NEUTRINO ENERGY LOSS AT MATTER-RADIATION DECOUPLING PHASE

2009 ◽  
Vol 24 (11n13) ◽  
pp. 1051-1054
Author(s):  
UNGKU FERWANI SALWA UNGKU IBRAHIM ◽  
NOR SOFIAH AHMAD ◽  
NORHASLIZA YUSOF ◽  
HASAN ABU KASSIM
Keyword(s):  
Energy Loss ◽  
Neutrino Energy ◽  
Electron Neutrino ◽  
Stopping Power ◽  
Power Equation ◽  
Electron Positron ◽  
Extra Energy ◽  
Expansion Of The Universe ◽  
Current Interaction ◽  
The Universe

Neutrinos are produced copiously in the early universe. Neutrinos and antineutrinos ceased to be in equilibrium with radiation when the weak interaction rate becomes slower than the rate expansion of the universe. The ratio of the temperature of the photon to the temperature of the neutrino at this stage is Tγ/Tν = (11/4)1/3. We investigate the neutrino energy loss due to the oscillation of the electron neutrino into a different flavor in the charged-current interaction of νe-e- based on the work of Sulaksono and Simanjuntak. The energy loss from the neutrinos ΔEν during the decoupling of the neutrinos with the rest of the matter would be a gain in the energy of the electrons and can be obtained from the integration of stopping power equation ΔEν = (dEν/dT-1)dT-1 where Eν and T are the energy of the neutrinos and the temperature respectively. When the universe expands and matter-radiation decouples, an extra energy will be transferred to the photons via the annihilation of the electron-positron pairs, e++e-→γ+γ. This consequently will increase the temperature of the photons. The net effect to the lowest order is an increase in the ratio of the photon temperature to the neutrino temperature. The magnitude of energy loss of the neutrino is ∼10-4-10-5 MeV for the probability of conversion of νe → νi (i = μ,τ) between 0 to 1.0.

scholarly journals Energy loss and effective charge of low-energy oxygen ions in partially ionized plasma

2000 ◽  
Vol 18 (4) ◽  
pp. 639-646
Author(s):  
K. NISHIGORI ◽  
U. NEUNER ◽  
M. TAKIZAWA ◽  
M. KOJIMA ◽  
T. SAGAMI ◽  
...  
Keyword(s):  
Energy Loss ◽  
Charge Distribution ◽  
Effective Charge ◽  
Low Energy ◽  
Stopping Power ◽  
Oxygen Ions ◽  
Power Equation ◽  
Slow Ions ◽  
Partially Ionized ◽  
Peak Value

This article reports on the interaction between slow ions and a partially ionized plasma. Temporal evolutions of energy loss and charge distribution of 2.4 MeV oxygen beams in the laser-induced polyethylene plasma were measured. The charge distribution showed strong stripping ability in the early phase of the plasma. Stopping power deduced from the experimental energy loss was 1.9 times larger than that for the solid. The effective charge of the projectile ion was estimated from the yields of 4+ and 6+ states. The peak value of the effective charge was 1.4 times larger than that of the solid. The stopping power equation given by Sigmund was extended for the partially ionized plasma and it could reproduce the measured energy loss.

QUANTUM-ELECTRODYNAMIC PROCESSES IN A RADIATION-DOMINATED ROBERTSON-WALKER UNIVERSE

1992 ◽  
Vol 07 (09) ◽  
pp. 2055-2086 ◽  
Author(s):  
I.L. BUCHBINDER ◽  
L.I. TSAREGORODTSEV
Keyword(s):  
Quantum Electrodynamics ◽  
Line Element ◽  
Total Probability ◽  
Matrix Formalism ◽  
Differential Probability ◽  
Electron Positron ◽  
S Matrix ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Electron Positron Pair

Quantum electrodynamics in an expanding Robertson-Walker universe with the line element ds2=dt2 – a2(t)(dx2+dy2+dz2) (radiation-dominated universe) is considered. The differential probability of bremsstrahlung of an electron in the external gravitational field and the differential probability of an electron-positron pair and photon creation from the vacuum are calculated by using the perturbative S-matrix formalism. The behavior of these probabilities in different kinematic regions is investigated. The total probabilities are shown to be finite. In conclusion, the total probability of a pair and photon creation from vacuum We is compared with the total probability of pair production due to an expansion of the universe W0. The comparison shows that We=1.9·10−2W0 at about the Compton time of an electron.

