former tension refers to the neutrino mass constraint from CMB fitting being
substantially below the lower bound from neutrino oscillation experiments. In the latter, the
BAO scales measured by DESI disagree... -
Sebastian Bahamonde (IPMU)10/07/2025, 10:00
General Relativity is based on Riemannian geometry, where gravity is solely represented by the metric degrees of freedom. This framework can be generalized by introducing torsion and nonmetricity into the underlying geometry. In this talk, I will describe how to construct such theories and how these geometrical quantities might lead to new effects on astrophysical and cosmological scales. I...
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Rong-Gen Cai (ITP/Ningbo)10/07/2025, 14:00
Recently, a 3∼4σ preference for dynamical dark energy has been reported by the Dark Energy Spectroscopic Instrument (DESI) collaboration, which has inspired hot debates on new physics or systematics. In this letter, we reveal that this preference is significantly biased by an external low-redshift supernova (low-z SN) sample, which was combined with the Dark Energy Survey SN program (DES-SN)...
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Tuan Quoc Do (Phenikaa U)10/07/2025, 14:30
Recently, the cosmological principle, an underlying assumption of modern cosmology, has been questioned extensively due to the emergence of observational anomalies associated with not only an early phase but also a late-time phase of our observable universe. Consequently, a stable anisotropic inflation seems to be a reasonable mechanism for connecting an early anisotropic inflationary phase to...
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Arman Shafieloo (KASI)10/07/2025, 15:00
Reconstructing the expansion history of the universe and the properties of dark energy have been among the main goals of physical cosmology. I will discuss reconstructing dark energy in light of the most recent cosmological observations, including DESI-2025 BAO observations, various supernova compilations, and Planck CMB data. I will also discuss some theoretical implications of the parametric...
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Jounghun Lee (SNU)10/07/2025, 15:30
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Xiao-Gang He (TDLI)11/07/2025, 09:00
We explore the potential presence of new physics in the recent NA62 observation of the kaon decay K+ → π++E̸ with missing energy E̸ in the context of a dark-matter (DM) scenario that can explain the Belle II finding of enhanced rate of the b-meson decay B+ → K++E̸ compared to the standard-model expectation, assuming that a light real scalar boson φ plays the role of DM. The DM particle is...
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David McKeen (TRIUMF)11/07/2025, 09:30
Dark sectors which may contain the dark matter required by observation have become increasingly well studied in recent years. One of the virtues of dark matter in a dark sector is the simplicity of such models, allowing for very general results. I’ll discuss recent work on simple dark sectors that naturally give rise to slightly more complicated phenomenology, focusing on models of dark matter...
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Haipeng An (Tsinghua U)11/07/2025, 10:00
The large excursion of the inflaton field can significantly alter the properties of coupled spectator fields during inflation. This dynamic may trigger phase transitions in the spectator sector, leading to rich phenomenological implications. In this talk, I will discuss the observable signatures of such phase transitions, including gravitational waves, topological defects, and primordial...
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Spyros Sypsas (Centro de Ciencias Exactas, UBB)11/07/2025, 14:00
Scalar field theory on de Sitter space suffers from infrared (IR) divergences, highlighting the necessity of nonperturbative methods for IR resummation.
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A well-known triad of statements encapsulates the IR issue:
(1) the massless Bunch–Davies vacuum breaks de Sitter invariance;
(2) the coincident limit of the two-point correlator exhibits secular growth; and
(3) stochastic inflation... -
Shi Pi (ITP)11/07/2025, 14:30
In single-field inflation, an ultra-slow-roll stage is needed to enhance the curvature perturbation ζ to generate primordial black holes (PBHs) on small scales, which is usually accompanied by large local non-Gaussianity. I will introduce the recent progress on the non-Gaussian curvature perturbation of a logarithmic form. It can naturally give rise to an exponential-tail or a double...
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Ying-li Zhang (Tongji U)11/07/2025, 15:00
Primordial black holes (PBHs) are a kind of black holes which may form during the early stage of the universe. In this talk, I will discuss a class of inflationary models which seed the formation of PBHs.
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