Conveners
Early Universe Cosmology
- Yeuk Kwan Edna Cheung (Nanjing University)
Early Universe Cosmology
- Bhaskar Dutta (Texas A&M University)
Early Universe Cosmology
- Michele Cicoli (Università di Bologna)
Early Universe Cosmology
- Yeuk Kwan Edna Cheung (Nanjing University)
Early Universe Cosmology
- Anupam Mazumdar (Groningen University)
We discuss phenomenological viability of a novel inflationary model in the minimal gauge mediated supersymmetry breaking scenario. In this model, cosmic inflation is realized in the flat direction along the messenger supermultiplets and a natural dark matter candidate is the gravitino from the out-of-equilibrium decay of the bino-like neutralino at late times, which is called the superWIMP...
A $t$-channel singularity of a cross section occurs in a $2\to 2$ process when the mediator is allowed to be on-shell, i.e. when the process can be treated as a sequence of a $1\to 2$ decay and a $2\to 1$ inverse decay. If, moreover, the mediator is stable, this singularity cannot be regularized within the common Breit-Wigner approach.
In this talk I will discuss the conditions for the...
We discuss the preinflationary dynamics of the spatially flat FLRW universe filled with a single scalar field that has the generic potentials, in the framework of loop quantum cosmology. The evolution can be divided into two different classes, one is dominated initially (at the quantum bounce) by the kinetic energy of the scalar field, and one is not. In both cases, we identify numerically the...
The Gravity effects play an important role both in the black hole scattering and early universe inflation. On the other hand, extremely heavy dynamic systems, e.x. The black hole and early universe, provide a natural environment for detecting classical and quantum gravitational effects. In this talk, we majorly focus on the theoretical part of the gravity effects. We propose a systematic...
I argue that generic features of string compactifications, namely a high scale of supersymmetry breaking and one or more epochs of modulus domination, can accommodate superheavy neutralino dark matter with a mass around 10^10−10^11 GeV. Interestingly, this mass range may also explain the recent detection of ultra-high-energy neutrinos by IceCube and ANITA via dark matter decay.
A scheme of simplified smooth hybrid inflation is realized in the framework of supersymmetric $SU(5)$. The smooth model of hybrid inflation provides a natural solution to the monopole problem that appears in the breaking of $SU(5)$ gauge symmetry. The supergravity corrections with nonminimal Kahler potential are shown to play important role in realizing inflation with a red-tilted scalar...
The axion is a well-motivated candidate for the inflaton, as the radiative corrections that spoil many single-field models are avoided by virtue of its shift symmetry. However, axions generically couple to gauge sectors. As the axion rolls through its potential, this coupling can result in the production of a co-evolving thermal bath, a situation known as "warm inflation." Inflationary...
Supersymmetric flat directions develop large expectation values in the early universe, leading to formation of SUSY Q-balls and ultimately primordial black holes (PBH). This makes PBHs a natural and generic dark matter candidate in supersymmetry. The PBH masses resulting from supersymmetry naturally fall into the sublunar mass window, where the PBHs can account for all dark matter. We will...
The formation of primordial black hole (PBH) dark matter and the generation of scalar induced secondary gravitational waves (SIGWs) have been studied in the generic no-scale supergravity inflationary models. By adding an exponential term to the K\"ahler potential, the inflaton experiences a period of ultra-slow-roll and the amplitude of primordial power spectrum is enhanced to...
In this talk I will discuss about Higgs inflation in the framework of a minimal extension of the Standard Model gauge symmetry by a U(1)_B−L factor. Furthermore I will talked about physics related to the nature of gravitino, considering possible scenarios, including that it is the lightest supersymmetric particle (LSP) where it can be considered as a DM candidate. The other possibility...
We discuss supergravity inflation in braneworld cosmology for the class of potentials $V(\phi)=\alpha \phi^n\rm{exp}(-\beta^m \phi^m)$ with $m=1,~2$. These minimal SUGRA models evade the $\eta$ problem due to a broken shift symmetry and can easily accommodate the observational constraints. In the high energy regime $V/\lambda\gg 1$, the numerical predictions and approximate analytic formulas...
We consider Hybrid inflation and Tribrid Inflation models in no-scale supergravity framework. We show that a Starobinsky like inflation can be realized with asymptotically flat potentials. U(1)_R symmetry can be broken on the renormalizable level or by Planck suppressed non-renormalizable operators. A connection to the low energy physics as well as the neutrino masses is addressed.
