367 research outputs found
Black hole solutions to Einstein-Bel-Robinson gravity
By employing a combination of perturbative analytic methods, we study the
physical properties of a static-spherically symmetric black hole in the
framework of the recently proposed Einstien-Bel-Robinson version of gravity. We
show that interestingly the theory propagates a transverse and massive graviton
on a maximally symmetric background with positive energy. There is also a
single ghost-free branch that returns to the Einstein case when \beta\to 0.
Then, we obtain the conserved charges of the theory to study the thermodynamics
of the black hole solutions. We get the thermodynamical quantities and show
that the solutions undergo a first-order phase transition with associated Van
der Waals behavior. We analyze the specific heat, determining that the black
holes are thermodynamically stable over large regions of parametric space.Comment: 16 pages, 5 figure
Charged Black Holes in Einsteinian Quartic Gravity
In this paper, we studied Einsteinian quartic gravity minimally coupled to
electrodynamics in four dimensions. First, by variation action, we obtain the
field equations, and by integration, we obtain a nonlinear third-order
differential equation for the metric function and as well as the
electromagnetic potential. Then, in the context of the Maxwell field, we
discussed the conditions under which the charged black hole exists. Then, we
have demonstrated the thermodynamics and stability of the solution for the case
of positive coupling of quartic theory. Finally, we showed that the charged
black hole solutions of EQG (unlike GR and like ECG) have no inner horizon and
do not conform to the extremal bound of GR. Also, the uniqueness of BH
solutions in this theory does not work anymore.Comment: 13 pages, 6 figure
Effect of nanosilver particles on hatchability of rainbow trout (Oncorhynchus mykiss) egg and survival of the produced larvae
Effect of nanosilver particles was studied on the hatchability of rainbow trout (Oncorhynchus mykiss) egg and survival of the produced larvae at about 12ºC. In the first experiment the water-based nanosilver particles was used at concentrations of 0.5, 1, 2 and 4 mgL^-1 for 30 minutes per day starting 24 hour post egg incubation until the hatching time. The mean percentage of hatchability reached in 27.6±0.2, 38.2±0.1, 41.6±0.4 and 48.6±1.5 in troughs treated with 0.5, 1, 2 and 4 mgL^-1 nanocid, respectively compared with 64.7±0.2 % for trough treated with malachite green at 2 mgL^-1 as positive control (P0.05). These data suggest a possible application of nanosilver particles in aquaculture sector particularly using incubator troughs of trout containing nanosilver materials
Insight into nano-chemical enhanced oil recovery from carbonate reservoirs using environmentally friendly nanomaterials
The use of nanoparticles (NPs) in enhanced oil recovery (EOR) processes is very effective in reducing the interfacial tension (IFT) and surface tension (ST) and altering the wettability of reservoir rocks. The main purpose of this study was to use the newly synthesized nanocomposites (KCl / SiO2 / Xanthan NCs) in EOR applications. Several analytical techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM) were applied to confirm the validity of the synthesized NCs. From the synthesized NCs, nanofluids were prepared at different concentrations of 100-2000 ppm and characterized using electrical conductivity, IFT, and ST measurements. From the obtained results, it can be observed that 1000 ppm is the optimal concentration of the synthesized NCs that had the best performance in EOR applications. The nanofluid with 1000 ppm KCl / SiO2 / Xanthan NCs enabled reducing the IFT and ST from 33 and 70 to 29 and 40 mN/m, respectively. However, the contact angle was highly decreased under the influence of the same nanofluid to 41° and the oil recovery improved by an extra 17.05 % OOIP. To sum up, KCl / SiO2 / Xanthan NCs proved highly effective in altering the wettability of rocks from oil-wet to water-wet and increasing the cumulative oil production
Reconstructing f(R) model from Holographic DE: Using the observational evidence
We investigate the corresponding relation between gravity and an
interacting holographic dark energy. By obtaining conditions needed for some
observational evidence such as, positive acceleration expansion of universe,
crossing the phantom divide line and validity of thermodynamics second law in
an interacting HDE model and corresponding it with mode of gravity we
find a viable model which can explain the present universe. We also
obtain the explicit evolutionary forms of the corresponding scalar field,
potential and scale factor of universe.Comment: 11page. phys. Scr (2012
Switching magnetization with a Weyl semimetal
Energy-efficient magnetization manipulation is a prerequisite for competitive spintronic devices. The Weyl semimetal WTe2 can act as a spin current source that enables magnetization switching of an adjacent ferromagnet at low power consumption and additionally induces chiral magnetism.</p
- …