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On the rotation of liquid helium
... Macroscopic excitations play an essential role in many areas of physics, particularly in Bose-Einstein condensates (BECs), which exhibit phenomena such as solitons [1][2][3][4][5][6][7][8][9], quantized vortices [10][11][12][13][14][15][16][17], vortex sheets [18][19][20][21][22][23][24], domain walls [25,26], textures [27][28][29]. These excitations are crucial for understanding the phase, superfluidity and magnetic properties of condensates. ...
... Consequently, a systematic study of macroscopic excitations is essential. In a rotating system, BECs do not align synchronously with the external potential due to their inherent superfluidity [21]. Instead, they often form quantized vortices [30], visually reflecting the superfluid properties of the condensates [24]. ...
Soliton sheets are observed in Bose–Einstein condensates in optical lattice which are formed by superposition of condensates occupying different single-particle states. These structures consist of one-dimensional stationary solitons distributed in the x-direction arranged continuously along the peaks of the optical lattice in the y-direction. Notably, the phase difference across the soliton sheets is periodic and varies linearly with y within each period. So, we refer to this configuration as a ‘soliton sheet’. A velocity difference in the y-component is observed between the two sides of the soliton sheets. Similar velocity distributions can be achieved by aligning an infinite number of isotropic vortices along the peaks of the optical lattice. And the soliton sheets are distinguished by their lack of dependence on phase singularities. This independence enables the formation of soliton sheets even in the absence of phase singularities, highlighting a unique aspect of this structure.
At finite temperature, the stable equilibrium states of coupled two-component Bose Einstein condensations (BECs) with the same conformal mass in both non-rotating and rotating condition can be obtained by studying its real dynamics via holography. The equilibrium state is the state where the free energy reaches the minimum and does not change any more. In the case of no rotation, the spatial phase separated states of the two components become more stable than the miscible condensates state when the direct repulsive inter-component coupling constant η > η c > 0 . Under rotation, the quantum fluid reveals four equilibrium structures of vortex states by varying the η from the miscible region to the phase separated region. Among the four structures, the vortex sheet solution is the most exotic one that appears in the phase separated region.
Aim. The aim of the paper is to study the impact of the works of R. Feynman and J. Schwinger on the development of condensed matter physics in the Soviet Union in the end 1940s and early 1960s. Method. The research is based on the analysis of original works with the use of available literature concerning the issue under consideration. Results. The transfer of the methods of quantum field theory to the many-body problem was a very complex and nontrivial task. The main contribution to its solution was made by physicists from the environment of L.D. Landau. The created apparatus has a great degree of visibility and provides method of calculations brought to automatism. With its help in a large number were solved a variety of problems that are not available with other approaches. The works of Soviet physicists, in turn, had an impact on the work of R. Feynman and J. Schwinger in such areas as the theory of superfluidity, the polaron problem, the Casimir effect. Discussion. The quantum-field theory of many bodies that has been created has decisively contributed to the rapid development of the physics of condensed matter in the next decades, and until now remains the most powerful and effective tool for theoretical research in this field. Here the contribution of Soviet physicists can not be overestimated.
A brief overview of state-of-the-art in developments of new gyros based on: 1) the de Broglie waves of atoms and Bose-Einstein condensates; 2) the properties of superfluid's phase quantization is presented. Sensitivity to the absolute rotation of these types of gyros exceeds the sensitivity of laser gyros (LG) and fiber-optic gyros (FOG) based on Sagnac effect of light waves by nine-eleven orders (109-1011) or by a factor of mc2/hv which is the ratio of atom energy to photon energy. This difference, potentially, allows exceeding significantly the accuracy level that is available for LG and FOG. The devices based on the Sagnac effect of matter-waves were demonstrated and used to detect the Earth's rotation about 30 years ago. Since that time, the accuracy of laboratory samples of such type gyroscopic devices was increased by five orders of magnitude: bias stability is better than 0.0001 deg/h, angle random walk is less than 5×106 deg/h1/2 and the scale factor stability is better than 5 ppm (1a). Technical solutions of the above-mentioned gyro-devices of the world leading research centers are discussed. A brief comparison with LG and FOG technologies is presented.
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