Time varying parameter in modified Chaplygin gas cosmology

2020 ◽  
Vol 35 (16) ◽  
pp. 2050128
Author(s):  
Koijam Manihar Singh ◽  
K. L. Mahanta ◽  
Longjam Parbati Devi ◽  
R. R. Sahoo
Keyword(s):  
Dark Energy ◽  
Energy Density ◽  
Physical World ◽  
Chaplygin Gas ◽  
Accelerated Expansion ◽  
Interesting Phenomenon ◽  
Extra Energy ◽  
Time Varying Parameter ◽  
Expansion Of The Universe ◽  
The Universe

In the course of study of the evolution of the universe, it is seen that perhaps the extra energy generated and particles created due to the accelerated expansion of the universe might be absorbed by the dark energy and dark matter which are already existing in this universe. It is found that the energy density of dark energy can be expressed as a function of the energy density of the remaining matter portion of the universe which shows that the different components of the universe are correlated. According to the forms of the different types of interaction occurring between dark energy and the other different contents of the universe it may be possible to utilize the dark energy in different ways as it may take different forms of energy. As an interesting phenomenon, it is also observed that the concept of negative time may exist in this universe, and it may revolutionize some of the original concepts of nature and the physical world.

scholarly journals Variation of the fine-structure constant caused by expansion of the Universe

2019 ◽  
Vol 34 (38) ◽  
pp. 1950315
Author(s):  
Ivan A. Cardenas ◽  
Anton A. Lipovka
Keyword(s):  
Fine Structure ◽  
Riemannian Manifold ◽  
Energy Loss ◽  
Structure Constant ◽  
Fine Structure Constant ◽  
Experimental Limit ◽  
Planck Constant ◽  
Expansion Of The Universe ◽  
Em Field ◽  
The Universe

In this paper, we evaluate the fine-structure constant variation that should take place as the pseudo-Riemannian Universe expands and its curvature is changed adiabatically. Such variation of the fine-structure constant is attributed to an energy loss by an extended physical system (consisting of baryonic component and electromagnetic (EM) field) due to expansion of our Universe. Obtained ratio [Formula: see text] (per second) is only five times smaller than actually reported experimental limit on this value. For this reason, the obtained variation can probably be measured within a couple of years. To argue the correctness of our approach, we calculate the Planck constant as adiabatic invariant of the EM field propagated on the pseudo-Riemannian manifold characterized by slowly varied geometry. Finally, we discuss the double clock experiment based on Al[Formula: see text] and Hg[Formula: see text] clocks carried out by Rosenband et al. (Science 2008). We show that in this case (when the fine-structure constant is changed adiabatically), the method based on double clock experiment cannot be applied to measure the fine-structure constant variation.

Stopping-power determination for compound by EELS

1994 ◽  
Vol 52 ◽  
pp. 948-949 ◽  
Author(s):  
David C. Joy ◽  
Suichu Luo ◽  
John R. Dunlap ◽  
Dick Williams ◽  
Siqi Cao
Keyword(s):  
Energy Loss ◽  
Electron Energy ◽  
Electron Energy Loss Spectroscopy ◽  
Materials Science ◽  
Average Energy ◽  
Stopping Power ◽  
Accurate Information ◽  
Power Calculation ◽  
Coulomb Collisions ◽  
Electron Energy Loss

