BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Phasing-in dark matter DTSTART;VALUE=DATE-TIME:20250917T134000Z DTEND;VALUE=DATE-TIME:20250917T140000Z DTSTAMP;VALUE=DATE-TIME:20260817T005807Z UID:indico-contribution-113-442@indico.ift.uam-csic.es DESCRIPTION:Speakers: Henda Mansour (Karlsruhe Institute of Technology)\nD espite being an elegant mechanism to explain Dark Matter (DM) production\, freeze-in introduces challenges: If DM interacts via non-renormalizable o perators\, the predictions are highly sensitive to initial conditions\, su ch as the reheating temperature of the universe. These issues are particul arly relevant in models in which the universe deviates from radiation domi nation and the entropy of the Standard Model (SM) thermal bath is not cons erved. \nIn this talk\, I will present a general freeze-in scenario in whi ch a scalar field dominates the energy density of the universe before unde rgoing a first-order phase transition and then slowly decaying to visible particles. The decays lead to a second phase of reheating of the radiation bath and to additional contributions to DM freeze-in. I will explore the conditions under which these late contributions dominate over the initial DM abundance produced at primordial reheating. In this scenario\, referred to as phase-in\, the final abundance of DM is primarily determined by the details of the phase transition and subsequent reheating\, and insensitiv e to the details of inflationary reheating. \nAdditionally\, I will revisi t the commonly made assumption that the universe becomes early matter domi nated after such a phase transition\, discuss scenarios in which this may break down and highlight its relevance to the phase-in mechanism.\n\nhttps ://indico.ift.uam-csic.es/event/29/contributions/442/ LOCATION:IFT UAM/CSIC URL:https://indico.ift.uam-csic.es/event/29/contributions/442/ END:VEVENT BEGIN:VEVENT SUMMARY:New approach for study of dynamics of neutrinos in the primordial era DTSTART;VALUE=DATE-TIME:20250917T132000Z DTEND;VALUE=DATE-TIME:20250917T134000Z DTSTAMP;VALUE=DATE-TIME:20260817T005807Z UID:indico-contribution-113-443@indico.ift.uam-csic.es DESCRIPTION:Speakers: Vsevolod Syvolap (Instituto de Física Teórica)\nCo smological observations\, such as Big Bang Nucleosynthesis (BBN) and the C osmic Microwave Background (CMB)\, provide vital insights into the early U niverse\, allowing us to trace its evolution to times as short as $t \\sim 0.01$ s and to test extensions of the Standard Model. Accurately modeling the non-trivial dynamics of neutrinos typically requires solving a system of Boltzmann equations numerically\, a method that comes with inherent li mitations\, particularly in terms of computational efficiency. In this tal k\, a novel approach based on the Direct Simulation Monte Carlo (DSMC) met hod is presented\, which offers significant advantages over traditional te chniques\, particularly in scenarios involving high-energy neutrino inject ions.\n\nhttps://indico.ift.uam-csic.es/event/29/contributions/443/ LOCATION:IFT UAM/CSIC URL:https://indico.ift.uam-csic.es/event/29/contributions/443/ END:VEVENT BEGIN:VEVENT SUMMARY:Detecting Ultralight Dark Matter with Matter Effect DTSTART;VALUE=DATE-TIME:20250917T130000Z DTEND;VALUE=DATE-TIME:20250917T132000Z DTSTAMP;VALUE=DATE-TIME:20260817T005807Z UID:indico-contribution-113-444@indico.ift.uam-csic.es DESCRIPTION:Speakers: Xucheng Gan (DESY)\nUltralight particles\, with a ma ss below the electronvolt scale\, exhibit wave-like behavior and have aris en as a compelling dark matter candidate. A particularly intriguing subcla ss is scalar dark matter\, which induces variations in fundamental physica l constants. However\, detecting such particles becomes highly challenging in the mass range above $10^{-6}\\\,\\text{eV}$\, as traditional experime nts face severe limitations in response time. In contrast\, the matter eff ect becomes significant in a vast and unexplored parameter space. These ef fects include (i) a force arising from scattering between ordinary matter and the dark matter wind and (ii) a fifth force between ordinary matter in duced by the dark matter background. Using the repulsive quadratic scalar- photon interaction as a case study\, we develop a unified framework based on quantum mechanical scattering theory to systematically investigate thes e phenomena across both perturbative and non-perturbative regimes. Our app roach not only reproduces prior results obtained through other methodologi es but also covers novel regimes with nontrivial features\, such as decohe rence effects\, screening effects\, and their combinations. In particular\ , we highlight one finding related to both scattering and background-induc ed forces: the descreening effect observed in the non-perturbative region with large incident momentum\, which alleviates the decoherence suppressio n. Furthermore\, we discuss current and proposed experiments\, including i nverse-square-law tests\, equivalence principle tests\, and deep-space acc eleration measurements. Notably\, we go beyond the spherical approximation and revisit the MICROSCOPE constraint on the background-induced force in the large-momentum regime\, where the decoherence and screening effects in terplay. The ultraviolet models realizing the quadratic scalar-photon inte raction are also discussed.\n\nhttps://indico.ift.uam-csic.es/event/29/con tributions/444/ LOCATION:IFT UAM/CSIC URL:https://indico.ift.uam-csic.es/event/29/contributions/444/ END:VEVENT BEGIN:VEVENT SUMMARY:Overview of recent results from cosmological observations and impl ications for particle physics DTSTART;VALUE=DATE-TIME:20250917T123000Z DTEND;VALUE=DATE-TIME:20250917T130000Z DTSTAMP;VALUE=DATE-TIME:20260817T005807Z UID:indico-contribution-113-482@indico.ift.uam-csic.es DESCRIPTION:Speakers: Eleonora Di Valentino ()\nhttps://indico.ift.uam-cs ic.es/event/29/contributions/482/ LOCATION:IFT UAM/CSIC URL:https://indico.ift.uam-csic.es/event/29/contributions/482/ END:VEVENT END:VCALENDAR