Effective Minkowski to Euclidean signature change of the magnon BEC pseudo-Goldstone mode in polar He, "Письма в Журнал экспериментальной и теоретической физики"

2017 ◽  
pp. 220-221 ◽  
Author(s):  
J. Nissinen ◽  
G. E. Volovik
Keyword(s):  
Goldstone Mode ◽  
Signature Change ◽  
Euclidean Signature

scholarly journals Classical Signature Change in the Black Hole Topology

1997 ◽  
Vol 06 (02) ◽  
pp. 211-238 ◽  
Author(s):  
Chariles Hellaby ◽  
Ariel Sumeruk ◽  
G. F. R. Ellis
Keyword(s):  
Black Holes ◽  
Big Bang ◽  
Recent Proposal ◽  
Signature Change ◽  
Lorentzian Signature ◽  
Free Region ◽  
Euclidean Region ◽  
Two Universes ◽  
The Big Bang ◽  
Euclidean Signature

Investigations of classical signature change have generally envisaged applications to cosmological models, usually a Friedmann–Lemaître–Robertson–Walker model. The purpose has been to avoid the inevitable singularity of models with purely Lorentzian signature, replacing the neighbourhood of the big bang with an initial, singularity free region of Euclidean signature, and a signature change. We here show that signature change can also avoid the singularity of gravitational collapse. We investigate the process of re-birth of Schwarzschild type black holes, modelling it as a double signature change, joining two universes of Lorentzian signature through a Euclidean region which provides a "bounce". We show that this process is viable both with and without matter present, but realistic models — which have the signature change surfaces hidden inside the horizons — require nonzero density. In fact the most realistic models are those that start as a finite cloud of collapsing matter, surrounded by vacuum. We consider how geodesics may be matched across a signature change surface, and conclude that the particle "masses" must jump in value. This scenario may be relevant to Smolin's recent proposal that a form of natural selection operates on the level of universes, which favours the type of universe we live in.

scholarly journals Distributions in CFT. Part II. Minkowski space

2021 ◽  
Vol 2021 (8) ◽  
Author(s):  
Petr Kravchuk ◽  
Jiaxin Qiao ◽  
Slava Rychkov
Keyword(s):  
Minkowski Space ◽  
Statistical Physics ◽  
Minimal Set ◽  
Local Commutativity ◽  
Classic Result ◽  
Lorentzian Signature ◽  
Open Question ◽  
Wightman Axioms ◽  
Euclidean Signature ◽  
3D Ising Model

Abstract CFTs in Euclidean signature satisfy well-accepted rules, such as the convergent Euclidean OPE. It is nowadays common to assume that CFT correlators exist and have various properties also in Lorentzian signature. Some of these properties may represent extra assumptions, and it is an open question if they hold for familiar statistical-physics CFTs such as the critical 3d Ising model. Here we consider Wightman 4-point functions of scalar primaries in Lorentzian signature. We derive a minimal set of their properties solely from the Euclidean unitary CFT axioms, without using extra assumptions. We establish all Wightman axioms (temperedness, spectral property, local commutativity, clustering), Lorentzian conformal invariance, and distributional convergence of the s-channel Lorentzian OPE. This is done constructively, by analytically continuing the 4-point functions using the s-channel OPE expansion in the radial cross-ratios ρ, $$ \overline{\rho} $$ ρ ¯ . We prove a key fact that |ρ|, $$ \left|\overline{\rho}\right| $$ ρ ¯ < 1 inside the forward tube, and set bounds on how fast |ρ|, $$ \left|\overline{\rho}\right| $$ ρ ¯ may tend to 1 when approaching the Minkowski space.We also provide a guide to the axiomatic QFT literature for the modern CFT audience. We review the Wightman and Osterwalder-Schrader (OS) axioms for Lorentzian and Euclidean QFTs, and the celebrated OS theorem connecting them. We also review a classic result of Mack about the distributional OPE convergence. Some of the classic arguments turn out useful in our setup. Others fall short of our needs due to Lorentzian assumptions (Mack) or unverifiable Euclidean assumptions (OS theorem).

Signature change in p-adic and noncommutative FRW cosmology

2014 ◽  
Vol 29 (27) ◽  
pp. 1450155 ◽  
Author(s):  
Goran S. Djordjevic ◽  
Ljubisa Nesic ◽  
Darko Radovancevic
Keyword(s):  
Loop Quantum Gravity ◽  
Initial Conditions ◽  
Planck Scale ◽  
The Other ◽  
Frw Cosmology ◽  
Signature Change ◽  
Discrete Nature ◽  
Frw Metric ◽  
The Universe ◽  
Friedmann Robertson Walker

The significant matter for the construction of the so-called no-boundary proposal is the assumption of signature transition, which has been a way to deal with the problem of initial conditions of the universe. On the other hand, results of Loop Quantum Gravity indicate that the signature change is related to the discrete nature of space at the Planck scale. Motivated by possibility of non-Archimedean and/or noncommutative structure of space–time at the Planck scale, in this work we consider the classical, p-adic and (spatial) noncommutative form of a cosmological model with Friedmann–Robertson–Walker (FRW) metric coupled with a self-interacting scalar field.

scholarly journals EFFECTIVE FIELD THEORY OF IDEAL-FLUID HYDRODYNAMICS

1996 ◽  
Vol 10 (21) ◽  
pp. 999-1010 ◽  
Author(s):  
ADRIAAN M.J. SCHAKEL
Keyword(s):  
Field Theory ◽  
Effective Field Theory ◽  
Effective Field ◽  
Effective Theory ◽  
Goldstone Mode ◽  
Hydrodynamic Equations ◽  
Standard Description ◽  
Spontaneous Breakdown ◽  
Sound Mode ◽  
Fluid Hydrodynamics

Starting from a standard description of an ideal, isentropic fluid, we derive the effective theory governing a gapless non-relativistic mode — the sound mode. The theory, which is dictated by the requirement of Galilei invariance, entails the entire set of hydrodynamic equations. The gaplessness of the sound mode is explained by identifying it as the Goldstone mode associated with the spontaneous breakdown of Galilei invariance. Differences with a superfluid are pointed out.

EFFECT OF CELL THICKNESS ON THE DIELECTRIC RELAXATION PROCESSES IN FERROELECTRIC LIQUID CRYSTALS

2008 ◽  
Vol 22 (14) ◽  
pp. 2263-2273 ◽  
Author(s):  
RAJBIR SINGH ◽  
K. K. RAINA
Keyword(s):  
Liquid Crystal ◽  
Dielectric Relaxation ◽  
Dielectric Strength ◽  
Relaxation Processes ◽  
Goldstone Mode ◽  
Ferroelectric Liquid Crystal ◽  
Dielectric Relaxation Spectroscopy ◽  
Dielectric Parameters ◽  
Liquid Crystal Material ◽  
Cell Thickness

Dielectric relaxation spectroscopy in the frequency range 50 Hz to 1 MHz has been carried out in a room temperature ferroelectric liquid crystal mixture in the SmC*, SmA and N* phases in cells of different thickness. The relaxation frequency fr, distribution parameter α and dielectric strength δ∊ have been evaluated. Goldstone mode, domain mode and soft mode have been observed. It is found that the cell thickness has a significant effect on the dielectric parameters of the ferroelectric liquid crystal material. The results have been discussed.

Sign in / Sign up

Export Citation Format

Share Document