A new rotating generalization of the Damour–Solodukhin wormhole (RDSWH), called Kerr-like wormhole, has recently been proposed and investigated by Bueno et al. for echoes in the gravitational wave ...signal. We show a novel feature of the RDSWH, viz., that the kinematic properties such as the ISCO or marginally stable radius
r
ms
, efficiency
ϵ
and the disk potential
V
eff
are
independent
of
λ
(which means they are identical to their KBH counterparts for any given spin). Differences however appear in the emissivity properties for higher values
0.1
<
λ
≤
1
(say) and for the extreme spin
a
⋆
=
0.998
. The kinematic and emissivity are generic properties as variations of the wormhole mass and the rate of accretion within the model preserve these properties. Specifically, the behavior of the luminosity peak is quite opposite to each other for the two objects, which could be useful from the viewpoint of observations. Apart from this, an estimate of the difference
Δ
λ
in the maxima of flux of radiation
F
(
r
) shows non-zero values but is too tiny to be observable at present for
λ
<
10
-
3
permitted by the strong lensing bound. The broad conclusion is that RDSWH are experimentally indistinguishable from KBH by accretion characteristics.
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It seems surprising that the emissivity properties of the accretion disk (
à la
Page and Thorne) surrounding the Gibbons–Maeda–Garfinkle–Horowitz–Strominger (GMGHS) black holes of heterotic string ...theory have not yet been studied. To fill this gap in the literature, we study the emissivity properties of the thin accretion disks around these black holes both in the Einstein and in the string frame using the Page–Thorne model. For illustration, we choose as a toy model a stellar-sized spherically symmetric black hole and find that, while the emissivity properties do not significantly differ from those of Reissner–Nordström and Schwarzschild black holes, they remarkably differ at GMGHS extreme limits corresponding to naked singularity and wormhole at higher frequencies. These differences provide a novel way to speculatively conclude about different types of objects from the observational point of view.
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We first advance a mathematical novelty that the three geometrically and topologically distinct objects mentioned in the title can be exactly obtained from the Jordan frame vacuum Brans I solution by ...a combination of coordinate transformations, trigonometric identities and complex Wick rotation. Next, we study their respective accretion properties using the Page–Thorne model which studies accretion properties exclusively for
r
≥
r
ms
(the minimally stable radius of particle orbits), while the radii of singularity/throat/horizon
r
<
r
ms
. Also, its Page–Thorne efficiency
ϵ
is found to increase with decreasing
r
ms
and also yields
ϵ
=
0.0572
for Schwarzschild black hole (SBH). But in the singular limit
r
→
r
s
(radius of singularity), we have
ϵ
→
1
giving rise to
100
%
efficiency in agreement with the efficiency of the naked singularity constructed in 10. We show that the differential accretion luminosity
d
L
∞
d
ln
r
of Buchdahl naked singularity (BNS) is always substantially larger than that of SBH, while Eddington luminosity at infinity
L
Edd
∞
for BNS could be arbitrarily large at
r
→
r
s
due to the scalar field
ϕ
that is defined in
(
r
s
,
∞
)
. It is concluded that BNS accretion profiles can still be higher than those of regular objects in the universe.
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It is well known that the Einstein-scalar system of general relativity can in principle yield non-unique exact spinning naked singularities, which lead to unique Kerr black hole when the scalar field ...is switched off. It is a challenging task to observationally distinguish these two types of objects. Since accretion process could be a viable diagnostic for this distinction, the purpose of the present work is to explore whether there could be features in the accretion profiles distinguishing the singularity from a Kerr black hole. Here we study the Novikov–Thorne thin accretion to a
new
spinning naked singularity with a scalar charge
σ
recently reported by Bogush and Gal’tsov (BG). Our study reveals that: (1) the conversion efficiency
ϵ
of the BG naked singularity is
independent
of
σ
and (2) the maxima of emissivity profiles for the BG singularity tend to shift towards the inner disk ISCO boundary
r
=
r
ms
and peak at a value significantly larger than those of a Kerr black hole with the increase of
a
,
σ
and relative shrinking of
-
g
. All these effects are
quantitatively
tabulated, which reveal, for instance, that the flux from the naked singularity could be as high as
10
5
times larger than that of a Kerr black hole. Since these distinguishing features are known to be shared also by other models of naked singularity, it is tempting to speculate that such behavior could be hallmark of naked singularities.
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Wheat is the most important staple crop in Afghanistan and accounts for the main part of cereal production. However, wheat production has been unstable during the last decades and the country depends ...on seed imports. Wheat research in Afghanistan has emphasized releases of new, high-yielding and disease resistant varieties but rates of adoption of improved varieties are uncertain. We applied DNA fingerprinting to assess wheat varieties grown in farmers' fields in four Afghan provinces.
Of 560 samples collected from farmers' fields during the 2015-16 cropping season, 74% were identified as varieties released after 2000, which was more than the number reported by farmers and indicates the general prevalence of use of improved varieties, albeit unknowingly. At the same time, we found that local varieties and landraces have been replaced and were grown by 4% fewer farmers than previously reported. In 309 cases (58.5%), farmers correctly identified the variety they were growing, while in 219 cases (41.5%) farmers did not. We also established a reference library of released varieties, elite breeding lines, and Afghan landraces, which confirms the greater genetic diversity of the landraces and their potential importance as a genetic resource.
