Archive

Archive for the ‘4. Astrophysics’ Category

Jun
05

Structure and evolution of a spherical dust star.

1. The modified Oppenheimer-Snyder solution

 Zahid Zakir [1]

Abstract

In the Oppenheimer-Snyder solution (OS) for the parabolic trajectory particle’s worldline r(t,R) in terms of world time t differs from its standard worldline in the Schwarzschild field outside and on the surface of the dust star. This is a consequence of the fact that the trajectory function r(t,R) were defined on the “homogeneity hypersurface”, when r = R at the zero initial moment of proper time in all layers and since these events are not simultaneous, the initial moments of the world time t(R) are nonzero. In view of the fact that the structure of the star at any moment means the determination of the positions of all particles on the hypersurface t=const., and the solution of the OS is used for checking more realistic models of stars, this incompleteness of the procedure for the transition to hypersurface t=const. leads to distortions of physical consequences other models too. A more consistent application of the OS method is proposed, where this problem does not arise. The modification consists in fixing the initial positions r=R for t(R)=0 and determining the shift of the proper time moments in different layers on the hypersurfaces t=const. from the condition of obtaining the standard trajectory function r(t,R). The pictures of particle trajectories of the dust star are presented, which clearly show the internal structure of the star at t=const. At large t, not only the surface asymptotically approaches the gravitational radius, but the world lines of particles in the inner layers also approach their asymptotes, rapidly becoming practically parallel to the world lines of particles at the center and on the surface. This shows that the frozen star picture refers not only to the surface, but also to the inner layers freezing at certain distances from the center.

   PACS: 04.20.Dg;  04.70.-s;  97.60.-s,  98.54.-h

   Keywords: relativistic stars, gravitational collapse, black holes, quark stars

 

Vol. 12, No 1, p. 1 – 16, v1,      June 5, 2017
Electron.: TPAC: 5200-041 v1,    June 5, 2017;             DOI:  10.9751/TPAC.6000-043


[1] Centre for Theoretical Physics and Astrophyics, Tashkent, Uzbekistan  zahidzakir@theor-phys.org

Mar
28

Gravitationally frozen objects and relativistic explosion in general relativity: frozars, frozons and superbursts

 Zahid Zakir [1]

Abstract

 

In general relativity (GR) the worldline of a particle is unique and invariant, proper  time  and world time t are two parametrization of the same events on it only, that leads to a constraint for the proper time moments relating them by t. So, at contraction of a dust shell the proper times at finite t asymptotically freeze by no reaching a moment when the surface could cross the gravitational radius. Processes in entire volume of a star freeze at first at the center, then at higher layers, and at last the surface freezes outside the gravitational radius. Therefore in GR contraction leads to formation not black holes, but frozars (from “frozen star”) with the gravitationally frozen state of matter in entire volume, where the worldlines of particles are time-like everywhere, parallel to the t-axis and each other. Frozar formation in GR is shown for a thin dust shell, a dust ball, a star of uniform density and stars with ultrarelativistic matter. In real stars local temperatures in layers grow faster than temperature on the surface, and the last one grows on t exponentially fast. As high star’s mass, as high probability of that freezing occurs faster than warming up and the frozar will has time to be formed. But at lower masses, when the freezing does not enough fast, the warming up can stop contraction and can lead to explosion. During contraction a significant part of matter appear near the surface where in GR the physical volume sufficiently grows and energy of contraction is transformed to heat with transition of matter to the radiation dominated phase. If the star did not has time to be frozen, the part of ultrarelativistic matter and radiation leaves the star quickly, which appears as relativistic explosion, and the object will observed as relativistic supernova or hypernova. The observed lack of frozars of 2-4 solar mass and flat character of mass spectrum of more massive candidates to frozars confirm these predictions of the theory. the Big Bang and some explosions in astrophysics with large energy release probably are the cases of the relativistic explosion. In the frozar theory it appears a new GR phenomenon, the gravitational crystallization, defining structure of the most compact and massive objects in particle physics, astrophysics and cosmology. Gravitational radius of the system of few frozars sufficiently exceeds the radius of each of them and, therefore, at closing up they will not be able to merge and becomes frozen at distances larger their radii, forming a new state of matter – the gravitational crystal. Frozons, particles of the Planck energy, quantum fluctuations of which are frozen in their self gravitational field, also can not merge, i.e. for frozons there will be no interaction vertexes and they form only clusters and gravitational microcrystals. In astrophysics the supermassive frozen objects in the centers of star clusters, galaxies and quasars are probable gravitational supercrystals from frozars and ordinary matter. Relic frozons and frozar crystals could be the centers of inhomogeneities and also could be appear as a dark matter. If there is the backward contraction, the Universe as whole can be frozen also in the state of a global gravitational crystal which would stop the contraction.

