505 research outputs found
A theory of evolving natural constants embracing Einstein's theory of general relativity and Dirac's large number hypothesis
Taking a hint from Dirac's large number hypothesis, we note the existence of
cosmic combined conservation laws that work to cosmologically long time. We
thus modify or generalize Einstein's theory of general relativity with fixed
gravitation constant to a theory for varying , which can be applied to
cosmology without inconsistency, where a tensor arising from the variation of G
takes the place of the cosmological constant term. We then develop on this
basis a systematic theory of evolving natural constants by finding out their cosmic combined counterparts involving factors of
appropriate powers of that remain truly constant to cosmologically long
time. As varies so little in recent centuries, so we take these natural
constants to be constant.Comment: 29 pages, revtex
Polymer Nanocomposites for Wind Energy Applications: Perspectives and Computational Modeling
Strength and reliability of wind blades produced from polymer composites are the important preconditions
for the successful development of wind energy. One of the ways to increase the reliability and lifetime
of polymer matrix composites is the nanoengineering of matrix or fiber / matrix interfaces in these composites.
The potential and results of nanoclay reinforcements for the improvement of the mechanical properties
of polymer composites are investigated using continuum mechanics and micromechanics methods and
effective phase model. It is demonstrated that nanoreinforcement allows increasing the stiffness and
strength of composites.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3550
Slowly rotating black holes in the Horava-Lifshitz gravity
We investigate slowly rotating black holes in the Ho\v{r}ava-Lifshitz (HL)
gravity. For and , we find a slowly rotating black
hole of the Kehagias-Sfetsos solution in asymptotically flat spacetimes. We
discuss their thermodynamic properties by computing mass, temperature, angular
momentum, and angular velocity on the horizon.Comment: 12 pages, no figures, version to appear in EPJ
Charge and spin configurations in the coupled quantum dots with Coulomb correlations induced by tunneling current
We investigated the peculiarities of non-equilibrium charge states and spin
configurations in the system of two strongly coupled quantum dots (QDs) weakly
connected to the electrodes in the presence of Coulomb correlations. We
analyzed the modification of non-equilibrium charge states and different spin
configurations of the system in a wide range of applied bias voltage and
revealed well pronounced ranges of system parameters where negative tunneling
conductivity appears due to the Coulomb correlations.Comment: 10 pages, 6 figure
Distributed phase-covariant cloning with atomic ensembles via quantum Zeno dynamics
We propose an interesting scheme for distributed orbital state quantum
cloning with atomic ensembles based on the quantum Zeno dynamics. These atomic
ensembles which consist of identical three-level atoms are trapped in distant
cavities connected by a single-mode integrated optical star coupler. These
qubits can be manipulated through appropriate modulation of the coupling
constants between atomic ensemble and classical field, and the cavity decay can
be largely suppressed as the number of atoms in the ensemble qubits increases.
The fidelity of each cloned qubit can be obtained with analytic result. The
present scheme provides a new way to construct the quantum communication
network.Comment: 5 pages, 4 figure
Dimensionless cosmology
Although it is well known that any consideration of the variations of
fundamental constants should be restricted to their dimensionless combinations,
the literature on variations of the gravitational constant is entirely
dimensionful. To illustrate applications of this to cosmology, we explicitly
give a dimensionless version of the parameters of the standard cosmological
model, and describe the physics of Big Bang Neucleosynthesis and recombination
in a dimensionless manner. The issue that appears to have been missed in many
studies is that in cosmology the strength of gravity is bound up in the
cosmological equations, and the epoch at which we live is a crucial part of the
model. We argue that it is useful to consider the hypothetical situation of
communicating with another civilization (with entirely different units),
comparing only dimensionless constants, in order to decide if we live in a
Universe governed by precisely the same physical laws. In this thought
experiment, we would also have to compare epochs, which can be defined by
giving the value of any {\it one} of the evolving cosmological parameters. By
setting things up carefully in this way one can avoid inconsistent results when
considering variable constants, caused by effectively fixing more than one
parameter today. We show examples of this effect by considering microwave
background anisotropies, being careful to maintain dimensionlessness
throughout. We present Fisher matrix calculations to estimate how well the fine
structure constants for electromagnetism and gravity can be determined with
future microwave background experiments. We highlight how one can be misled by
simply adding to the usual cosmological parameter set
Polluted lake restoration to promote sustainability in the Yangtze River Basin, China
China has sought to address water pollution in the last decade by introducing a wide range of laws and regulations (Table S1), which led to nationwide water quality improvement. However, recent quantitative assessment of progress toward Sustainable Development Goals (SDGs) in China suggests that some SDGs underpinning goals for water pollution and biodiversity have not been met. Specifically, tests on water quality improvement in lakes have had contradictory results, leading to confusion about water quality improvement in China
Radiative transitions among the vector and scalar heavy quarkonium states with covariant light-front quark model
In this article, we study the radiative transitions among the vector and
scalar heavy quarkonium states with the covariant light-front quark model. In
calculations, we observe that the radiative decay widths are sensitive to the
constituent quark masses and the shape parameters of the wave-functions, and
reproduce the experimental data with suitable parameters.Comment: 11 pages, 7 figure
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