468 research outputs found
Black holes in three-dimensional Einstein-Born-Infeld-dilaton theory
The three-dimensional static and circularly symmetric solution of the
Einstein-Born-Infeld-dilaton system is derived. The solutions corresponding to
low energy string theory are investigated in detail, which include black hole
solutions if the cosmological constant is negative and the mass parameter
exceeds a certain critical value. Some differences between the Born-Infeld
nonlinear electrodynamics and the Maxwell electrodynamics are revealed.Comment: 10 pages LaTeX, 2 eps figures, accepted for publication in PR
GRB980425 in the Off-Axis Jet Model of the Standard GRBs
Using a simple off-axis jet model of GRBs, we can reproduce the observed
unusual properties of the prompt emission of GRB980425, such as the extremely
low isotropic equivalent gamma-ray energy, the low peak energy, the high
fluence ratio, and the long spectral lag when the jet with the standard energy
of ~10^{51} ergs and the opening half-angle of \Delta\theta=~10-30 degree is
seen from the off-axis viewing angle ~\Delta\theta+10/\gamma, where \gamma is a
Lorentz factor of the jet. For our adopted fiducial parameters, if the jet that
caused GRB 980425 is viewed from the on-axis direction, the intrinsic peak
energy Ep(1+z) is ~2.0-4.0 MeV, which corresponds to those of GRB990123 and
GRB021004. Our model might be able to explain the other unusual properties of
this event. We also discuss the connection of GRB980425 in our model with the
X-ray flash, and the origin of a class of GRBs with small E_\gamma such as
GRB030329, GRB980329, GRB981226, and so on.Comment: 4 pages, 2 figures aipTEX, contribution to the 2003 GRB Conference,
held at Santa Fe, N
A possible observational evidence for angular distribution of opening half-angle of GRB jets
We propose a method to estimate the pseudo jet opening half-angle of GRBs
using the spectral peak energy (\Ep)--peak luminosity relation (so called
Yonetoku relation) as well as the \Ep--collimation-corrected -ray
energy relation (so called Ghirlanda relation). For bursts with known jet break
times and redshifts, we compared the pseudo jet opening half-angle with the
standard one and found that the differences are within a factor 2. We apply the
method to 689 long GRBS. We found that the distribution function of the pseudo
jet opening half-angle obeys with
possible cutoffs for although the
log-normal fit is also possible. distribution is compatible with
the structured jet model. From the distribution function we found that the
beaming correction for the rate of GRBs is , which means yr galaxy or only one in type Ib/c supernovae. We
also found the evolution of the distribution function as a function of the
redshift.Comment: 5 pages, 5 figures, submitted to MNRA
Thick Domain Walls Intersecting a Black Hole
We discuss the gravitationally interacting system of a thick domain wall and
a black hole. We numerically solve the scalar field equation in the
Schwarzschild spacetime and show that there exist scalar field configurations
representing thick domain walls intersecting the black hole.Comment: 14 pages, 8 figure
Pressure dependence of Si diffusion in gamma-Fe
The pressure dependence of Si diffusion in γ-Fe was investigated at pressures of 5–15 GPa and temperatures of 1473–1673 K using the Kawai-type multi-anvil apparatus to estimate the rate of mass transportation for the chemical homogenization of the Earth's inner core and those of small terrestrial planets and large satellites. The obtained diffusion coefficients D were fitted to the equation D = D0 exp[−(E* + PV*)/(RT)], where D0 is a constant, E* is the activation energy, P is the pressure, V* is the activation volume, R is the gas constant, and T is the absolute temperature. The least-squares analysis yielded D0 = 10-1.17±0.54 m2/s, E* = 336 ± 16 kJ/mol, and V* = 4.3 ± 0.2 cm3/mol. Moreover, the pressure and temperature dependences of diffusion coefficients of Si in γ-Fe can also be expressed well using homologous temperature scaling, which is expressed as D = D0exp{–g[Tm(P)]/T}, where g is a constant, Tm(P) is the melting temperature at pressure P, and D0 and g are 10-1.0±0.3 m2/s and 22.0 ± 0.7, respectively. The present study indicates that even for 1 billion years, the maximum diffusion length of Si under conditions in planetary and satellite cores is less than ∼1.2 km. Additionally, the estimated strain of plastic deformation in the Earth's inner core, caused by the Harper–Dorn creep, reaches more than 103 at a stress level of 103–104 Pa, although the inner core might be slightly deformed by other mechanisms. The chemical heterogeneity of the inner core can be reduced only via plastic deformation by the Harper–Dorn creep
Selective patterning of netrin-1 as a novel guiding cue for anisotropic dendrogenesis in osteocytes
Although protein patterning approaches have found widespread applications in tuning surface characteristics of biomaterials, selective control of growth in cell body and dendrites utilizing such platforms remains difficult. The functional roles assumed by cell body and dendrites in a physiological milieu have extremely high specificity. In particular, osteocytes embedded inside the mineralized bone matrix are interconnected via dendritic cell processes characterized by an anisotropic arrangement of the lacunar-canalicular system, where the fluid-flow inside the canaliculi system regulates the mechanoresponsive functionalization of bone. Control of cellular networks connected by dendritic cell processes is, therefore, imperative for constructing artificially controlled bone-mimetic structures and as an extension, for gaining insights into the molecular mechanisms underlying dendrogenesis inside the mineralized bone matrix. Here, we report an innovative strategy to induce controlled elongation of cell body or dendritic process structures in selective directions by using the inkjet printing technique. Artificial runways employing netrin-1, inspired by neural architecture, were utilized to trigger controlled elongation in the osteocyte dendritic processes in desired directions. This is the first report, to the best of our knowledge, demonstrating that anisotropic dendrogenesis of osteocytes can be controlled with selective patterning of extracellular proteins, specifically via the axon guidance ligand netrin-1.Matsugaki A., Yamazaki D., Nakano T.. Selective patterning of netrin-1 as a novel guiding cue for anisotropic dendrogenesis in osteocytes. Materials Science and Engineering C, 108, 110391. https://doi.org/10.1016/j.msec.2019.110391
An Off-Axis Jet Model For GRB980425 and Low Energy Gamma-Ray Bursts
Using a simple off-axis jet model of GRBs, we can reproduce the observed
unusual properties of the prompt emission of GRB980425, such as the extremely
low isotropic equivalent gamma-ray energy, the low peak energy, the high
fluence ratio, and the long spectral lag when the jet with the standard energy
of ~10^{51}ergs and the opening half-angle of \Delta\theta=~10-30 degree is
seen from the off-axis viewing angle ~\Delta\theta+10/\gamma, where \gamma is a
Lorentz factor of the jet. For our adopted fiducial parameters, if the jet that
caused GRB980425 is viewed from the on-axis direction, the intrinsic peak
energy Ep(1+z) is ~2.0-4.0 MeV, which corresponds to those of GRB990123 and
GRB021004. We also discuss the connection of GRB980425 in our model with the
X-ray flash, and the origin of a class of GRBs with small E_gamma.Comment: 12 pages, 3 eps figure
A Note on Market Structure with Transaction Costs
Transaction costs play a significant role in financial markets, and many studies have been conducted on this topic to date. Research on this topic may be divided into two categories. The first category of studies examines the optimal trading strategy of the investor who has to pay transaction costs. The second group investigates the optimal transaction costs that ensure the market operates as smoothly as possible, while retaining the profits of the market maker. We consider simultaneous optimization by the investors and the market maker, and analyse the impact of market parameters on the optimized transaction costs
- …