| 7 (Tue) | 8 (Wed) | 9 (Thu) | 10 (Fri) |
|---|---|---|---|
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15:00 - 15:30 Coffee Break 15:30 - 17:00 Brainstorming discussion after overview talks |
14:00 - 15:00 Seminar M. Amin [pdf] 15:00 - 15:30 Coffee Break |
15:00 - 15:30 Coffee Break 15:30 - 16:30 Seminar M. Yamaguchi [pdf] |
16:00 - 16:30 Coffee Break 16:30 - 17:30 Seminar M. Hertzberg [pdf] |
| 13 (Mon) | 14 (Tue) | 15 (Wed) | 16 (Thu) | 17 (Fri) |
|---|---|---|---|---|
|
15:00 - 15:30 Coffee Break 15:30 - 16:30 Seminar Y. Urakawa [pdf] |
Mini-Workshop Day1 Panasonic Auditorium Banquet |
Mini-Workshop Day2 Panasonic Auditorium |
13:30 - 14:00 Coffee Break 14:00 - 15:00 Seminar K. Lozanov [pdf] |
11:00 - 11:30 Coffee Break 11:30 - 12:30 Seminar F. Torrenti [pdf] 15:30 - 16:00 Coffee Break |
I will discuss the cosmological formation, gravitational clustering, and the complex interactions of solitons (oscillons, and their non-relativistic analogs) in scalar fields. Different aspects of the results (and associated open questions) are relevant for the end of inflation, and for dynamics in axion(like) dark matter fields.
I will present some universal results regarding the non-perturbative excitation of spectator fields from a large number of stochastic and non-adiabatic particle production events in an expanding universe. I will discuss potential implications for inflation and reheating after inflation. This work was initially motivated by a surprising mathematical mapping between stochastic particle production in cosmology and current conduction in disordered wires.
We present the results of a new field-theoretic simulation of cosmological axion strings, which are eight times longer than previous ones. We have upgraded our previous simulation of physical strings in terms of the number of grids as well as the suite of analysis methods. These improvements enable us to monitor a variety of quantities characterizing the dynamics of the physical string network for the longest term ever. Our extended simulations have revealed that global strings do not evolve according to the scaling solution, but that its scaling parameter, or the number of long strings per horizon, increases logarithmically in time. In addition, we have also found that the scaling parameter shows nontrivial dependence on the breaking scale of the Peccei-Quinn symmetry.
In this talk I begin by reviewing how dark matter axions may form condensates, and how this is captured by classical field theory. I explain that such condensates are spatially localized clumps, as they are organized by gravitation and self-interactions, and they may populate the galaxy. I discuss both the ground state and finite angular momentum states. I then discuss the exotic possibility of parametric resonance of these axion clumps into electromagnetic waves, which may leave an astrophysical signature. I also discuss using ultra-light axions to resolve the core-cusp problem at the center of galaxies.
Axions predicted in string theory may have a scalar potential which has a shallower potential region than the conventional cosine potential. I first show that an axion which was located at such a shallow potential region generically undergoes a prominent resonance instability. We studied non-linear dynamics of axions caused by the resonance instability based on lattice simulation. We show that string axions in a wide mass range generate gravitational waves (GWs) with peaks at various frequencies determined by the mass scales, dubbed the GW forest. This may allow us to explore string axiverse through future multi-frequency GW observations. If time permits, I will also discuss the implication of the resonance instability on generation of cosmological magnetic field.
I will talk about our works (arXiv:1608.01213, arXiv:1710.06851, arXiv:1902.06736) in which we calculate the equation of state of the inflaton field after inflation and provide an upper bound on the duration before radiation domination by taking the nonlinear dynamics of the fragmented inflaton field into account. For the models considered, I will discuss how our work significantly reduces the uncertainty in inflationary observables. I will also consider various aspects of the linear and non-linear dynamics of the inflaton such as parametric self-resonance, the generation of scalar metric perturbations and gravitational waves.
In my talk I present results on two important resonant phenomena in the early Universe: parametric resonance and oscillons. I begin by presenting a fitting analysis of parametric resonance in typical (p)reheating scenarios, based on classical lattice simulations for a wide range of resonance parameters. I will consider all the relevant stages of the process: initial linear growth, non-linear evolution, and relaxation towards equilibrium. I will provide simple fits to the relevant time scales and energy fractions in the process. I will then consider Gravitational Wave (GW) production in these scenarios, and show parametrizations for the amplitude and frequency of peaks in the GW spectra. Finally, I will present new results on oscillon formation and evolution in inflationary hilltop models. I will study and parametrize the oscillon shapes, and present numerical estimations for their lifetime.
