An exact spherically symmetric space–time in Einstein–Cartan theory

By adopting the Newman–Penrose–Jogia–Griffith formalism, the field equations in Einstein–Cartan theory for matter with spin creating torsion in space–time are solved in a spherically symmetric space–time by assuming only one non-vanishing component of spin. The exact solution might be the prototype for more realistic models.     

Basic thermodynamic parameters of a black hole resulting from a Yukawa type of correction to the metric

There has been a renewed interest in the recent years in the possibility of deviations from the predictions of Newton’s “inverse-square law” of universal gravitation. One of the reasons for renewing this interest lies in various theoretical attempts to construct a unified elementary particle theory, in which there is a natural prediction of new forces over macroscopic distances. Therefore the existence of such a force would only coexist with gravity, and in principle could only be detected as a deviation from the inverse square law, or in the “universality of free fall” experiments. New experimental techniques such that of Sagnac interferometry can help explore the range of the Yukawa correction λ≥10¹⁴ m where such forces might be present. It may be, that future space missions might be operating in this range which has been unexplored for very long time. In this paper we derive the basic thermodynamic parameters of such a Yukawa stationary spherically symmetric black hole. First, the expression for the event horizon of such a black hole is derived, with the help of which the temperature, entropy and heat capacity of this particular black hole are obtained. We have also obtained analytical expressions for the change of mass of such black hole, and also its corresponding evaporation time.     

Calculation of radar signal delays in the vicinity of the Sun due to the contribution of a Yukawa correction term in the gravitational potential

There has been a renewed interest in the recent years in the possibility of deviations from the predictions of Newton’s “inverse-square law” of universal gravitation. One of the reasons for renewing this interest lies in various theoretical attempts to construct a unified elementary particle theory, in which there is a natural prediction of new forces over macroscopic distances. Therefore the existence of such a force would only coexist with gravity, and in principle could only be detected as a deviation from the inverse square law, or in the “universality of free fall” experiments. New experimental techniques such that of Sagnac interferometry can help explore the range of the Yukawa correction λ≥10¹⁴ m where such forces might be present. It may be, that future space missions might be operating in this range which has been unexplored for very long time. To study the effect of the Yukawa correction to the gravitational potential and its corresponding signal delay in the vicinity of the Sun, we use a spherically symmetric modified space time metric where the Yukawa correction its added to the gravitational potential. Next, the Yukawa correction contribution to the signal delay is evaluated. In the case where the distance of closest approach is much less than the range λ, it results to a signal time delay that satisfies the relation t(b<λ)≅37.7t(b=λ).     

Inhomogeneous Cylindrically-Symmetric Models with Varying Cosmological Term

We consider Einstein's equations with variable cosmological constant in the presence of a perfect fluid for the inhomogeneous cylindrically-symmetric space–time. We find two solutions under this conditions and analyze our solutions with respect to the constants.     

Magnetic Field Structures in a Facular Region Observed by THEMIS and <Emphasis Type="Italic">Hinode</Emphasis>

We study the space – time distributions of intensity fluctuations in 2 – 3 hour sequences of multi-spectral, high-resolution, high-cadence, broad-band filtergram images of the Sun made by the SOT – FG system aboard the Hinode spacecraft. In the frequency range 5.5<f<8.0 mHz both G-band and Ca ii H-line oscillations are suppressed in the presence of magnetic fields, but the suppression disappears for f>10 mHz. By looking at G-band frequencies above 10 mHz we find that the oscillatory power, both at these frequencies and at lower frequencies, lies in a mesh pattern with cell scale 2 – 3 Mm, clearly larger than normal granulation, and with correlation times on the order of hours. The mesh pattern lies in the dark lanes between stable cells found in time-integrated G-band intensity images. It also underlies part of the bright pattern in time-integrated H-line emission. This discovery may reflect dynamical constraints on the sizes of rising granular convection cells together with the turbulence created in strong intercellular downflows.     

Search For Correlations Between Batse Gamma-Ray Bursts and Supernovae

We report on our statistical research of space–time correlated supernovae and CGRO-BATSE gamma-ray bursts (GRBs). There exists a significantly higher abundance of core-collapse supernovae among the correlated supernovae, but the subset of all correlated objects does not seem to be physically different from the whole set.     

