121291742
A six-dimensional cosmology solution with GUT and monopole-induced spontaneous compactification
In this paper, the authors present a cosmological solution of a six-dimensional Einstein-gauge unification theory to which is added a matter term. This exact solution appears that cosmology of the very early universe may differ considerably from the usually contemplated scenarios.
117665288
Instantons in grand unification
SummaryA class of instantons in four-dimensional Euclidean grand unification is discussed. These solutions in the classical limit have nonzero Lagrangian density at only one single point. These instantons can generate proton decay processes, whose rate has an extremely feeble effect in theSU5 model. However, it can be observable in unification with technifermions that embedded instantons induce technifermions decay to ordinary fermion. We also consider the instantons in aSO10 model.RiassuntoSi discute una classe di instantoni nella grande unificazione euclidea a quattro dimensioni. Queste soluzioni nel limite classico hanno densità lagrangiana non nulla solo in un singolo punto. Questi istantoni possono generare processi di decadimento protonico, il cui valore ha un effetto molto debole nel modelloSU5. Tuttavia, si può osservare che, nella unificazione con i tecnifermioni, gli istantoni inclusi inducono decadimenti dei tecnifermioni a fermioni ordinari. Si considerano anche gli istantoni in un modelloSO10.РезюмеОбсуждается класс инстантонов в четырехмерном эвклидовом великом объединении. Эти решения в классическом пределе имеют ненулевую плотность Лагранжиана только в одной изолированной точке. Эти инстантоны могут генерировать процессы распада протона. Интенсивность этих процессов представляет чрезвычайно малый эффект в моделиSU5. Однако, этот процесс может быть наблюдаем при объединении с технифермионом, когда внедренный инстантон индуцирует распад технифермионов в обыкновенные фермионы. Мы также рассматриваем инстантоны в моделиSO10.
124596353
DOES THE RUBAKOV EFFECT EXIST IN AN SU(2) MODEL
In an spontaneously broken gauge theory with a Higgs triplet, the mass effect of an isospin 1/2 fermion on the fermion-monopole bound states is discussed. It is shown that when the direct coupling between fermion and Higgs field approaches zero, but the Dirac mass remains finiteness, the necessary condition of the fermion-monopole bound state cannot be satisfied. This result means that the Rubakov effect is absent for monopole because of the Dirac mass.
121018905
A class of generalized monopole solutions in Kaluza-Klein theories
Abstract We present a new class of generalized monopole solutions in Kaluza-Klein theories. Both the Gross-Perry-Sorkin solution and the Bais-Batenburg solutions are contained as special cases of the general solutions.
120212512
The mass matrix of neutral fermions and application in some SUSY E6-GUT
The fermion mass spectrum remains one of the outstanding problems of grand unification. The authors discuss the mass matrix of neutral fermions, which arises in three SUSY E6-breaking patterns by including the contributions of the five-dimensional superpotential terms. The solar neutrino puzzle is solved in the breakdown through SU3C*SU3L*SU3R. The model is shown to lead naturally to large oscillations of the doublet neutrino into a sterile fermion leading to the possibility of substantial depletion of the solar electron neutrino flux.
118721470
On the SO(10) instanton
A class of instantons in a four-dimensional Euclidean SO(10) model of grand unification is discussed. These solutions in the classical limit have nonzero Lagrangian density at only one single point. These instantons can generate baryon-number violation processes with rates which could be observable in the not too distant future.
10026539
Constraining anisotropy of the universe from different groups of type-Ia supernovae
Recently released Planck data and other astronomical observations show that the universe may be anisotropic on large scales. Inspired by this, anisotropic cosmological models have been proposed. We note that the Finsler–Randers spacetime provides an appropriate framework for the anisotropic cosmology. By adding an arbitrary 1-form to the Friedmann–Robertson–Walker line element, a privileged axis in the universe is picked out. The distance–redshift relation is modified to be direction-dependent. We wish that the anisotropic cosmological model may be tested crossly by independent observations. Type-Ia supernovae (SNe Ia) calibrated from four different light curve fitters are used to constrain the possible anisotropy of the universe. The magnitudes of anisotropy are all between 2–5 %, but the systematic uncertainty cannot be excluded. The directions of the privileged axis seem to differ from each other. The statistical significance is not high enough to make a convincing conclusion. Nevertheless, the $$1\sigma $$1σ contours in the $$(l,b)$$(l,b) plane obtained from four groups of SNe Ia have an overlap, centering at $$(l,b)\approx (170^{\circ }, 0^{\circ })$$(l,b)≈(170∘,0∘). Monte Carlo simulation shows that the anisotropy is unlikely to be caused by the selection effect.
