# phys: trace the birth and evolution of a quasiparticle entity

<< The idea of quasiparticles was first introduced in the 1930s by physicist Lev Landau, who was trying to gain a better understanding of complex quantum systems. >>

<< Over the past decades, physicists worldwide have been trying to gain a better understanding of non-equilibrium dynamics in quantum many-body systems. Some studies investigated what are known as quasiparticles, disturbances or entities in physical systems that exhibit behavior similar to that of particles. >>

In this study AA << observed three distinct regimes of impurity evolution marked by dynamic transitions. These regimes then link initial few-body and later many-body physical dynamics. >>

Ingrid Fadelli. Observing the birth of a quasiparticle. Mar 11, 2021.

https://phys.org/news/2021-03-birth-quasiparticle.html

<<  These results offer a systematic picture of polaron formation from weak to strong impurity interactions. They reveal three distinct regimes of evolution with dynamical transitions that provide a link between few-body processes and many-body dynamics. Our measurements reveal universal dynamical behaviour in interacting many-body systems and demonstrate new pathways to study non-equilibrium quantum phenomena. >>

Magnus G. Skou, Thomas G. Skov, et al. Non-equilibrium quantum dynamics and formation of the Bose polaron. 

Nat. Phys. (2021). doi: 10.1038/ s41567-021-01184-5. Feb 25, 2021.

https://www.nature.com/articles/s41567-021-01184-5

"three distinct regimes"  

https://www.nature.com/articles/s41567-021-01184-5.epdf?no_publisher_access=1&r3_referer=nature

# gst: multiple external fields can modulate confined active particles

AA << analyze a dilute suspension of active particles confined between walls and subjected to fields that can modulate particle speed as well as orientation. Generally, the particle distribution is different in the bulk compared to near the walls. In the bulk, particles tend to accumulate in the regions of low speed, but in the presence of an orienting field, particles rotate to align with the field and accumulate downstream in the field direction. At the walls, particles tend to accumulate pointing into the walls and thereby exert pressure on walls. But the presence of strong orienting fields can cause the particles to reorient away from the walls >>

<< The pressure at the walls depends on the wall separation and the field strengths. This work demonstrates how multiple fields with different functionalities can be used to control active matter under confinement. >>️

Vaseem A. Shaik, Zhiwei Peng, et al. Confined active matter in external fields. arXiv:2208.09797v1 [cond-mat.soft]. Aug 21, 2022. https://arxiv.org/abs/2208.09797 

Also

keyword 'particle' | 'quasiparticle' in FonT

https://flashontrack.blogspot.com/search?q=particle

https://flashontrack.blogspot.com/search?q=quasiparticle

keyword 'particelle' in Notes

(quasi-stochastic poetry)

https://inkpi.blogspot.com/search?q=particelle

Keywords: gst, particle, particle control

# gst: slow dynamics of a interacting mobile impurity (in a bath of localized particles)

AA << investigate dynamics of a single mobile impurity immersed in a bath of Anderson localized particles and focus on the regime of relatively strong disorder and interactions. In that regime, the dynamics of the system is particularly slow, suggesting, at short times, an occurrence of many-body localization. Considering longer time scales, (AA) show that the latter is a transient effect and that, eventually, the impurity spreads sub-diffusively and induces a gradual delocalization of the Anderson insulator. The phenomenology of the system in the considered regime of slow dynamics includes a sub-diffusive growth of mean square displacement of the impurity, power-law decay of density correlation functions of the Anderson insulator and a power-law growth of entanglement entropy in the system. (AA) observe a similar regime of slow dynamics also when the disorder in the system is replaced by a sufficiently strong quasi-periodic potential. >>

Piotr Sierant, Titas Chanda, Maciej Lewenstein, Jakub Zakrzewski. Slow dynamics of a mobile impurity interacting with an Anderson insulator. arXiv: 2212.07107v1 [cond-mat.dis-nn]. Dec 14, 2022. 

https://arxiv.org/abs/2212.07107

Also

keyword 'particle' | 'quasiparticle' in FonT

https://flashontrack.blogspot.com/search?q=particle

https://flashontrack.blogspot.com/search?q=quasiparticle

keyword 'particelle' in Notes

(quasi-stochastic poetry)

https://inkpi.blogspot.com/search?q=particelle

Keywords: gst, particles, impurity, disorder, sub-diffusive growth, transition, entanglement entropy

# gst: two steady collective states in swarmalators with delayed interactions

AA << investigate the effects of delayed interactions in a population of "swarmalators", generalizations of phase oscillators that both synchronize in time and swarm through space. >>

AA << discover two steady collective states: a state in which swarmalators are essentially motionless in a disk arranged in a pseudo-crystalline order, and a boiling state in which the swarmalators again form a disk, but now the swarmalators near the boundary perform boiling-like convective motions. >>️

Nicholas Blum, Andre Li, et al. Swarmalators with delayed interactions. arXiv: 2210.11417v1 [nlin.AO]. Oct 20, 2022. https://arxiv.org/abs/2210.11417

Also

keyword 'swarm' in FonT

https://flashontrack.blogspot.com/search?q=swarm

keyword 'particle' | 'quasiparticle' in FonT

https://flashontrack.blogspot.com/search?q=particle

https://flashontrack.blogspot.com/search?q=quasiparticle

keyword 'particelle' in Notes

(quasi-stochastic poetry)

https://inkpi.blogspot.com/search?q=particelle

Keywords: gst, particle, swarm

# phys: oscillating quasiparticles, decay and rebirth

<< Admittedly, quasiparticles do decay, however new, identical particle entities emerge from the debris," (..) If this decay proceeds very quickly, an inverse reaction will occur after a certain time and the debris will converge again. This process can recur endlessly and a sustained oscillation between decay and rebirth emerges. >> Ruben Verresen.

Oscillating quasiparticles: the cycle of decay and rebirth. Technical University Munich. June 14, 2019.

https://m.phys.org/news/2019-06-oscillating-quasiparticles-rebirth.html 

Ruben Verresen, Roderich Moessner,  Frank Pollmann. Avoided quasiparticle decay from strong quantum interactions. Nature Physics. doi: 10.1038/s41567-019-0535-3 May 27, 2019.

https://www.nature.com/articles/s41567-019-0535-3