Energy–Momentum In The Viscous Kasner-Type Universe In Teleparallel Gravity

Using the teleparallel gravity versions of the Einstein and Landau–Lifshitz’s energy and/or momentum complexes, I obtain the energy and momentum of the universe in viscous Kasner-type cosmological models. The energy and momentum components (due to matter plus field) are found to be zero and this agree with a previous work of Rosen and Johri et al., who investigated the problem of the energy in Friedmann–Robertson–Walker (FRW) universe. The result that the total energy and momentum components of the universe in these models is zero same as Bergmann–Thomson’s energy–momentum and props the viewpoint of Tryon. Rosen found that the energy of the FRW space–time is zero, which agrees with the studies of Tryon. PACs Numbers: 04.20.-q; 04.50.+h An erratum to this article is available at .     

Macroscopic quantum resonators (MAQRO)

Quantum physics challenges our understanding of the nature of physical reality and of space-time and suggests the necessity of radical revisions of their underlying concepts. Experimental tests of quantum phenomena involving massive macroscopic objects would provide novel insights into these fundamental questions. Making use of the unique environment provided by space, MAQRO aims at investigating this largely unexplored realm of macroscopic quantum physics. MAQRO has originally been proposed as a medium-sized fundamental-science space mission for the 2010 call of Cosmic Vision. MAQRO unites two experiments: DECIDE (DECoherence In Double-Slit Experiments) and CASE (Comparative Acceleration Sensing Experiment). The main scientific objective of MAQRO, which is addressed by the experiment DECIDE, is to test the predictions of quantum theory for quantum superpositions of macroscopic objects containing more than 10⁸ atoms. Under these conditions, deviations due to various suggested alternative models to quantum theory would become visible. These models have been suggested to harmonize the paradoxical quantum phenomena both with the classical macroscopic world and with our notion of Minkowski space-time. The second scientific objective of MAQRO, which is addressed by the experiment CASE, is to demonstrate the performance of a novel type of inertial sensor based on optically trapped microspheres. CASE is a technology demonstrator that shows how the modular design of DECIDE allows to easily incorporate it with other missions that have compatible requirements in terms of spacecraft and orbit. CASE can, at the same time, serve as a test bench for the weak equivalence principle, i.e., the universality of free fall with test-masses differing in their mass by 7 orders of magnitude.     

Matter wave explorer of gravity (MWXG)

In response to ESA’s Call for proposals of 5 March 2007 of the COSMIC VISION 2015–2025 plan of the ESA science programme, we propose a M-class satellite mission to test of the Equivalence Principle in the quantum domain by investigating the extended free fall of matter waves instead of macroscopic bodies as in the case of GAUGE, MICROSCOPE or STEP. The satellite, called Matter Wave Explorer of Gravity, will carry an experiment to test gravity, namely the measurement of the equal rate of free fall with various isotopes of distinct atomic species with precision cold atom interferometry in the vicinity of the earth. This will allow for a first quantum test the Equivalence Principle with spin polarised particles and with pure fermionic and bosonic atomic ensembles. Due to the space conditions, the free fall of Rubidium and Potassium isotopes will be compared with a maximum accelerational sensitivity of 5·10^− 16 m/s² corresponding to an accuracy of the test of the Equivalence Principle of 1 part in 10¹⁶. Besides the primary scientific goal, the quantum test of the Equivalence Principle, the mission can be extended to provide additional information about the gravitational field of the earth or for testing theories of fundamental processes of decoherence which are investigated by various theory groups in the context of quantum gravity phenomenology. In this proposal we present in detail the mission objectives and the technical aspects of the proposed mission.     

Non-Existence Of <Emphasis Type="Italic">N</Emphasis>-Dimensional Static Plane Symmetric Solutions In Bimetric Relativity Theory

A problem of static plane symmetric metric in the perfect fluid, the mesonic massive scalar field and in their coupling is studied in Rosen’s (1973) bimetric theory of relativity. It was found that the matter field like either perfect fluid or mesonic massive scalar field or their coupling does not survive in bimetric theory of gravitation when the space–time is governed by n-dimensional static plane symmetric metric.     

