Signature of the existence of a coherently condensed state in a dilute gas above the Bose-Einstein-condensate transition temperature

2015 ◽  
Vol 91 (1) ◽  
Author(s):  
Yinbiao Yang ◽  
Wen-ge Wang
Keyword(s):  
Transition Temperature ◽  
Einstein Condensate ◽  
Condensed State ◽  
Bose Einstein Condensate ◽  
Dilute Gas ◽  
Bose Einstein

scholarly journals Supersolidity of the $\alpha$ cluster structure in the nucleus $^{12}$C

2020 ◽  
Vol 2020 (4) ◽  
Author(s):  
S Ohkubo ◽  
J Takahashi ◽  
Y Yamanaka
Keyword(s):  
Cluster Model ◽  
Cluster Structure ◽  
Einstein Condensate ◽  
Effective Field ◽  
Ground Band ◽  
Model Based ◽  
Bose Einstein Condensate ◽  
Dilute Gas ◽  
Alpha Cluster ◽  
Bose Einstein

Abstract For more than half a century, the structure of $^{12}$C, such as the ground band, has been understood to be well described by the three $\alpha$ cluster model based on a geometrical crystalline picture. On the contrary, recently it has been claimed that the ground state of $^{12}$C is also well described by a nonlocalized cluster model without any of the geometrical configurations originally proposed to explain the dilute gas-like Hoyle state, which is now considered to be a Bose–Einstein condensate of $\alpha$ clusters. The challenging unsolved problem is how we can reconcile the two exclusive $\alpha$ cluster pictures of $^{12}$C, crystalline vs. nonlocalized structure. We show that the crystalline cluster picture and the nonlocalized cluster picture can be reconciled by noticing that they are a manifestation of supersolidity with properties of both crystallinity and superfluidity. This is achieved through a superfluid $\alpha$ cluster model based on effective field theory, which treats the Nambu–Goldstone zero mode rigorously. For several decades, scientists have been searching for a supersolid in nature. Nuclear $\alpha$ cluster structure is considered to be the first confirmed example of a stable supersolid.

The weakly interacting Bose gas at the critical temperature

2019 ◽  
pp. 361-372
Author(s):  
Jean Zinn-Justin
Keyword(s):  
Field Theory ◽  
Phase Transition ◽  
Transition Temperature ◽  
Einstein Condensate ◽  
Einstein Condensation ◽  
Superfluid Phase ◽  
Bose Einstein Condensate ◽  
Repulsive Interactions ◽  
Euclidean Field Theory ◽  
Bose Einstein

Chapter 20 examines effects of weak repulsive interactions in a Bose–Einstein condensate and the transition from Bose–Einstein condensate to superfluid phase transition. Renormalization group methods are used and a universal amplitude is calculated by non–perturbative methods. After the discovery of the predicted Bose–Einstein condensation, which is a property of free bosons, an interesting issue was the effects of weak repulsive interactions. In this chapter, it is shown that, near the transition temperature, the initial non–relativistic field theory can be replaced by a relativistic effective Euclidean field theory known to describe a superfluid phase transition (a dimensional reduction). These theoretical considerations are illustrated by an evaluation of the universal variation of the transition temperature at weak coupling. For this purpose, the O(2) symmetry of the model is generalized to O(N) symmetry, and large N techniques are used.

Macroscopic Squeezing in Bose–Einstein Condensate

1998 ◽  
Vol 12 (18) ◽  
pp. 705-713 ◽  
Author(s):  
Patric Navez
Keyword(s):  
Ground State ◽  
Particle Number ◽  
Einstein Condensate ◽  
Condensed State ◽  
Zero Temperature ◽  
Hartree Fock ◽  
Bose Einstein Condensate ◽  
Normal Behavior ◽  
Particle Number Conservation ◽  
Bose Einstein

We study the ground state of a uniform Bose gas at zero temperature in the Hartree–Fock–Bogoliubov (HFB) approximation. We find a solution of the HFB equations which obeys the Hugenholtz–Pines theorem. This solution imposes a macroscopic squeezing to the condensed state and as a consequence displays large particle number fluctuations. Particle number conservation is restored by building the appropriate U(1) invariant ground state via the superposition of the squeezed states. The condensed particle number distribution of this new ground state is calculated as well as its fluctuations which present a normal behavior.

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