17751676
The phase structure of the early universe in the minimal SU(5) grand unified theory
Abstract Using the most general, gauge invariant and renormalizable Higgs potential which avoids domain walls, we study the possible phases that can appear at high temperatures in the minimal SU(5) grand unified theory. We emphasize the important role of the fundamental representation of Higgs field for the phase structure at temperatures of 10 14 GeV.
122674516
Point splitting regularization in a supersymmetric gauge field theory
Abstract Point splitting regularization is discussed in a supersymmetric Yang-Mills field theory. A supersymmetry and gauge invariant point-split supercurrent operator, along with the point-split lagrangian density, is constructed. A superconformal anomaly is computed.
118191225
Cosmological Consequences of Grand Unified Theories
122337528
Cosmological consequences of a hierarchical supersymmetric model
Abstract Unusual finite-temperature behavior of Witten's supersymmetric model is discussed. A high-temperature phase persists to the weak-interaction scale. Initial monopole density can be strongly suppressed and production of heavy particles is inhibited. Difficulties with baryon generation are suggested.
122607008
Goldstone and pseudo-Goldstone bosons in unified gauge-field models
124346945
Fluctuations in the New Inflationary Universe
This invention relates to novel rolling type athletic apparatus taking advantage of the characteristic of stilts which comprises a pair of vertical rods each consisting of two pipces telescopically connected to each other. The upper end of each vertical rod is bent to form a handle. Each rod is provided at its lower end with a wheel having a brake and a one-way clutch. A step is mounted on the upper portion of the wheel.
118471930
Equilateral non-Gaussianity from heavy fields
The effect of self-interactions of heavy scalar fields during inflation on the primordial non-Gaussianity is studied. We take a specific constant-turn quasi-single field inflation as an example. We derive an effective theory with emphasis on non-linear self-interactions of heavy fields and calculate the corresponding non-Gaussianity, which is of equilateral type and can be as relevant as those computed previously in the literature. We also derive the non-Gaussianity by directly using the in-in formalism, and verify the equivalence of these two approaches.
118390460
1/R correction to gravity in the early universe
To explain the accelerated expansion of the late universe, the 1/R correction to Einstein gravity is usually considered, where R is the Ricci scalar. This correction term, if stable, is generally believed to be negligible during inflation. However, if the 1/R term is inflaton dependent, it will dramatically change the story of inflation. The entropy perturbation will naturally appear and drive the evolution of curvature perturbation outside the Hubble horizon. In a large class of models, the entropy perturbation can be made nearly scale invariant. In Einstein gravity the single-field inflation with a quartic potential has been ruled out by recent observations, but it revives when the 1/R term is turned on. The evolution of non-Gaussianities on a large scale are also studied and applied to inflation with 1/R correction. In some specific models, a large non-Gaussianity can be naturally generated outside the horizon. A recent study ruled out almost all f(R) models during the matter-dominated phase. Taking this into consideration, we are left with a limited class of model which recovers the Einstein gravity soon after reheating.
119238882
On the possibility of blue tensor spectrum within single field inflation
We present a series of theoretical constraints on the potentially viable inflation models that might yield a blue spectrum for primordial tensor perturbations. By performing a detailed dynamical analysis we show that, while there exists such possibility, the corresponding phase space is strongly bounded. Our result implies that, in order to achieve a blue tilt for inflationary tensor perturbations, one may either construct a non-canonical inflation model delicately, or study the generation of primordial tensor modes beyond the standard scenario of single slow-roll field.
117214043
Cosmological perturbations in inflation with multiple sound speeds
Abstract We study a multi-field inflationary theory with separable Lagrangian, which has different speed of sound for each field. We find that the fields always coupled at perturbative level through gravitational interaction. We show that if the coupling terms among the perturbation fields are weak enough, these fields can be treated as a combination of decoupled fields, which are similar to normal modes in coupled oscillation. By virtue of such fields, the curvature perturbation at horizon crossing can be calculated up to the leading order of slow-variation parameters via δ N formalism. Explicitly, we consider a model of multi-speed DBI inflation, and calculate the power spectrum in detail. The result depends on the ratio of different speeds of sound, and shows an apparent amplification when the ratio deviates from unity.
118608368
Scale invariant power spectrum in Hořava-Lifshitz cosmology without matter
In this paper we investigate the physical implications of the dynamical scalar mode in pure Hořava-Lifshitz gravity on cosmology. We find that it can produce a scale-invariant power spectrum in UV era if the detailed balance condition on the action is relaxed. This indicates that the physical scalar mode may seed the large scale structure and Hořava-Lifshitz cosmology could be a qualified alternative to inflationary scenario.