AMR Simulations of Magnetohydrodynamic Problems by the CESE Method in Curvilinear Coordinates

The objective of this paper is to present new extensions of the space – time conservation element and solution element (CESE) method for simulations of magnetohydrodynamic (MHD) problems in general curvilinear coordinates by using an adaptive mesh refinement (AMR) grid system. By transforming the governing MHD equations from the physical space (x,y,z) to the computational space (ξ,η,ζ) while retaining the form of conservation, the CESE method is established for MHD in the curvilinear coordinates. Utilizing the parallel AMR package PARAMESH, we present the first implementation of applying the AMR CESE method for MHD (AMR-CESE-MHD) in both Cartesian and curvilinear coordinates. To show the validity and capabilities of the AMR-CESE-MHD code, a suite of numerical tests in two and three dimensions including ideal MHD and resistive MHD are carried out, with two of them in both Cartesian and curvilinear coordinates. Numerical tests show that our results are highly consistent with those obtained previously by other authors, and the results under both coordinate systems confirm each other very well.     

Interacting Scalar And Spinor Fields In Bianchi Type I Universe Filled With Magneto-Fluid

Self-consistent system of spinor, scalar and BI gravitational fields in presence of magneto-fluid and Λ term is considered. Assuming that the expansion of the BI universe is proportional to the σ₁ component of the shear tensor, exact solutions for the metric functions, as well as for scalar and spinor fields are obtained. For a non-positive Λ, the initially anisotropic space–time becomes isotropic one in the process of expansion; whereas for Λ > 0, an oscillatory mode of expansion of the BI model occurs. PACS numbers: 03.65.Pm and 04.20.Ha     

Fluctuations of Solar Activity during the Declining Phase of the 11-Year Sunspot Cycle

The number of coronal mass ejections (CMEs) erupting from the Sun follows a trend similar to that of sunspot numbers during the rising and maximum phase of the solar cycle. In the declining phase, the CME number has large fluctuations, dissimilar to those of sunspot numbers. In several studies of solar – interplanetary and solar – terrestrial relationships, the sunspot numbers and the 2800-MHz flux (F10) are used as representative of solar activity. In the rising phase, this may be adequate, but in the declining phase, solar parameters such as CMEs may have a different behaviour. Cosmic-ray Forbush decreases may occur even when sunspot activity is low. Therefore, when studying the solar influence on the Earth, one has to consider that although geomagnetic conditions at solar maximum will be disturbed, conditions at solar minimum may not be necessarily quiet.     

<Emphasis Type="Italic">N</Emphasis>-dimensional Bianchi type-I universe in creation-field cosmology

We have studied the Hoyle-Narlikar C-field cosmology with Bianchi type-I space–time in N dimensions. Using methods of Narlikar and Padmanabham (Phys. Rev. D 32:1928, 1985), the solutions have been studied when the creation field C is a function of time t only. The geometrical and physical aspects for the model are also studied.     

Resolving the Degeneracy: Experimental Tests of the New Self Creation Cosmology and a Heterodox Prediction for Gravity Probe B

The new theory of Self Creation Cosmology has been shown to yield a concordant cosmological solution that does not require inflation, exotic non-baryonic Dark matter or unknown Dark Energy to fit observational constraints. In vacuo there is a conformal equivalence between this theory and canonical General Relativity and as a consequence an experimental degeneracy exists as the two theories predict identical results in the standard tests. However, there are three definitive experiments that are able to resolve this degeneracy and distinguish between the two theories. Here these standard tests and definitive experiments are described. One of the definitive predictions, that of the geodetic precession of a gyroscope, has just been measured on the Gravity Probe B satellite, which is at the present time of writing in the data processing stage. This is the first opportunity to falsify Self Creation Cosmology. The theory predicts a ‘frame-dragging’ result equal to GR but a geodetic precession of only 2/3 the GR value. When applied to the Gravity Probe B satellite, Self Creation Cosmology predicts an E–W gravitomagnetic/frame-dragging precession, equal to that of GR, of 40.9 milliarcsec/yr but a N–S gyroscope (geodetic + Thomas) precession of just 4.4096 arcsec/yr.     