Our study is the first in wheat to apply DNA fingerprinting at scale for an accurate assessment of wheat varietal adoption and our findings point up the importance of DNA fingerprinting for accuracy in varietal adoption studies.
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The hoop conjecture, due to Thorne, is a fundamental aspect of black holes in classical general relativity. Recently, generalized classes of regular spherically symmetric static black holes with ...arbitrary exponents coupled to nonlinear electrodynamics have been constructed in the literature. The conjecture in those spacetimes could be violated if only the asymptotic mass
M
∞
is used. To avoid such violations, Hod earlier suggested the appropriate mass function and stated the conjecture in terms of what we call the Hod function. The conjecture can then be applied to any given static spacetime to test whether or not it represents black holes. It is shown here that the conjecture is protected in the above constructed class of generalized spacetimes thus supporting them as black holes. However, it is argued that there are factors, including violation of the conjecture, that militate against the proposed
new
class of solutions to be qualifying as black holes. Finally, we exemplify that the Hod mass
M
(
r
≤
R
)
in the conjecture is exactly the
matter
counterpart of the Misner–Sharp
geometrical
quasilocal mass
m
(
r
≤
R
)
of general relativity. Thus any conclusion based on Hod function is strictly a conclusion of general relativity.
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Recently, a class of static spherically symmetric power law corrected Lorentz violating (LV) Schwarzschild black holes in the Kalb–Ramond model have been derived and studied in the specific range of ...LV parameters (
0
<
λ
≤
2
,
Υ
≥
0
) that correspond to energy condition preserving (
ρ
>
0
) source. On the other hand, there exist well known black holes that do not preserve the energy conditions. In this paper, we shall therefore relax energy conditions and numerically explore the horizon patterns of the enlarged class of LSMA black holes. Four generic types of LV corrected black holes emerge, which interestingly include the analogue of the
braneworld
black hole (
ρ
<
0
) lending to
Υ
a new interpretation of “tidal charge” known as an imprint from the 5
d
bulk in the Randall–Sundrum scenario. We shall then show that Thorne’s hoop conjecture,
H
≤
1
, where
H
is the Hod function, consistently holds for three types and their generalizations. However, intriguingly, it turns out that, for the remaining type (viz., Schwarzschild–de Sitter and its generalizations), the hoop conjecture does
not
hold. It is also shown that braneworld tidal charge black holes increases the LV correction to planetary perihelion advance in contrast to the decrease due to ordinary black holes thereby providing a qualitative distinction between them.
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9.
Saving freshwater from salts Cañedo-Argüelles, M.; Hawkins, C. P.; Kefford, B. J. ...
Science (American Association for the Advancement of Science),
02/2016, Letnik:
351, Številka:
6276
Journal Article
Recenzirano
Ion-specific standards are needed to protect biodiversity
Many human activities—like agriculture and resource extraction—are increasing the total concentration of dissolved inorganic salts (i.e., ...salinity) in freshwaters. Increasing salinity can have adverse effects on human health (
1
); increase the costs of water treatment for human consumption; and damage infrastructure e.g., amounting to $700 million per year in the Border Rivers catchment, Australia (
2
). It can also reduce freshwater biodiversity (
3
); alter ecosystem functions (
4
); and affect economic well-being by altering ecosystem goods and services (e.g., fisheries collapse). Yet water-quality legislation and regulations that target salinity typically focus on drinking water and irrigation water, which does not automatically protect biodiversity. For example, specific electrical conductivities (a proxy for salinity) of 2 mS/cm can be acceptable for drinking and irrigation but could extirpate many freshwater insect species (
3
). We argue that salinity standards for specific ions and ion mixtures, not just for total salinity, should be developed and legally enforced to protect freshwater life and ecosystem services. We identify barriers to setting such standards and recommend management guidelines.
The questions of the one-value solvability of an inverse boundary value problem for a mixed type integro-differential equation with Caputo operators of different fractional orders and spectral ...parameters are considered. The mixed type integro-differential equation with respect to the main unknown function is an inhomogeneous partial integro-differential equation of fractional order in both positive and negative parts of the multidimensional rectangular domain under consideration. This mixed type of equation, with respect to redefinition functions, is a nonlinear Fredholm type integral equation. The fractional Caputo operators’ orders are smaller in the positive part of the domain than the orders of Caputo operators in the negative part of the domain under consideration. Using the method of Fourier series, two systems of countable systems of ordinary fractional integro-differential equations with degenerate kernels and different orders of integro-differentation are obtained. Furthermore, a method of degenerate kernels is used. In order to determine arbitrary integration constants, a linear system of functional algebraic equations is obtained. From the solvability condition of this system are calculated the regular and irregular values of the spectral parameters. The solution of the inverse problem under consideration is obtained in the form of Fourier series. The unique solvability of the problem for regular values of spectral parameters is proved. During the proof of the convergence of the Fourier series, certain properties of the Mittag–Leffler function of two variables, the Cauchy–Schwarz inequality and Bessel inequality, are used. We also studied the continuous dependence of the solution of the problem on small parameters for regular values of spectral parameters. The existence and uniqueness of redefined functions have been justified by solving the systems of two countable systems of nonlinear integral equations. The results are formulated as a theorem.
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