Cosmological transitions with changes in the signature of the metric

Abstract

PACS. 61.20.Ja -Computer simulation of liquid structure. PACS. 61.72.Bb -Theories and models of crystal defects. PACS. 87.16.Dg -Membranes, bilayers, and vesicles.Abstract. -The freezing transition of a network model for flexible tensionless membranes fluctuating about a planar reference state is investigated by Monte Carlo simulations and scaling arguments. The bond-orientational order parameter susceptibility is analyzed for three values of the bending rigidity κ, and it is found that for sufficiently large κ the low-temperature hexatic phase melts via a universal Kosterlitz-Thouless transition. These results are consistent with recent theoretical predictions that the crumpled-to-crinkled transition occurs via disclination melting for all bending rigidities and tether lengths. However, our simulations provide evidence that the transition becomes first order at very low bending rigidity.c EDP Sciences

Inflation, de Sitter landscape and super-Higgs effect

“…Usually this happened automatically for the field a, whereas the field S often required stabilization, which could be achieved e.g. by the terms (SS) 2 The generality of the choice of the function f (Φ) allows to fit any possible set of the inflationary parameters n s and r. As a next step, one should try to describe dark energy/cosmological constant, and also supersymmetry breaking.…”

“…Our general models have a nice feature stressed also by Dall'Agata and Zwirner [30], that the models at the minimum of the potential break supersymmetry spontaneously only in the direction of the nilpotent goldstino multiplet. 2 Our class of superpotentials depends on two different functions which allow to construct 1 The relation between the nilpotent superfields and VA models has been recognized long time ago [33][34][35][36]. However, the relevant chiral superfields in addition to the nilpotency condition S 2 (x, θ) = 0 were also required to satisfy an equation of motion.…”

“…Therefore in cosmological applications we are using the off-shell nilpotent superfields [37]. 2 The superpotential in [30] is given by W = f (Φ) (1 + √ 3 S). A choice of √ 3 is, of course, a well-known fine-tuning designed to produce V0 = 0.…”

“…(2.7) in [27]. Since the auxiliary field F S of the nilpotent multiplet appears in negative powers in fermion-dependent terms such as 2 , the elimination of F S will lead to a complicated fermionic part of the classical supergravity action. The bosonic part remains simple, but the fermionic one is complicated.…”

“…The only presently available explanation of the smallness of V 0 is given by the anthropic argument [1][2][3][4][5] in the string theory landscape with enormously large set of dS and AdS vacua with different values of V 0 [6][7][8][9][10][11][12]. Supersymmetry provides a certain quality control in the inflationary model construction, and helps to stabilize string theory vacua.…”