The problem of linking minor meteor showers to their parent bodies: initial considerations

Efforts to link minor meteor showers to their parent bodies have been hampered both by the lack of high-accuracy orbits for weak showers and the incompleteness of our sample of potential parent bodies. The Canadian Meteor Orbital Radar (CMOR) has accumulated over one million meteor orbits. From this large data set, the existence of weak showers and the accuracy of the mean orbits of these showers can be improved. The ever-growing catalogue of near-Earth asteroids (NEAs) provides the complimentary data set for the linking procedure. By combining a detailed examination of the background of sporadic meteors near the orbit in question (which the radar data makes possible) and by computing the statistical significance of any shower association (which the improved NEA sample allows) any proposed shower–parent link can be tested much more thoroughly than in the past. Additional evidence for the links is provided by a single-station meteor radar at the CMOR site which can be used to dispel confusion between very weak showers and statistical fluctuations in the sporadic background. The use of these techniques and data sets in concert will allow us to confidently link some weak streams to their parent bodies on a statistical basis, while at the same time showing that previously identified minor showers have little or no activity and that some previously suggested linkages may simply be chance alignments.     

MIDI – the 10 μm instrument on the VLTI

After more than five years of preparation, the mid-infrared interferometric instrument MIDI has been transported to Paranal where it will undergo testing and commissioning on theVery Large Telescope Interferometer VLTI from the end of 2002through large part of this year 2003. Thereafter it will be available as a user instrument to perform interferometric observations over the8 μm–13 μm wavelength range, with a spatial resolution of typically 20 milliarcsec, a spectral resolution of up to 250, and an anticipated point source sensitivity of N = 3–4 mag or 1–2.5 Jy for self –fringe tracking, which will be the only observing mode during the first months of operation. We describe the layout of the instrument, laboratory tests, and expected performance, both for broadband and spectrally resolved observing modes. We also briefly outline the planned guaranteed time observations. This revised version was published online in July 2006 with corrections to the Cover Date.     

Bianchi type I two-fluid cosmological models with a variable G and Λ

This paper presents anisotropic, homogeneous two-fluid cosmological models in a Bianchi type I space–time with a variable gravitational constant G and cosmological constant Λ. In the two-fluid model, one fluid represents the matter content of the universe and another fluid is chosen to model the CMB radiation. We find a variety of solutions in which the cosmological parameter varies inversely with time t. We also discuss in detail the behavior of associated fluid parameters and kinematical parameters. This paper pictures cosmic history when the radiation and matter content of the universe are in an interactive phase. Here, Ω is closing to 1 throughout the cosmic evolution.      

Physical-mechanical properties of a cometary nucleus

Physical-mechanical properties of cometary nuclei matter are described in detail. As compared to other Solar System bodies, cometary nuclei are characterized by low strength properties. The ultimate tensile strength of cometary matter and cometary nuclei on the whole is about 2 kPa. An analysis performed based on a rheological model of a self-gravitating triaxial solid body showed that cometary nuclei less than 50–60 km (this actually being all known comets) are characterized by a constant ultimate tensile strength which is determined only by the matter composition and structure. The effective ultimate tensile strength for bodies larger than 50–60 km is determined by the body mass and figure parameters and increases according to the quadratic law depending on the body dimensions and mass. Such an increase of the effective strength can explain the absence or deficit of cometary nuclei more than 60 km in size, since it can significantly affect the parameters of the parent body destruction and the formation of a secondary population. The dependence of the mechanism and character of destruction on the parameters of the figure for Kuiper objects more than 50–60 km is size can yield a deficit of the population of the bodies whose figure parameters are a/c > 1.75 with respect to the bodies with a/c < 1.75 figure parameters.     

Active Adaptive Arrays: The ASTRON Approach to SKA

It has been argued, for a number of reasons, that the next generation radio telescope should be a multi-element interferometer with a collecting area of about 1 km². The remaining parameters of such an instrument – frequency range, angular resolution, instantaneous bandwidth, etc. – will be science driven. The requirements for propagation studies are briefly discussed, and it is pointed out how variable-source confusion may differ from the normal variety. Finally, the Dutch project to achieve a large collecting area using adaptive arrays of active antennas is described. A systematic approach has been adopted, with the construction of arrays of increasing complexity to test design features at each state. Recently, development of a low frequency array (LOFAR) has become an additional option. It would facilitate tests of some of the larger instrument's features, and provide real data on the influence of the ionosphere and interfering sources. This revised version was published online in July 2006 with corrections to the Cover Date.