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Nils A. Nilsson15/10/2024, 13:50
Recently, a CMB signal of parity violation in the form of isotropic cosmic birefringence has been claimed, a signal consistent with being produced through an axion-photon coupling. In this talk, I will introduce a generic EFT constructed for studies of spacetime-symmetry breaking. Focusing on the photon sector, I will show that a CPT-odd EFT term in fact takes the same form as an axion-photon...
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Yuki Sakakihara15/10/2024, 15:00
We study a simple axionlike model with two complex scalar fields under global U (1) symmetry. The charge of one scalar field is double the other one. A particular feature of our model is that a vacuum manifold is a torus knot, resulting in the formation of a string-wall network. We numerically show that the network becomes a network of narrow strips of string-wall composites (a “kishimen”...
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Albert Escrivà15/10/2024, 15:40
Numerical simulations have been instrumental in advancing our understanding of Primordial Black Hole (PBH) formation and in providing precise estimates of their abundance in the Universe. Traditionally, these simulations have assumed spherical collapse, but indeed, the most realistic initial configuration is an ellipsoid. In this presentation, I will discuss recent findings on non-spherical...
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Masamune Oguri15/10/2024, 16:40
Caustic crossings are highly magnified individual stars observed in high magnification regions of massive galaxy clusters. The first discovery was reported in 2018, and the number of detections is rapidly increasing thanks to James Webb Space Telescope. In this talk I will discuss how we can use caustic crossings for probing nature of dark matter.
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Yikun Wang16/10/2024, 09:30
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Takumi Fujimori16/10/2024, 10:10
The search for dark matter using gravitational wave detectors is attracting significant attention. These detectors have extremely high sensitivity to small displacements, which could be used to detect interactions with ultralight dark matter. Different models predict that dark matter interacts with gravitational wave detectors through various mechanisms. This sensitivity to displacement could...
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Junseok Lee16/10/2024, 11:00
We study the dynamics of axions at first-order phase transitions in non-Abelian gauge theories. When the duration of the phase transition is short compared to the timescale of the axion oscillations, the axion dynamics is similar to the trapped misalignment mechanism. On the other hand, if this is not the case, the axions are initially expelled from the inside of the bubbles, generating axion...
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Fumihiro Naokawa16/10/2024, 11:20
Recently, several papers have reported so-called 'Cosmic birefringence', which is a rotation of the direction of linear polarization of CMB. This might be a hint of new physics beyond standard models because the signal means large scale parity violation of this universe. The reported angles of the rotation are ~0.3 deg. However, we point out there is a nπ phase ambiguity for the angle. This...
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Tasuya Ogawa16/10/2024, 11:40
Oscillons are soliton-like localized configurations formed by real scalar fields. In the context of cosmology, it is predicted that oscillons are formed in inflationary models or axion models, and they are suggested to be the origin of gravitational waves or the seeds of primordial black holes. Typically, oscillons are studied in the context of a single real scalar field. However, the...
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Tatsumi Nitta16/10/2024, 14:00
A DFSZ axion search needs a detector that has an extreme sensitivity to photons. Due to its huge electric dipole moment and intrinsic low noise feature, superconducting qubits are an excellent candidate for the searches. In this talk, we introduce ways to utilize superconducting qubits in dark matter searches and these experimental statuses. Also, we mention a strategy for axion searches...
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Hinata Takidera16/10/2024, 14:40
Axion and Axion-Like Particles (ALPs) are one of the candidates of dark matter. Axion weakly interacts with photon, electron, proton and so on. Many experiments have been proposed by using the axion-photon conversion under magnetic fields. However, axion has not been observed yet. Our research group has proposed Dark matter Axion search with riNg Cavity Experiment (DANCE). DANCE aims to...
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Toshihiro Fujii16/10/2024, 15:00
Extensive air showers induced from high‐energy cosmic rays provide a window into understanding the most energetic phenomena in the universe. We report on visualizing high energy particles of these showers with the silicon imaging detector Subaru Hyper Suprime‐Cam. This method has the advantage of being able to measure individual secondary particles with unprecedented resolution and might be...
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Kai Murai16/10/2024, 15:50
We propose a new mechanism for isotropic cosmic birefringence with an axion-like field that rapidly oscillates during the recombination epoch. In conventional models, the field oscillation during the recombination epoch leads to a cancellation of the birefringence effect and significantly suppresses the EB spectrum of the cosmic microwave background (CMB) polarization. By introducing an...
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Kodai Sakurai16/10/2024, 16:10
Axion is a strong candidate for dark matter and has several types of production mechanisms. While the misalignment mechanism has been well-known since long ago and is usually assumed, thermal productions are another attractive possibility. In this talk, we will discuss thermal productions of the axion in DFSZ-type axion models, which involve heavy additional Higgs bosons. Interestingly, in...
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Joerg Jaeckel16/10/2024, 16:30
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Qiuyue Liang17/10/2024, 09:30
The majoron is a well-motivated light (pseudo-Nambu-Goldstone) boson associated with the spon- taneous breaking of a global lepton-number symmetry. In this letter, we relate the spontaneous breaking scale and its soft-breaking mass by requiring that the majoron is the main component of the dark matter. An electromagnetic-anomalous coupling can be induced by minimally modi- fying the original...
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Deheng Song17/10/2024, 10:30
The Galactic Center Excess (GCE) detected by Fermi-LAT resembles a signal of WIMP dark matter annihilation, although it may also be attributed to a population of millisecond pulsars in the inner Milky Way. I will discuss recent updates in studying the morphology of the GCE. I will show that the bulge model based on the latest VVV survey is consistently favored by data. I will also show that...
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Kohei Hayashi17/10/2024, 10:50
Dark matter is now known to be the vital ingredient for the growth of structure in the Universe, but its nature remains a mystery. Dark matter on the small mass scales, such as within galactic and sub-galactic structures, may well be the key to shedding light on fundamental properties of dark matter and new physics. In particular, revealing dark matter distributions in less massive...
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