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Considering a constant dissipative coefficient $\mathrm{\Gamma }$, the pre-inflation dynamical behaviors of warm inflation in the loop quantum cosmology scenario are discussed. We consider three sets of initial conditions. The evolution of the background can always be divided into three phases, namely super-inflation, damping, and slow-roll inflation phases, with the duration of each phase depending on the initial conditions. As an example, we compare the background evolution between $\mathrm{\Gamma }=0.001m_{\mathrm{\text{Pl}}}$ and $\mathrm{\Gamma }=0$ under special initial conditions and find that there is no slow-roll inflation phase for $\mathrm{\Gamma }=0$ while the number of e-folds is about 60.209 for $\mathrm{\Gamma }=0.001m_{\mathrm{\text{Pl}}}$.

Plasma instabilities are responsible not only for the onset and mediation of collisionless shocks but also for the associated acceleration of particles. We have investigated particle acceleration and shock structure associated with an unmagnetized relativistic electron-positron jet propagating into an unmagnetized electron-positron plasma. Cold jet electrons are thermalized and slowed while the ambient electrons are swept up to create a partially developed hydrodynamic-like shock structure. In the leading shock, electron density increases by a factor of about 3.5 in the simulation frame. Strong electromagnetic fields are generated in the trailing shock and provide an emission site. These magnetic fields contribute to the electrons transverse deflection and, more generally, relativistic acceleration behind the shock. We have calculated, self-consistently, the radiation from electrons accelerated in the turbulent magnetic fields. We found that the synthetic spectra depend on the Lorentz factor of the jet, its thermal temperature and strength of the generated magnetic fields. The properties of the radiation may be important for understanding the complex time evolution and/or spectral structure in gamma-ray bursts, relativistic jets in general, and supernova remnants.

We have investigated the generation of magnetic fields associated with velocity shear between an unmagnetized relativistic (core) jet and an unmagnetized sheath plasma by the kinetic Kelvin-Helmholtz instability for different mass ratios (m_i/m_e = 1, 20, and 1836) and different jet Lorentz factors. We found that electron-positron cases have alternating magnetic fields instead of the DC magnetic fields found in electron-ion cases. We have also investigated particle acceleration and shock structure associated with an unmagnetized relativistic jet propagating into an unmagnetized plasma for electron-positron and electron-ion plasmas. Strong magnetic fields generated in the trailing shock lead to transverse deflection and acceleration of the electrons. We have self-consistently calculated the radiation from the electrons accelerated in the turbulent magnetic fields for different jet Lorentz factors. We find that the synthetic spectra depend on the bulk Lorentz factor of the jet, the jet temperature, and the strength of the magnetic fields generated in the shock.

The Linac Coherent Light Source II (LCLS-II) will be a hard X-ray Free Electron Laser whose linac can deliver a 1.2 MW CW electron beam with bunch rates up to 1 MHz. To efficiently generate such a high power beam, Super-Conducting Radio-Frequency (SCRF) cavities will be installed in the upstream portion of the existing 3 km Linac at the SLAC National Accelerator Laboratory. The 9-cell niobium cavities will be cooled at 2K inside 35 cryomodules, each containing a string of eight of those cavities followed by a quadrupole. The strong electromagnetic fields in the SCRF cavities will extract electrons from the cavity walls that may be accelerated. Most such dark current will be deposited locally, although some electrons may reach several neighboring cryomodules, gaining substantial energy before they hit a collimator or other aperture. The power deposited by the field emitted electrons and the associated showers may pose radiation and machine protection issues at the cryomodules and also in other areas of the accelerator. Simulation of these effects is therefore crucial for the design of the machine. The in-house code Track3P was used to simulate field emitted electrons from the LCLS-II cavities, and a sophisticated 3D model of the cryomodules including all cavities was written to transport radiation with the Fluka Monte Carlo code, which was linked to Track3P through custom-made routines. This setup was used to compute power deposition in components, prompt and residual radiation fields, and radioisotope inventories.