118637791
Topological orbital ladders
Synthetic quantum orbital materials, such as the recent double-well optical lattices loaded with s and p orbital atoms [1, 2], open an avenue to exploit symmetries beyond natural crystals. Exotic superfluid states were reported for bosons. Here, we unveil a topological phase of interacting fermions on a two-leg ladder of unequal parity orbitals, derived from the experimentally realized double-well lattices by dimension reduction. Z2 topological invariant originates simply from the staggered phases of sp-orbital quantum tunneling, requiring none of the previously known mechanisms such as spin-orbit coupling or artificial gauge field. Another unique feature is that upon crossing over to two dimensions with coupled ladders, the edge modes from each ladder form a parity-protected flat band at zero energy, opening the route to strongly correlated states controlled by interactions. Experimental signatures are found in density correlations and phase transitions to trivial band and Mott insulators. The uneven double-well potential formed by laser light has been developed into a powerful tool for quantum gases by numerous groups [1–6]. For instance, controls of atoms on the sand p-orbitals of the checkerboard [1] and hexagonal [6] optical lattices have been demonstrated, and correlation between these orbitals tends to give exotic quantum states [6, 7]. Motivated by these developments, we consider a lattice of uneven double-wells where fermionic atoms are loaded up to the sand porbital levels of the shallow and deep wells respectively, as shown in Fig. 1. The spatial symmetry of the orbital wave function dictates the complex hopping amplitudes between nearby sites. Under certain circumstances, as for the uneven double wells, the orbital hopping pattern is sufficient for producing topologically nontrivial band structures [8]. We will first focus on a one-dimensional ladder system illustrated in Fig. 1b and 1c. This corresponds to the quasi-one dimensional limit of a standard double-well optical lattice, with the optical potential given by
119312663
Unification of Dark Matter and Dark Energy in a Modified Entropic Force Model
In Verlinde's entropic force scenario of gravity, Newton's laws and Einstein equations can be obtained from the first principles and general assumptions. However, the equipartition law of energy is invalid at very low temperatures. We show clearly that the threshold of the equipartition law of energy is related with horizon of the universe. Thus, a one-dimensional Debye (ODD) model in the direction of radius of the modified entropic force (MEF) may be suitable in description of the accelerated expanding universe. We present a Friedmann cosmic dynamical model in the ODD-MEF framework. We examine carefully constraints on the ODD-MEF model from the Union2 compilation of the Supernova Cosmology Project (SCP) collaboration, the data from the observation of the large-scale structure (LSS) and the cosmic microwave background (CMB), i.e. SNe Ia+LSS+CMB. The combined numerical analysis gives the best-fit value of the model parameters zeta similar or equal to 10(-9) and Omega(m0) = 0.224, with chi(2)(min) = 591.156. The corresponding age of the universe agrees with the result of D. Spergel et al. [J.M. Bardeen, B. Carter, and S.W. Hawking, Commun. Math. Phys. 31 (1973) 161] at 95% confidence level. The numerical result also yields an accelerated expanding universe without invoking any kind of dark energy. Taking zeta( 2 pi omega(D)/H-0) as a running parameter associated with the structure scale r, we obtain a possible unified scenario of the asymptotic flatness of the radial velocity dispersion of spiral galaxies, the accelerated expanding universe and the Pioneer 10/11 anomaly in the entropic force framework of Verlinde.
118432739
An inflationary scenario taking into account of possible dark energy effects in the early universe
We investigate the possible effect of cosmological-constant type dark energy during the inflation period of the early universe. This is accommodated by a new dispersion relation in de Sitter space. The modified inflation model of a minimally coupled scalar field is still able to yield an observation-compatible scale-invariant primordial spectrum, simultaneously having the potential to generate a spectrum with lower power at large scales. A qualitative match to the WMAP 7-year data is presented. We obtain an ΩΛ of the same order of that in the Λ-CDM model. Possible relations between the de Sitter scenario and Doubly Special Relativity (DSR) are also discussed.
118391554
A matter dominated navigation Universe in accordance with the Type Ia supernova data
We investigate a matter dominated navigation cosmological model. The influence of a possible drift (wind) in the navigation cosmological model makes the spacetime geometry change from Riemannian to Finslerian. The evolution of the Finslerian Universe is governed by the same gravitational field equation with the familiar Friedmann-Robertson-Walker one. However, the change of space geometry from Riemannian to Finslerian supplies us a new relation between the luminosity distant and redshift. It is shown that the Hubble diagram based on this new relation could account for the observations on distant Type Ia supernovae.