18,555 research outputs found
Stationary Points of Scalar Fields Coupled to Gravity
We investigate the dynamics of gravity coupled to a scalar field using a
non-canonical form of the kinetic term. It is shown that its singular point
represents an attractor for classical solutions and the stationary value of the
field may occur distant from the minimum of the potential. In this paper
properties of universes with such stationary states are considered. We reveal
that such state can be responsible for modern dark energy density.Comment: H. Kroger, invited talk, FFP6, Udine (2004), revised version with
corrected author lis
Gravitational Wave Bursts from Collisions of Primordial Black Holes in Clusters
The rate of gravitational wave bursts from the mergers of massive primordial
black holes in clusters is calculated. Such clusters of black holes can be
formed through phase transitions in the early Universe. The central black holes
in clusters can serve as the seeds of supermassive black holes in galactic
nuclei. The expected burst detection rate by the LISA gravitational wave
detector is estimated.Comment: 10 pages, 2 figure
Precision nonlinear low current meter
Mobile measuring systems that allow small electric parameters to be estimated with high accuracy in real time are relevant for leading edge high-tech applications. In most cases, measurements are carried out with the use of piecewise linear scales and corresponding linear analog-to-digital converters. This technology does not meet the requirements of high measurement accuracy due to errors in the automatic switching of the measuring scale when an input signal varies in a wide range, for example, 100âdB. A new method for measuring small electric parameters based on a nonlinear scale is proposed. The nonlinear analog-to-digital meter having been developed and tested is described. An exponential function with an index m < 1 is used as a scale. The results of measuring nanoampere currents ranging between 1 nA and 1âμA, obtained with the help of the meter model, are presented. © 2019 Author(s)
Separation of lymphocytes by electrophoresis under terrestrial conditions and at zero gravity, phase 3
Electrophoretic mobilities (EPM) of peripheral lymphocytes were studied from normal subjects, chronic hemodialysis patients and kidney transplant recipients. A technique to separate B lymphocytes and null cells from non-T lymphocyte preparation was developed. The experiments were designed to determine which subpopulation of the non-T lymphocytes is primarily affected and shows a decreased EPM in chronic hemodialysis patients and kidney transplant recipients
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Culture and Colonial Legacy: Evidence from Public Goods Games
We conduct a public goods game in three small towns in the Indian state of Rajasthan. Due to historical military conquest, until 1947 these towns were on opposite sides of a colonial border separating British India from the Princely States. Our research design offers a treatment comparison between the towns of (British) Kekri and (Princely) Sarwar, and a control comparison between Princely Sarwar and Shahpura. We find that participants from (British) Kekri are more co-operative in mixed-town groups. The differences are driven by individuals with family ties to the towns, highlighting the enduring effects of colonial rule on co-operation norms
Zeta-Functions for Non-Minimal Operators
We evaluate zeta-functions at for invariant non-minimal
2nd-order vector and tensor operators defined on maximally symmetric even
dimensional spaces. We decompose the operators into their irreducible parts and
obtain their corresponding eigenvalues. Using these eigenvalues, we are able to
explicitly calculate for the cases of Euclidean spaces and
-spheres. In the -sphere case, we make use of the Euler-Maclaurin formula
to develop asymptotic expansions for the required sums. The resulting
values for dimensions 2 to 10 are given in the Appendix.Comment: 26 pages, additional reference
Diversity of universes created by pure gravity
We show that a number of problems of modern cosmology may be solved in the
framework of multidimensional gravity with high-order curvature invariants,
without invoking other fields. We use a method employing a slow-change
approximation, able to work with rather a general form of the gravitational
action, and consider Kaluza-Klein type space-times with one or several extra
factor spaces. A vast choice of effective theories suggested by the present
framework may be stressed: even if the initial Lagrangian is entirely fixed,
one obtains quite different models for different numbers, dimensions and
topologies of the extra factor spaces. As examples of problems addressed we
consider (i) explanation of the present accelerated expansion of the Universe,
with a reasonably small cosmological constant, and the problem of its fine
tuning is considered from a new point of view; (ii) the mechanism of closed
wall production in the early Universe; such walls are necessary for massive
primordial black hole formation which is an important stage in some scenarios
of cosmic structure formation; (iii) sufficient particle production rate at the
end of inflation; (iv) it is shown that our Universe may contain spatial
domains with a macroscopic size of extra dimensions. We also discuss chaotic
attractors appearing at possible nodes of the kinetic term of the effective
scalar field Lagrangian.Comment: 14 pages, 8 figures, revtex4. Final version, some considerations
added in response to referee remark
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