PACS: 04.20.Dg;  04.70.-s;  97.60.-s,  98.54.-h

Keywords: relativistic stars, gravitational collapse, black holes, quark stars

Vol. 10, No 1, p. 41 – 67, v1,     March 28, 2015
Electron.: TPAC: 5200-041 v1,    March 28, 2015 DOI: 10.9751/TPAC.5200-040

Aug
01

Comoving to expansion Newtonian potential of galaxies and clusters instead of dark matter

 Zahid Zakir [1]

Abstract

    Stretching of the Newtonian potential (NP) at early epochs is investigated and it is shown that observed effects, usually ascribed to a dark matter, can by explained by such stretching only. Increasing by time a radius of the gravitationally-bound region (GBR) and conservation of gravitational energy lead to a new scenario in which values of NP in expanding volume are maintained, while in physical volume are stretched. Really, the energy conservation in expanding volume requires for NP values to be comoving to the expanding shells. In addition, the radius of gravitationally-bound region increases by time due to decreasing of expansion velocity and different shells around galaxy cease expansion at different times. Thus, as far a shell placed from galaxy, as longer it was expanded and thickened, while potential difference on its boundaries remained unchanged. This shifts the values of NP around galaxy proportional to the distance r and, as the result, the gravitational acceleration, from NP’s 1/r^2 dependence, turned to 1/r dependence, as for centrifugal acceleration. This fact naturally explains the known empirical facts, such as flatness of rotation curves and velocity-mass relationships for galaxies and velocity dispersion in clusters.

PACS: 95.30.Sf, 95.35.+d, 98.65.Cw, 98.62.Ck
Key words: gravitation, cosmological expasion, rotation curves, galaxy clusters

Vol. 9, No 2, p. 73 –77, v1,          31 July 2014

Online: TPAC: 4960-039 v1,      31 July 2014;   DOI: 10.9751/TPAC.4960-039


[1] Centre for Theoretical Physics and Astrophyics, Tashkent, Uzbekistan  zahidzakir@theor-phys.org

May
06

New effects in cosmology: frequency and intensity stasis for radiation crossed galaxy clusters

 Zahid Zakir [1]

Abstract

     New effects of stasis of radiation due to switching out from expansion flow at crossing largest gravitationally-bound regions (GBR), such as galaxy clusters, are considered and their observational consequences for supernovae and cosmic microwave background (CMB) data are discussed. The stasis of frequency and intensity of radiation at crossing of large number of clusters appreciably decreases observing redshifts z and magnifies apparent luminosities. Only normal redshifts z’ of photons not crossed clusters are directly related with the cosmic scale factor and thus true distances exceed those which follow from z. The effects increase for distant objects because of smaller inter-cluster distances at early epochs. For the relic radiation crossed the clusters the effects lead to the stasis of its temperature and “heating” with respect to a normally expanded flow outside the cluster. As a result, instead of former paradigm about almost sterile propagation of relic radiation from the recombination epoch, there is an opposite picture. Mixing of relic radiation flows, many times isolated from the expansion flow in GBRs along path, leads to their isotropy and loss of earlier perturbations. The observing anisotropy follows from the stasis effects at crossing of multiple layers of clusters at our nearest environment. The stasis effects allow one to do more exact conclusions from data analysis and lead to revising of distances and properties of extragalactic objects.

PACS:  04.20.Cv, 98.80.-k, 98.80.Jk 95.30.Sf, 97.60.Lf, 98.35.Jk, 98.54.-h

Key words: cosmological models, redshift, extra dimension

Vol. 9, No 1, p. 5 – 17, v1,       6 May 2014

Online: TPAC: 4874-035 v1,    6 May 2014;   DOI: 10.9751/TPAC.4874-035


[1] Centre for Theoretical Physics and Astrophyics, Tashkent, Uzbekistan

      zahidzakir@theor-phys.org

May
06

A model of the closed universe gravitating in 4-space

 Zahid Zakir [1]

Abstract

     Models of the closed Universe as a thin  3-sphere in 4-space, gravitating along 3-sphere’s radius, are reformulated in a new form, in which at a local environment of an observer the non-relativistic dynamics of a ball is reproduced with a correct energy conservation condition. Corresponding evolution equations for dust matter and radiation in the 3-sphere are obtained and their observational consequences are studied. It is shown that the closed models in 4-space also lead to the “Miniverse” model with a highly oscillating curve for the “distance modulus – redshift” relation.