In Physics, Chemistry, Materials Science, Biology and Medicine, it is very important to have accurate information about the stopping power of various media for electrons, that is the average energy loss per unit pathlength due to inelastic Coulomb collisions with atomic electrons of the specimen along their trajectories. Techniques such as photoemission spectroscopy, Auger electron spectroscopy, and electron energy loss spectroscopy have been used in the measurements of electron-solid interaction. In this paper we present a comprehensive technique which combines experimental and theoretical work to determine the electron stopping power for various materials by electron energy loss spectroscopy (EELS ). As an example, we measured stopping power for Si, C, and their compound SiC. The method, results and discussion are described briefly as below.The stopping power calculation is based on the modified Bethe formula at low energy:where Neff and Ieff are the effective values of the mean ionization potential, and the number of electrons participating in the process respectively. Neff and Ieff can be obtained from the sum rule relations as we discussed before3 using the energy loss function Im(−1/ε).

Black Hole Universe: a grand cosmic recycler and Big Bang generator?

2019 ◽  
Author(s):  
Matheus Pereira Lobo
Keyword(s):  
Black Hole ◽  
Big Bang ◽  
Subsequent Increase ◽  
Expansion Of The Universe ◽  
The Universe

We propose the discussion of a highly speculative idea for the scenario where black hole collisions and their subsequent increase in sizes exceed the expansion of the universe.

Cosmological constant

2018 ◽  
Author(s):  
Michael Kachelriess
Keyword(s):  
Dark Energy ◽  
Cosmological Constant ◽  
Accelerated Expansion ◽  
Vacuum Fluctuations ◽  
Present Epoch ◽  
Modify Gravity ◽  
Expansion Of The Universe ◽  
The Universe

The contribution of vacuum fluctuations to the cosmological constant is reconsidered studying the dependence on the used regularisation scheme. Then alternative explanations for the observed accelerated expansion of the universe in the present epoch are introduced which either modify gravity or add a new component of matter, dubbed dark energy. The chapter closes with some comments on attempts to quantise gravity.

scholarly journals Mixed fluid cosmological model in f(R, T) gravity

2020 ◽  
Vol 98 (11) ◽  
pp. 1015-1022 ◽  
Author(s):  
Parbati Sahoo ◽  
Barkha Taori ◽  
K.L. Mahanta
Keyword(s):  
Cosmological Model ◽  
Bianchi Type ◽  
Type I ◽  
Time Varying ◽  
Eos Parameter ◽  
Barotropic Fluid ◽  
Rotationally Symmetric ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Mixed Fluid

We construct a locally rotationally symmetric (LRS) Bianchi type-I cosmological model in f(R, T) theory of gravity when the source of gravitation is a mixture of barotropic fluid and dark energy (DE) by employing a time-varying deceleration parameter. We observe through the behavior of the state finder parameters (r, s) that our model begins from the Einstein static era and goes to ΛCDM era. The equation of state (EOS) parameter (ωd) for DE varies from the phantom (ω < –1) phase to quintessence (ω > –1) phase, which is consistent with observational results. It is found that the discussed model can reproduce the current accelerating phase of the expansion of the universe.

scholarly journals Taxonomy of Dark Energy Models

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 163
Author(s):  
Verónica Motta ◽  
Miguel A. García-Aspeitia ◽  
Alberto Hernández-Almada ◽  
Juan Magaña ◽  
Tomás Verdugo
Keyword(s):  
Dark Energy ◽  
Cold Dark Matter ◽  
Accelerated Expansion ◽  
Energy Component ◽  
The Past ◽  
Energy Models ◽  
The Status ◽  
Expansion Of The Universe ◽  
The Universe ◽  
Unknown Component

The accelerated expansion of the Universe is one of the main discoveries of the past decades, indicating the presence of an unknown component: the dark energy. Evidence of its presence is being gathered by a succession of observational experiments with increasing precision in its measurements. However, the most accepted model for explaining the dynamic of our Universe, the so-called Lambda cold dark matter, faces several problems related to the nature of such energy component. This has led to a growing exploration of alternative models attempting to solve those drawbacks. In this review, we briefly summarize the characteristics of a (non-exhaustive) list of dark energy models as well as some of the most used cosmological samples. Next, we discuss how to constrain each model’s parameters using observational data. Finally, we summarize the status of dark energy modeling.

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