scholarly journals Spontaneous symmetry breaking in lasers with periodically modulated gain and refractive index

2021 ◽  
Vol 2015 (1) ◽  
pp. 012035
Author(s):  
D Dolinina ◽  
K Staliunas ◽  
A Yulin
Keyword(s):  
Refractive Index ◽  
Symmetry Breaking ◽  
Spontaneous Symmetry Breaking ◽  
Imaginary Part ◽  
Complex Potential ◽  
Kerr Nonlinearity ◽  
Optical Systems ◽  
Coupled Modes ◽  
Potential Variation ◽  
Propagating Waves

Abstract The dynamics of light in active optical systems with periodic complex potential is considered using coupled modes approach where the field is approximated by two counter propagating waves. It is demonstrated that shifting the position of the imaginary part of the potential (effective gain) with respect to the real part of the potential (variation of the refractive index) one can control the effective gain/losses seen by the upper and the power modes. This effect can be used to control the radiation from the laser. The effect of the Kerr nonlinearity is also considered and it is shown that this can result in spontaneous symmetry breaking leading to the formation of the hybrid nonlinear states.

scholarly journals Stick-Slip model for actin-driven cell protrusions, cell polarisation and crawling

2020 ◽  
Author(s):  
Pierre Sens
Keyword(s):  
Symmetry Breaking ◽  
Spontaneous Symmetry Breaking ◽  
Biochemical Network ◽  
Cellular Mechanics ◽  
Stick Slip ◽  
Substrate Adhesion ◽  
Propagating Waves ◽  
Intracellular Forces ◽  
Cell Motion ◽  
Cytoskeleton Dynamics

Cell crawling requires the generation of intracellular forces by the cytoskeleton and their transmission to an extracellular substrate through specific adhesion molecules. Crawling cells show many features of excitable systems, such as spontaneous symmetry breaking and crawling in the absence of external cues, and periodic and propagating waves of activity. Mechanical instabilities in the active cytoskeleton network and feedback loops in the biochemical network of activators and repressors of cytoskeleton dynamics have been invoked to explain these dynamical features. Here, we show that the interplay between the dynamics of cell-substrate adhesion and linear cellular mechanics is sufficient to reproduce many non-linear dynamical patterns observed in spreading and crawling cells. Using an analytical formalism of the molecular clutch model of cell adhesion, regulated by local mechanical forces, we show that cellular traction forces exhibit a stick-slip dynamics resulting in periodic waves of protrusion/retraction and propagating waves along the cell edge. This can explain spontaneous symmetry breaking and polarisation of spreading cells, leading to steady crawling or bipedal motion, and bistability, where persistent cell motion requires a sufficiently strong transient external stimulus. The model also highlight the role of membrane tension in providing the long-range mechanical communication across the cell required for symmetry breaking.

scholarly journals Stick–slip model for actin-driven cell protrusions, cell polarization, and crawling

2020 ◽  
Vol 117 (40) ◽  
pp. 24670-24678 ◽  
Author(s):  
Pierre Sens
Keyword(s):  
Symmetry Breaking ◽  
Spontaneous Symmetry Breaking ◽  
Cell Polarization ◽  
Biochemical Network ◽  
Cellular Mechanics ◽  
Stick Slip ◽  
Nonlinear Dynamical ◽  
Substrate Adhesion ◽  
Propagating Waves ◽  
Intracellular Forces

Cell crawling requires the generation of intracellular forces by the cytoskeleton and their transmission to an extracellular substrate through specific adhesion molecules. Crawling cells show many features of excitable systems, such as spontaneous symmetry breaking and crawling in the absence of external cues, and periodic and propagating waves of activity. Mechanical instabilities in the active cytoskeleton network and feedback loops in the biochemical network of activators and repressors of cytoskeleton dynamics have been invoked to explain these dynamical features. Here, I show that the interplay between the dynamics of cell–substrate adhesion and linear cellular mechanics is sufficient to reproduce many nonlinear dynamical patterns observed in spreading and crawling cells. Using an analytical formalism of the molecular clutch model of cell adhesion, regulated by local mechanical forces, I show that cellular traction forces exhibit stick–slip dynamics resulting in periodic waves of protrusion/retraction and propagating waves along the cell edge. This can explain spontaneous symmetry breaking and polarization of spreading cells, leading to steady crawling or bipedal motion, and bistability, where persistent cell motion requires a sufficiently strong transient external stimulus. The model also highlights the role of membrane tension in providing the long-range mechanical communication across the cell required for symmetry breaking.

Spontaneous symmetry breaking of dislocation core in SrTiO3

2021 ◽  
pp. 100453
Author(s):  
Hetian Chen ◽  
Di Yi ◽  
Ben Xu ◽  
Jing Ma ◽  
Cewen Nan
Keyword(s):  
Symmetry Breaking ◽  
Spontaneous Symmetry Breaking ◽  
Dislocation Core

scholarly journals Tachyons and Solitons in Spontaneous Symmetry Breaking in the Frame of Field Theory

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1358
Author(s):  
Yiannis Contoyiannis ◽  
Michael P. Hanias ◽  
Pericles Papadopoulos ◽  
Stavros G. Stavrinides ◽  
Myron Kampitakis ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Spontaneous Symmetry Breaking ◽  
Critical Point ◽  
Universality Class ◽  
Lattice Simulation ◽  
Ginzburg Landau ◽  
Spin Lattice ◽  
Nuclear Collisions ◽  
Ising Spin ◽  
Relativistic Nuclear Collisions

This paper presents our study of the presence of the unstable critical point in spontaneous symmetry breaking (SSB) in the framework of Ginzburg–Landau (G-L) free energy. Through a 3D Ising spin lattice simulation, we found a zone of hysteresis where the unstable critical point continued to exist, despite the system having entered the broken symmetry phase. Within the hysteresis zone, the presence of the kink–antikink SSB solitons expands and, therefore, these can be observed. In scalar field theories, such as Higgs fields, the mass of this soliton inside the hysteresis zone could behave as a tachyon mass, namely as an imaginary quantity. Due to the fact that groups Ζ(2) and SU(2) belong to the same universality class, one expects that, in future experiments of ultra-relativistic nuclear collisions, in addition to the expected bosons condensations, structures of tachyon fields could appear.

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