PACS:  04.20.Cv, 98.80.-k, 98.80.Jk 95.30.Sf, 97.60.Lf, 98.35.Jk, 98.54.-h

Key words: cosmological models, redshift, extra dimension

Vol. 9, No 1, p. 1 – 4, v1,   6 May 2014

Online: TPAC: 4874-034 v1,  6 May 2014;   DOI: 10.9751/TPAС.4874-034


[1] Centre for Theoretical Physics and Astrophyics, Tashkent, Uzbekistan

      zahidzakir@theor-phys.org

May
15

The closed model of the universe with relativistic redshift

 Zahid Zakir [1]

Abstract

     Starting from the relativistic dynamics of homogeneous expanding ball, a relativistic evolution equation for the closed model of the Universe is formulated which correctly takes into account a relativistic time dilation of proper times due to different expansion speeds at different epochs. The hypersurface of simultaneity of the Universe is spherically-symmetric only in the rest frame of 3-sphere’s centre and, consequently, the evolution is described in world time t of this frame of reference. This relativistic evolution equation coincided with Einstein’s equation for a 3-sphere expanding in 4-space (without dark energy) and has a simple exact solution. There is a relativistic redshift leading to new relation of redshift with the scale factor which then gives new “luminosity-redshift” relation well describing the data for Type 1а supernovae at admissible parameters. By using the initial data – present radius and expansion speed – other properties and evolution of the Universe are predicted. The model predicts that the observing baryon density is one third of total matter density and remaining two third is dark matter density. The accounting of stasis effects slightly changes the parameters only.

  PACS04.20.Cv, 98.80.-k, 98.80.Jk 95.30.Sf, 97.60.Lf, 98.35.Jk, 98.54.-h, 98.80.-k, 04.60.-m  

  Key words: cosmological models, redshift, supernovae, galaxy clusters, dark matter, dark energy  

Vol. 8, No 2, p. 24 – 36, v1,               15 May 2013

Online: TPAC: 4518-030 v1,             15 May 2013; DOI: 10.9751/TPAC.4518-030


[1] Centre for Theoretical Physics and Astrophyics, Tashkent, Uzbekistan

      zahidzakir@theor-phys.org

Apr
15

The frequency and intensity stasis effects for radiation crossed galaxy clusters.

2. Isotropy and anisotropy of CMB

 Zahid Zakir [1]

Abstract

     In the previous two papers it has been studied a new class of general relativistic effects – the frequency and intensity stasis of radiation crossing gravitationally-bound regions (GBRs), such as galaxy clusters, due to switching out from the cosmological expansion flow. In the present paper the theory of stasis effects is applied to cosmic microwave background (CMB). For a part of CMB crossing a cluster these effects lead to the stasis of its temperature and «heating» w.r.t. a normally expanded flow outside the cluster. As a result, instead of former paradigm about almost sterile propagation of CMB from the recombination epoch, in fact, general relativity and cosmological principle lead to the opposite picture. Mixing of flows of relic photons, repitedly isolated many times from expansion flow in GBRs along their path, sufficienly changes the physical characteristics of CMB, particularly, leads to its isotropy and loss of earlier times perturbations. The observing anisotropy follows from the stasis effects at crossing of multiple layers of clusters at our nearest environment.

PACS: 98.80.Es, 97.60.Bw, 98.65.Cw, 98.62.Py, 98.62.Ck, 98.62.Qz, 98.80.Jk, 98.70.Vc

Key words: cosmology, galaxy clusters, gravitation, background radiation, anisotropy  

Vol. 8, No 1, p. 16 –23, v1,  15 April 2013

Online: TPAC: 4488-029 v1,   15 April 2013; DOI: 10.9751/TPAC.4488-029


[1] Centre for Theoretical Physics and Astrophyics, Tashkent, Uzbekistan

      zahidzakir@theor-phys.org

 

Apr
15

 The frequency and intensity stasis effects for radiation crossed galaxy clusters.

