arXiv subjects

Daniel J. H. Chung

Publications and source records attributed to Daniel J. H. Chung.

64 records · Page 4Linked to original sources

arXiv1999

Probing Planckian physics: resonant production of particles during inflation and features in the primordial power spectrum

The phenomenon of resonant production of particles {\it after} inflation has received much attention in the past few years. In a new application of resonant production of particles, we consider the effect of a resonance {\em during} inflation. We show that if the inflaton is coupled to a massive particle, resonant production of the particle during inflation modifies the evolution of the inflaton, and may leave an imprint in the form of sharp features in the primordial power spectrum. Precision measurements of microwave background anisotropies and large-scale structure surveys could be sensitive to the features, and probe the spectrum of particles as massive as the Planck scale.

hep-ph↗

arXiv1999

The MSW Effect in Quantum Field Theory

We show in detail the general relationship between the Schrödinger equation approach to calculating the MSW effect and the quantum field theoretical S-matrix approach. We show the precise form a generic neutrino propagator must have to allow a physically meaningful ``oscillation probability'' to be decoupled from neutrino production fluxes and detection cross-sections, and explicitly list the conditions---not realized in cases of current experimental interest---in which the field theory approach would be useful.

hep-ph↗

arXiv1998

WIMPZILLAS!

There are many reasons to believe the present mass density of the universe is dominated by a weakly interacting massive particle (WIMP), a fossil relic of the early universe. Theoretical ideas and experimental efforts have focused mostly on production and detection of thermal relics, with mass typically in the range a few GeV to a hundred GeV. Here, I will review scenarios for production of nonthermal dark matter. Since the masses of the nonthermal WIMPS are in the range 10^{12} to 10^{16} GeV, much larger than the mass of thermal wimpy WIMPS, they may be referred to as WIMPZILLAS. In searches for dark matter it may be well to remember that ``size does matter.''

hep-ph↗

arXiv1998

Nonthermal Supermassive Dark Matter

We discuss several cosmological production mechanisms for nonthermal supermassive dark matter and argue that dark matter may be elementary particles of mass much greater than the weak scale. Searches for dark matter should not be limited to weakly interacting particles with mass of the order of the weak scale, but should extend into the supermassive range as well.

hep-ph↗

arXiv1998

Classical inflaton field induced creation of superheavy dark matter

We calculate analytically and numerically the production of superheavy dark matter (X) when it is coupled to the inflaton field ϕwithin the context of a slow-roll m_ϕ^2 ϕ^2/2 inflationary model with coupling g^2 X^2 ϕ^2/2. We find that X particles with a mass as large as 1000 H_i, where H_i is the value of the Hubble expansion rate at the end of inflation, can be produced in sufficient abundance to be cosmologically significant today. This means that superheavy dark matter may have a mass of up to 10^{-3} Planck mass. We also derive a simple formula that can be used to estimate particle production as a result of a quantum field's interaction with a general class of homogeneous classical fields. Finally, we note that the combined effect of the inflaton field and the gravitational field on the X field causes the production to be a nonmonotonic function of g^2.

hep-ph↗

arXiv1998

Production of massive particles during reheating

What is commonly called the reheat temperature, $T_{RH}$, is not the maximum temperature obtained after inflation. The maximum temperature is, in fact, much larger than $T_{RH}$. As an application of this we consider the production of massive stable dark-matter particles of mass $M_X$ during reheating, and show that their abundance is suppressed as a power of $T_{RH}/M_X$ rather than $\exp(-M_X/T_{RH})$. We find that particles of mass as large as $2\times 10^3$ times the reheat temperature may be produced in interesting abundance. In addition to dark matter, our analysis is relevant for baryogenesis if the baryon asymmetry is produced by the baryon (or lepton) number violating decays of superheavy bosons, and also for relic ultra-high energy cosmic rays if decays of superheavy particles are responsible for the highest energy cosmic rays.

hep-ph↗

arXiv1998

Superheavy Dark Matter

If there exist fields of mass of the order of $10^{13}$ GeV and large field inflation occurs, their interaction with classical gravitation will generate enough particles to give the universe critical density today regardless of their nongravitational coupling. This is mainly a summary of the work hep-ph/9802238.

hep-ph↗

arXiv1998

Superheavy dark matter

We show that in large-field inflationary scenarios, superheavy (many orders of magnitude larger than the weak scale) dark matter will be produced in cosmologically interesting quantities if superheavy stable particles exist in the mass spectrum. We show that these particles may be produced naturally during the transition from the inflationary phase to either a matter-dominated or radiation-dominated phase as a result of the expansion of the background spacetime acting on vacuum quantum fluctuations of the dark matter field. We find that as long as there are stable particles whose mass is of the order of the inflaton mass (presumably around $10^{13}$GeV), they will be produced in sufficient abundance to give $Ω_0 =1$ quite independently of any details of the non-gravitational interactions of the dark-matter field.

hep-ph↗

arXiv1997

Are ultrahigh energy cosmic rays signals of supersymmetry?

We investigate the possibility that cosmic rays of energy larger than the Greisen-Zatsepin-Kuzmin cutoff are not nucleons, but a new stable, massive, hadron that appears in many extensions of the standard model. We focus primarily on the S^0, a uds-gluino bound state. The range of the S^0 through the cosmic background radiation is significantly longer than the range of nucleons, and therefore can originate from sources at cosmoglogical distances.

astro-ph↗

arXiv1997

On the relic abundance of light photinos

We solve the coupled Boltzmann equation for the system of light photinos interacting with pions and $R^0$'s (the gluon-gluino bound state) to determine the relic abundance of light photinos in the light gaugino scenario. Cosmology bounds the ratio r of the R^0 mass to the photino mass to be less than about 1.8. We also use a model Lagrangian embodying crossing symmetry between the $R^0 \leftrightarrow \photino ππ$ and $R^0 π\leftrightarrow \photino π$ reactions to identify cosmologically favored regions of $R^0$ lifetime as a function of $R^0$ and photino masses.

astro-ph↗