We investigate the relative phase between two weakly interacting 1D condensates of bosonic atoms after suddenly switching on the tunnel coupling. The following phase dynamics is governed by the quantum sine-Gordon equation. In the semiclassical limit of weak interactions, we observe the parametric amplification of quantum fluctuations leading to the formation of breathers with a finite lifetime. The typical lifetime and density of these "quasibreathers" are derived employing exact solutions of the classical sine-Gordon equation. Both depend on the initial relative phase between the condensates, which is considered as a tunable parameter.
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Entropy (Basel)
November 2024
Departamento de Física, Universidad de Cantabria, 39005 Santander, Spain.
The Einstein equation in a semiclassical approximation is applied to a spherical region of the universe, with the stress-energy tensor consisting of the mass density and pressure of the ΛCDM cosmological model plus an additional contribution due to the quantum vacuum. Expanding the equation in powers of Newton constant G, the vacuum contributes to second order. The result is that at least a part of the acceleration in the expansion of the universe may be due to the quantum vacuum fluctuations.
View Article and Find Full Text PDFEntropy (Basel)
November 2024
Department of Physics, Université Libre de Bruxelles (U.L.B.), Campus de la Plaine C.P. 224, Bvd du Triomphe, 1050 Brussels, Belgium.
In previous work, we investigated thermodynamic processes in systems at the mesoscopic level where traditional thermodynamic descriptions (macroscopic or microscopic) may not be fully adequate. The key result is that entropy in such systems does not change continuously, as in macroscopic systems, but rather in discrete steps characterized by the quantization constant β. This quantization reflects the underlying discrete nature of the collision process in low-dimensional systems and the essential role played by thermodynamic fluctuations at this scale.
View Article and Find Full Text PDFNPJ Quantum Mater
January 2025
NIST Center for Neutron Research, Gaithersburg, MD 20899 USA.
The detailed anisotropic dispersion of the low-temperature, low-energy magnetic excitations of the candidate spin-triplet superconductor UTe is revealed using inelastic neutron scattering. The magnetic excitations emerge from the Brillouin zone boundary at the high symmetry and points and disperse along the crystallographic -axis. In applied magnetic fields to at least = 11 T along the , the magnetism is found to be field-independent in the ( 0) plane.
View Article and Find Full Text PDFChem Biodivers
January 2025
Center of Plasma Nano-interface Engineering, Kyushu University, Fukuoka, Japan.
In recent years, there has been an increase in the study of the mechanisms behind plasma oncology. For this, many wet lab experiments and computational studies were conducted. Computational studies give an advantage in examining protein structures that are costly to extract in enough amounts to analyze the biophysical properties following plasma treatment.
View Article and Find Full Text PDFPhys Rev Lett
December 2024
Freie Universität Berlin, Department of Mathematics and Computer Science, Arnimallee 6, 14195 Berlin, Germany.
Quantum batteries are energy-storing devices, governed by quantum mechanics, that promise high charging performance thanks to collective effects. Because of its experimental feasibility, the Dicke battery-which comprises N two-level systems coupled to a common photon mode-is one of the most promising designs for quantum batteries. However, the chaotic nature of the model severely hinders the extractable energy (ergotropy).
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