spectral energy density
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Author(s):  
С.Ш. Рехвиашвили ◽  
А.В. Псху ◽  
З.Ч. Маргушев

The spectral energy density of the oscillator radiation is calculated in the dipole approximation. The oscillator motion is described by an equation with fractional integro-differentiation. The fractional oscillator model can describe various types of radiation, including those with a nonexponential relaxation law. Found the shape of the spectral line of radiation. The obtained result is compared with the classical Lorentzian spectrum and experimental emission spectra of monochromatic and phosphor LEDs. The order of fractional integro-differentiation in the model sets the magnitude of the broadening of the radiation spectrum.



2020 ◽  
pp. 73-78
Author(s):  
A. V. Orlov ◽  
V. I. Zelenskiy

This study derives an expression of spectral energy density of acoustic phonons, as well as introducing the basic properties of anharmonic phonons and deriving an expression of their spectral energy density. The description of the vibrations of the atoms of the crystal lattice to this day cannot be considered completely finished, despite the existence of the theory of heat capacity at a constant volume (Debye theory). Debye's theory perfectly explains the law of cubic increase in heat capacity with temperature at low values of the latter. However, at high temperatures, the Debye model seems insufficiently substantiated. In particular, it is not clear for what physical reasons the value of the critical frequency was introduced - the phonon frequency, above which their appearance is impossible. In addition, the spectral energy density of anharmonism phonons is not considered, although this information is extremely important. It is the spectral composition of the anharmonic phonons that is necessary for an objective description of the phonon-phonon interaction in a crystal. In this paper, the principles are stated on the basis of which the spectral energy density of phonons can be calculated. The consideration is carried out for a simple cubic crystal lattice.



2020 ◽  
pp. 73-78
Author(s):  
A. V. Orlov ◽  
V. I. Zelenskiy

This study derives an expression of spectral energy density of acoustic phonons, as well as introducing the basic properties of anharmonic phonons and deriving an expression of their spectral energy density. The description of the vibrations of the atoms of the crystal lattice to this day cannot be considered completely finished, despite the existence of the theory of heat capacity at a constant volume (Debye theory). Debye's theory perfectly explains the law of cubic increase in heat capacity with temperature at low values of the latter. However, at high temperatures, the Debye model seems insufficiently substantiated. In particular, it is not clear for what physical reasons the value of the critical frequency was introduced - the phonon frequency, above which their appearance is impossible. In addition, the spectral energy density of anharmonism phonons is not considered, although this information is extremely important. It is the spectral composition of the anharmonic phonons that is necessary for an objective description of the phonon-phonon interaction in a crystal. In this paper, the principles are stated on the basis of which the spectral energy density of phonons can be calculated. The consideration is carried out for a simple cubic crystal lattice.



2020 ◽  
Vol 16 (1) ◽  
pp. 73-78
Author(s):  
A. V. Orlov ◽  
V. I. Zelenskiy

This study derives an expression of spectral energy density of acoustic phonons, as well as introducing the basic properties of anharmonic phonons and deriving an expression of their spectral energy density. The description of the vibrations of the atoms of the crystal lattice to this day cannot be considered completely finished, despite the existence of the theory of heat capacity at a constant volume (Debye theory). Debye's theory perfectly explains the law of cubic increase in heat capacity with temperature at low values of the latter. However, at high temperatures, the Debye model seems insufficiently substantiated. In particular, it is not clear for what physical reasons the value of the critical frequency was introduced - the phonon frequency, above which their appearance is impossible. In addition, the spectral energy density of anharmonism phonons is not considered, although this information is extremely important. It is the spectral composition of the anharmonic phonons that is necessary for an objective description of the phonon-phonon interaction in a crystal. In this paper, the principles are stated on the basis of which the spectral energy density of phonons can be calculated. The consideration is carried out for a simple cubic crystal lattice.



2020 ◽  
Vol 35 (27) ◽  
pp. 2050165 ◽  
Author(s):  
Massimo Giovannini

In the same way as the energy density associated with the tensor modes of the geometry modifies the evolution of the curvature perturbations, the scalar modes may also indirectly affect the cosmic backgrounds of relic gravitons by inducing higher-order corrections that are only superficially gauge-invariant. This spurious gauge-invariance gets manifest when the effective anisotropic stresses, computed in different coordinate systems, are preliminarily expressed in a form that only depends on the curvature inhomogeneities defined on comoving orthogonal hypersurfaces and on their corresponding time derivatives. Using this observation we demonstrate in general terms that the higher-order contributions derived in diverse coordinate systems coincide when the wavelengths are smaller than the sound horizon defining the evolution of the curvature inhomogeneities but they lead to sharply different results in the opposite limit. A similar drawback arises when the energy density of the relic gravitons is derived from competing energy–momentum pseudotensors and should be consistently taken into account in the related phenomenological discussions.



2020 ◽  
Vol 63 (3) ◽  
pp. 462-466
Author(s):  
A. V. Orlov ◽  
M. A. Gumirov ◽  
V. L. Orlov ◽  
V. I. Zelenskii


2020 ◽  
Vol 33 (1) ◽  
pp. 27-30
Author(s):  
Suniti K. Ghoshal

A thorough investigation of the Planck's black-body radiation reveals several potential flaws. It is found that Planck's final formula suffers from a serious dimensional discrepancy. While it relates to the spectral energy density of the black body radiation, the measured experimental data correspond to the spectral power density. It is shown that Planck's final formula is better written, <mml:math display="inline"> <mml:mi>P</mml:mi> <mml:mo>=</mml:mo> <mml:mi>b</mml:mi> <mml:mi>ν</mml:mi> </mml:math> where <mml:math display="inline"> <mml:mi>P</mml:mi> </mml:math> is power with units <mml:math display="inline"> <mml:mfenced open="[" close="]" separators="|"> <mml:mrow> <mml:mrow> <mml:mrow> <mml:mi>J</mml:mi> </mml:mrow> <mml:mo>/</mml:mo> <mml:mrow> <mml:mi>s</mml:mi> </mml:mrow> </mml:mrow> </mml:mrow> </mml:mfenced> <mml:mo>,</mml:mo> <mml:mo> </mml:mo> <mml:mi>b</mml:mi> </mml:math> is the quantum of energy with units <mml:math display="inline"> <mml:mfenced open="[" close="]" separators="|"> <mml:mrow> <mml:mi>J</mml:mi> </mml:mrow> </mml:mfenced> </mml:math> (numerically equals to Planck's constant, <mml:math display="inline"> <mml:mi>h</mml:mi> </mml:math> ), and <mml:math display="inline"> <mml:mi>ν</mml:mi> </mml:math> is the frequency of the quantum oscillator with units <mml:math display="inline"> <mml:mfenced open="[" close="]" separators="|"> <mml:mrow> <mml:mrow> <mml:mrow> <mml:mn>1</mml:mn> </mml:mrow> <mml:mo>/</mml:mo> <mml:mrow> <mml:mi>s</mml:mi> </mml:mrow> </mml:mrow> </mml:mrow> </mml:mfenced> </mml:math> . It is shown that a simple modification in the Planck's black-body radiation formula brought about by replacing “ <mml:math display="inline"> <mml:mi>h</mml:mi> </mml:math> ” by “ <mml:math display="inline"> <mml:mi>b</mml:mi> </mml:math> ” in it could make it absolutely free from any flaws and discrepancies.



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