Extensions of the Standard Model (SM) Higgs sector allow for a rich cosmological history around the electroweak (EW) scale. In the context of the next-to 2HDM (N2HDM) we analyse the phenomena of EW symmetry non-restoration as well as vacuum trapping. We show that these phenomena can occur in relevant parts of the parameter space. Focusing on the type II N2HDM and taking into account various...
In the ''Minimal Supergravity Inflation'', whose only degrees of freedom are the (real) inflaton, gravitino, and graviton, an issue of the catastrophic production of slow gravitinos after inflation has been reported. We will briefly comment on the origin of such catastrophic production and propose an alternative model with the same physical degrees of freedom that is free from the issue. We...
Current measurements of Standard-Model parameters suggest that the electroweak vacuum is metastable. This metastability has important cosmological implications because large fluctuations in the Higgs field could trigger vacuum decay in the early universe. For the false vacuum to survive, interactions which stabilize the Higgs during inflation---e.g., inflaton-Higgs interactions or non-minimal...
We for the first time map the range of active-sterile neutrino mixing angles in which leptogenesis is possible in the type I seesaw model with three heavy neutrinos with Majorana masses between 50 MeV and 70 TeV, covering the entire experimentally accessible mass range. Our study includes both, the asymmetry generation during freeze-in (ARS mechanism) and freeze-out (resonant leptotenesis) of...
This talk focusses on constraining the inflaton couplings and reheating temperature by the CMB data in different inflation models. It has been pointed out that within a given inflation model, it is possible to “measure” the inflaton coupling from CMB. The models parameters can be related to the observable CMB data by the reheating parameters. Using the Planck 2018 data, we give constraints to...
We investigate whether successful Gravitational Leptogenesis can take place during an Ekpyrotic contraction phase. Two possible paths by which this can occur are coupling the Ekpyrotic scalar to a gravitational Chern-Simons term, or to a U(1) gauge field Chern-Simons term. These couplings lead to the production of chiral gravitational waves, which generate a lepton number asymmetry through the...
We investigate the possibility of simultaneously explaining inflation, the neutrino masses and the baryon asymmetry through extending the Standard Model by a triplet Higgs. The neutrino masses are generated by the vacuum expectation value of the triplet Higgs, while a combination of the triplet and doublet Higgs' plays the role of the inflaton. Additionally, the dynamics of the triplet, and...
The well-known Hubble tension is widely thought to be an indication of new physics beyond $\Lambda$CDM. Theoretical modification happening before recombination (early) seems to be more viable than post-recombination (late) ones since they are less constrained by observations. We propose the AdS-EDE model which solves the tension at 1$\sigma$ level for the first time while remaining compatible...
In this talk I will discuss a simple model of maximal axion misalignment. Maximally-misaligned axions with masses larger than 10^{-22} eV constitute an attractive DM candidate with interesting phenomenology. On the other hand, maximally-misaligned axions with masses m=O(1-100)H_0 generically behave as dark energy with a decay constant that can take values well below the Planck scale, avoiding...
In the axion-gauge fields model, the nontrivial configuration and dynamics of the axion and hidden gauge fields during inflation induce gravitational wave background. In particular, the energy density of the axion needs to be sufficiently large to generate observable gravitational waves. After inflation ends, the axion decays into gauge fields, and they behave as dark radiation, which modifies...
The universe according to the tetron model consists of invisible tiny constituents, elastically bound with bond length about the Planck length and binding energy the Planck energy.
A tetron transforms as the fundamental fermion(=octonion) representation 8 of SO(6,1). With respect to the decomposition SO(6,1)-->SO(3,1)xSO(3) a tetron possesses spin 1/2 and isospin 1/2, i.e. it represents an...
warm axion inflation has been introduced as an alternative to standard (cold) inflation. Coupling between inflaton (axion) field and gauge fields changes the evolution of scalar field even at the background level. It was discussed that the system with this coupling can be thermalized inherently and is protected against tachyonic instability. I will discuss that this scenario is compatible with...
We study primordial black holes (PBHs) formation in the excursion set theory (EST) in a vast range of PBHs masses with and without confirmed constraints on their abundance. In this work, a new concept of the first touch in the EST is introduced for PBHs formation which takes into account the earlier horizon reentry of smaller masses. Our study shows that in the EST, it is possible to produce...
In this talk we will present a mechanism for matter generation in a string-inspired bounce universe. Utilizing the coupling between a higgs-like scalar field and the tachyon emerged from the D-brane and anti-D-brane co-annihilation, we study the conversion between tachyon and standard model fields. During the matter-dominated contraction phase the SM particles that are produced by tachyon...
