Anand K. Bhatia

Anand K. Bhatia

Institution: Heliophysics Science Division, NASA/Goddard Space Flight Center,

Email: d.k.bhatia@nasa.gov

The excitation cross-sections of the nS states of atomic hydrogen, n = 2 to 6, by electron
impact on the ground state of atomic hydrogen were calculated using the variational polarizedorbital method at various incident electron energies in the range 10 to 122 eV. Converged excitation
cross-sectio...

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The excitation cross-sections of the nS states of atomic hydrogen, n = 2 to 6, by electron
impact on the ground state of atomic hydrogen were calculated using the variational polarizedorbital method at various incident electron energies in the range 10 to 122 eV. Converged excitation
cross-sections were obtained using sixteen partial waves (L = 0 to 15). Excitation cross-sections to
2S state, calculated earlier, were calculated at higher energies than before. Results obtained using
the hybrid theory (variational polarized orbital method) are compared to those obtained using other
approaches such as the Born–Oppenheimer, close-coupling, R-matrix, and complex-exterior scaling
methods using only the spherical symmetric wave functions. Phase shifts and elastic cross-sections
are given at various energies and angular momenta. Excitation rate coefficients were calculated at
various electron temperatures, which are required for plasma diagnostics in solar and astrophysics to
infer plasma parameters. Excitation cross-sections are compared with those obtained by positron
impact excitation.

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11 months ago
In the article, the fireball formed in the collision of relativistic nuclei is considered as a quantum object. Based on this, an attempt is made to explain the difference in the measurements of hyperon yields in the two experiments - NA49 and NA57. Using the basic principles of quantum mechanics, it...

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In the article, the fireball formed in the collision of relativistic nuclei is considered as a quantum object. Based on this, an attempt is made to explain the difference in the measurements of hyperon yields in the two experiments - NA49 and NA57. Using the basic principles of quantum mechanics, it was shown that a fireball can have two quantum states - with and without ignited Quark-Gluon Plasma (QGP). With an increase of the collision energy of heavy ions, the probability of QGP ignition increases. At the same time, the probability of the formation of a fireball without igniting the QGP also remains not zero

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11 months ago
Mohammad R. Garousi

Mohammad R. Garousi

Institution: Department of Physics, Faculty of Science, Ferdowsi University of Mashhad,

Email: garousi@um.ac.ir

Recently, using the assumption that the string theory effective action at the critical dimension is background independent, the classical on-shell effective action of the bosonic string theory at order α in a spacetime manifold without boundary has been reproduced, up to an overall parameter, by im...

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Recently, using the assumption that the string theory effective action at the critical dimension is background independent, the classical on-shell effective action of the bosonic string theory at order α in a spacetime manifold without boundary has been reproduced, up to an overall parameter, by imposing the O(1, 1) symmetry when the background has a circle. In the presence of the boundary, we consider a background which has boundary and a circle such that the unit normal vector of the boundary is independent of the circle. Then the O(1, 1) symmetry can fix the bulk action without using the lowest order equation of motion. Moreover, the above constraints and the constraint from the principle of the least action in the presence of boundary can fix the boundary action, up to five boundary parameters. In the least action principle, we assume that not only the values
of the massless fields but also the values of their first derivatives are arbitrary on the boundary. We have also observed
that the cosmological reduction of the leading order action in the presence of the Hawking–Gibbons boundary term, produces zero cosmological boundary action. Imposing this as another constraint on the boundary couplings at order α, we find the boundary action up to two parameters. For a specific value for these two parameters, the gravity couplings in the boundary become the Chern–Simons gravity plus another term which has the Laplacian of the extrinsic curvature.

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11 months ago
The relative velocity between objects with finite velocity affects the reaction
between them. This effect is known as general Doppler effect. The Laser Interferometer
Gravitational-Wave Observatory (LIGO) discovered gravitational waves and found their
speed to be equal to the speed of light c. Gr...

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The relative velocity between objects with finite velocity affects the reaction
between them. This effect is known as general Doppler effect. The Laser Interferometer
Gravitational-Wave Observatory (LIGO) discovered gravitational waves and found their
speed to be equal to the speed of light c. Gravitational waves are generated following
a disturbance in the gravitational field; they affect the gravitational force on an object.
Just as light waves are subject to the Doppler effect, so are gravitational waves. This
article explores the following research questions concerning gravitational waves: Is there
a linear relationship between gravity and velocity? Can the speed of a gravitational wave
represent the speed of the gravitational field (the speed of the action of the gravitational
field upon the object)? What is the speed of the gravitational field? What is the spatial
distribution of gravitational waves? Do gravitational waves caused by the revolution of
the Sun affect planetary precession? Can we modify Newton’s gravitational equation
through the influence of gravitational waves?

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11 months ago