1. Localized sources.

 Zahid Zakir [1]

Abstract

     In the previous paper it has been proposed and preliminary studied a new class of general relativistic effects following from switching out of radiation from the cosmological expansion flow at crossing the largest gravitationally-bound regions, such as galaxy clusters. In the present paper more consistent theory of such stasis effects is formulated and its observational consequences are considered, particularly, in this first part of paper the corrections to observational data for Type 1а supernovae are presented. Preservation of frequency and intensity of radiation at crossing large number of clusters leads to sufficient decreasing of observable redshifts z and higher apparent luminosities of sources. Only normal redshifts z’ of photons not crossed clusters, which give true distances exceeding the distances following from z, are directly related with the scale factor. The effects increase for distant objects because of smaller inter-cluster distances at early epochs. The existence of the stasis effects for radiation leads not only to new and more exact data analysis methods in extragalactic astrophysics and cosmology, but also to the revising of distance scales and properties of objects all classes.

PACS: 98.80.Es, 97.60.Bw, 98.65.Cw, 98.62.Py, 98.62.Ck, 98.62.Qz, 98.80.Jk

Key words: cosmology, gravitation, galaxy clusters, supernovae, redshift 

Vol. 8, No 1, p. 7 –15, v1,  15 April 2013

Online: TPAC: 4488-028 v1,   15 April 2013; DOI: 10.9751/TPAC.4488-028


[1] Centre for Theoretical Physics and Astrophyics, Tashkent, Uzbekistan

      zahidzakir@theor-phys.org

 

Apr
15

Redshift stasis of photons at crossing the gravitationally-bound regions revises the supernovae data

 Zahid Zakir [1]

Abstract

     In gravitationally-bound regions (GBR), largest of which are galaxy clusters, metrics is averagely static and here objects, including radiation, do not participate at the cosmological expansion. In the paper the discovery of new observable effects for radiation crossed such regions – the redshift stasis and flux amplification – is reported. The stasis of wavelength appears as a blueshift with respect to a normally expanded flux and the stasis of distances between photons appears as a higher luminosity. Due to smaller inter-cluster distances at earlier epochs, the corrections to observing redshifts and magnitudes grow with distance. It is shown that the influence to the crossing radiation of switching off on expansion flow is significant and it may exceed up to two or three orders the ordinary gravitational effects of clusters. This sufficiently revises the estimations of characteristics of extragalactic objects and the confrontation with observations of cosmological models becomes correct only at accounting of these stasis effects. The stasis effects sufficiently change temperature of cosmic microwave background and its anisotropy also and lead to new blueshift effects, which particularly may appear in observations as a “dark flow”.

PACS: 98.80.Es, 97.60.Bw, 98.65.Cw, 98.62.Py, 98.62.Ck, 98.62.Qz, 98.80.Jk, 98.70.Vc

Key words: cosmology, gravitation, galaxy clusters, supernovae, redshift, background radiation

Vol. 8, No 1, p. 1 – 6, v2,  15 April 2013

Online: TPAC: 4488-027 v1,   15 April 2013; DOI: 10.9751/TPAC.4488-027


[1] Centre for Theoretical Physics and Astrophyics, Tashkent, Uzbekistan

      zahidzakir@theor-phys.org

Jul
01

Dialogues about a fate of stars:

from black holes to frozars

Zahid Zakir [1]

Abstract

    Sagredo and Salviati – two friends of Galilee – almost 400 years ago in Europe disputed about motion of planets, after which the heliocentric system have been understood and accepted almost by all. Their descendants, who were friends too, almost 40 years ago in America, disputed about a gravitational collapse of stars, after which the black holes have been understood and accepted, but not by all. Among not accepted were one of friends and as a result recently their dialogue has been continued in Asia, but already about a choice between black holes and frozars. After that frozars began to be understood and accepted almost by all who had read record of this dialogue and for this reason it is presenting for wider public also.

PACS: 04.20.Dg; 04.70.-s; 97.60.-s, 98.54.-h

relativistic stars, collapse, black holes, supernova, gamma burst, quasars        

Vol. 7, No 2, p. 21 – 37, v1,  1 July 2012

Online: TPAC: 4200-026 v2,  28 September 2012; DOI: 10.9751/TPAC.4200-026


[1] Centre for Theoretical Physics and Astrophyics, Tashkent, Uzbekistan

      zahidzakir@theor-phys.org