A brief overview of the technology applications with significant societal benefit that have their origins in nuclear and particle physics research is presented. It is shown through representative examples that applications of nuclear physics can be classified into two basic areas: 1) applying the results of experimental nuclear physics and 2) applying the tools of experimental nuclear physics. Examples of the application of the tools of experimental nuclear and particle physics research are provided in the fields of accelerator and detector based technologies namely synchrotron light sources, nuclear medicine, ion implantation and radiation therapy.

Fascinated people from the dawn of history, gravity is not understood, still. Here, we suggest that gravity is a result of a process in the material: (1) Gravitational photons are produced by all atoms that exist in nonzero temperature and or interact with radiation, similar to black body radiation. (2) Then, these photons move in the material. The electromagnetic properties of the gravitational photons and the structure of the object cause the photons’ trajectories to bend. (3) Such trajectories generate a force pointing to the center of mass of the object, due to the circular motion and the electromagnetic properties of the gravitational photons. These trajectories are radiated outwards, as in antennae, although at a much slower rate, due to that force. So basically gravity is a simple process (as black body radiation), just a sort of generalized radiation pressure due to the process of gravity in the material, resulting in antenna like radiation emission, of these unique electromagnetic waves that are pressed towards the radiating object center of mass during their circular motion in the object. Going beyond the dynamical model, we identify various possible forms of the gravitational photons, and their general invariant properties. With this theory, we (1) explain various unexplained phenomena that are related to gravity, yet also suggest (2) method and apparatus for gravity shielding, and (3) gravitational radiation energy cultivation. This theory can form the missing part for the “theory of everything”.

Free massless fields of any spin in flat D-dimensional spacetime propagate at the speed of light. But the retarded fields produced by the corresponding point-like moving sources share this property only for even D. Since the Green’s functions of the d’Alembert equation are localized on the light cone in even-dimensional spacetime, but not in odd dimensions, extraction of the emitted part of the retarded field in odd D requires some care. We consider the wave equations for spins 0, 1, and 2 in five-dimensional spacetime and analyze the fall-off conditions for the retarded fields at large distances. It is shown that the farthest part of the field contains a component propagating at the speed of light, while the non-derivative terms propagate with all velocities up to that of light. The generated radiation will contain a radiation tail corresponding to the complete prehistory of the source’s motion preceding the retarded moment of time. We also demonstrate that dividing the Green’s function into a part localized on the light cone and another part that is not zero inside the light cone gives separately the divergent terms in the Coulomb field of a point source. Their sum, however, is finite and corresponds to the usual power-law behaviour.

The standard ΛCDM cosmological model now seems to face some puzzles. One of the most serious problems is the so-called Hubble tension; the values of the Hubble constant H₀ obtained by local measurements look inconsistent with that inferred from Cosmic Microwave Background (CMB). Although introducing extra energy components such as the extra radiation or Early Dark Energy appears to be promising, such extra components could alter the abundance of light elements synthesized by Big Bang Nucleosynthesis (BBN). We perform a Monte Carlo simulation to evaluate the effect of those extra component scenarios to solve the Hubble tension on the BBN prediction.

I discuss the progress in the numerical modeling of accretion flows made possible after solving the general relativistic radiation-hydrodynamics equations through the moment formalism and with Godunov-type methods. I first present the necessary numerical tools for coping with the stiffness of the source terms in the equations and for treating the intermediate regime between the optically thick and the optically thin. Then, I show some applications to spherical accretion and to supersonic Bondi-Hoyle accretion onto a black hole, discussing its astrophysical relevance.

Two radiation regimes are considered. The first one is provided by electrons moving in a magnetic field in circles with non-relativistic velocity (Cyclotron radiation). The second one is provided by electrons moving in a magnetic field on a helix with ultra-relativistic longitudinal and non-relativistic transverse velocity components. The applicability of these models is considered by the example of the object Hercules X-1. The test based on polarization observations is suggested to distinguish between the cyclotron and relativistic dipole origin of features observed in X-ray spectra of X-ray sources.