21,018 research outputs found
Evaluation of specific heat for superfluid helium between 0 - 2.1 K based on nonlinear theory
The specific heat of liquid helium was calculated theoretically in the Landau
theory. The results deviate from experimental data in the temperature region of
1.3 - 2.1 K. Many theorists subsequently improved the results of the Landau
theory by applying temperature dependence of the elementary excitation energy.
As well known, many-body system has a total energy of Galilean covariant form.
Therefore, the total energy of liquid helium has a nonlinear form for the
number distribution function. The function form can be determined using the
excitation energy at zero temperature and the latent heat per helium atom at
zero temperature. The nonlinear form produces new temperature dependence for
the excitation energy from Bose condensate. We evaluate the specific heat using
iteration method. The calculation results of the second iteration show good
agreement with the experimental data in the temperature region of 0 - 2.1 K,
where we have only used the elementary excitation energy at 1.1 K.Comment: 6 pages, 3 figures, submitted to Journal of Physics: Conference
Serie
A General Analytic Formula for the Spectral Index of the Density Perturbations produced during Inflation
The standard calculation of the spectrum of density perturbations produced
during inflation assumes that there is only one real dynamical degree of
freedom during inflation. However, there is no reason to believe that this is
actually the case. In this paper we derive general analytic formulae for the
spectrum and spectral index of the density perturbations produced during
inflation.Comment: 10 pages, more explanation and references added, version to be
published in Progress of Theoretical Physic
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