Emergent particles of de Sitter universe: thermal interpretation of the stochastic formalism and beyond

A thermal interpretation of the stochastic formalism of a slow-rolling scalar field in a de Sitter (dS) universe is given. By introducing a notion of emergent particles and a dual description of scalar fields, we show that the stochastic evolution of the infrared part of the field is equivalent to the Brownian motion in an abstract space filled with a heat bath of massless particles. The 1st slow-roll condition and the Hubble expansion are also reinterpreted in the abstract space as the speed of light and a transfer of conserved energy, respectively. Inspired by this, we sketch the quantum emergent particles, which may realize the Hubble expansion by an exponential particle production. This gives another meaning of dS entropy as entropy per Hubble volume in the global dS universe.Comment: 15 pages, 3 figure

The measurement of decoupled payments' effects on U.S. agricultural production

The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file viewed on (February 27, 2007)Vita.Thesis (Ph.D.) University of Missouri-Columbia 2006.In the current WTO negotiations, the developing and the developed countries take an opposite view regarding the criteria for green box subsidies supposed to be decoupled from current production levels and prices. This study investigates whether U.S. PFC and direct payment subsidies are truly decoupled from production or not by modeling the farmers' risk attitudes in a non-structural approach and estimating the effect of decoupled payments on production by the change in risk attitudes. The results show that farmers' risk attitudes are mostly risk loving and change over time, which is different from other studies. The results also show that only the amount of money matters in determining risk attitude. The effect of decoupled payments is not only statistically insignificant on corn and soybean acreage but also very small in magnitude.Includes bibliographical reference

Hubble Selection of the Weak Scale from QCD Quantum Phase Transition

If the strange quark were lighter, QCD phase transition could have been first order. Is this near-criticality just a coincidence? We show that this can explain the weak scale criticality through cosmological selection. We first explore quantum critical points of $N_f=3$ QCD, parameterized by the Higgs vev $v_h$ at $T=0$, and show that they can be attractors for the quantum-dominated evolution of $v_h$ during eternal inflation -- Hubble selection. This results in the sharply localized weak scale which is critical, not to the cross-over at zero, but to the quantum transition at ${\sim}\Lambda_{\rm QCD}$. It presents a wishful account of scale hierarchies, using quantum cosmology and near-criticality of SM.Comment: 10 pages, 5 figure

Hybridization and Decay of Magnetic Excitations in two-dimensional Triangular Lattice Antiferromagnets

Elementary quasiparticles in solids such as phonons and magnons occasionally have nontrivial interactions between them, as well as among themselves. As a result, their energy eigenvalues are renormalized, the quasiparticles spontaneously decay into a multi-particle continuum state, or they are hybridized with each other when their energies are close. As discussed in this review, such anomalous features can appear dominantly in quantum magnets but are not, a priori, negligible for magnetic systems with larger spin values and noncollinear magnetic structures. We review the unconventional magnetic excitations in two-dimensional triangular lattice antiferromagnets and discuss their implications on related issues.Comment: 18 pages, 9 figure

PBH Formation from Overdensities in Delayed Vacuum Transitions

Primordial black hole (PBH) formation from first order phase transitions combines two prevalent elements of Beyond the Standard Model physics with wide-ranging consequences. We elaborate on a recently proposed scenario in which inhomogeneities in vacuum energy decay seed the overdensities that collapse to primordial black holes. In this scenario, the PBH mass is determined by the Hubble mass as in conventional formation scenarios, while its number density is determined by the nucleation dynamics of the first-order phase transition. We present a detailed study of the formation probability including some analytical treatments. In addition, we generate populations in the open mass window as well as for the HSC and OGLE candidate microlensing events. This mechanism inevitably creates PBHs in generic first order phase transitions, with significant populations produced in slow and moderately strong phase transitions.Comment: 19 pages, 5 figure

Regurgitated Dark Matter

We present a new paradigm for the production of the dark matter (DM) relic abundance based on the evaporation of early Universe primordial black holes (PBHs) themselves formed from DM particles. We consider a minimal model of the dark sector in which a first-order phase transition results in the formation of Fermiball remnants that collapse to PBHs, which then emit DM particles. We show that the regurgitated DM scenario allows for DM to be either fermions or scalars in the mass range $\sim1$ GeV $- \,10^{16}$ GeV, thereby unlocking parameter space considered excluded.Comment: 10 pages, 2 figure