ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    Electronic Resource
    Electronic Resource
    Cosmological models that describe particle creation in the early universe and evolve into the "present-day'' universe (1991)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 32 (1991), S. 3546-3552 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: The disappearance of the cosmological constant can be formally treated by means of similarity solutions of general relativity that evolve from a stage with conformal symmetry to a stage with homothetic symmetry. In this work it is assumed that in this transition the universe does not "lose its memory'' completely, but it does "remember'' some of its past characteristics. Specifically, it is assumed that the equation of state remains the same in both stages. Then, the most general, spherically symmetric, cosmological model compatible with this assumption is developed. It is shown that it can be used to describe, classically, the birth, near the center of a spherical domain (a "bubble'') of positive density and pressure from an early universe with particle production. As a consequence of the difference of pressures, the bubble grows in size and mass and evolves into a present-day FLRW universe with p=nρ. The model, therefore, is of relevance to the description of phase changes typical of inflationary universe models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.529416
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    New analytical models for anisotropic spheres in general relativity (1987)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 28 (1987), S. 1114-1117 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Two new exact analytical solutions to Einstein's field equations representing static fluid spheres with anisotropic pressures are presented. One solution has a maximum value of mass of about 0.42 times the radius of the fluid sphere, dictated by causality and the corresponding values for the surface red shift and the central red shift are 1.58 and 9.03, respectively. The other solution has a maximum mass of about 0.435 times the radius of the fluid sphere and the corresponding red shifts from the surface and from the center are 1.77 and 16.28, respectively. In the low mass limit both solutions reduce to the constant density Schwarzschild interior solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.527557
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Imperfect fluids and repulsive gravitation (1987)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 28 (1987), S. 410-411 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Imperfect fluid sources to the Schwarzschild exterior solution are studied under the assumption that the metric coefficients g00 and g11 of the interior solution satisfy the relation g00 g11=−1. It was found that the core of such a distribution is gravitationally repulsive provided the energy density is positive.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.527675
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 4
    Electronic Resource
    Electronic Resource
    Exact solutions and the effective equation of state in Kaluza–Klein theory (1993)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 34 (1993), S. 4080-4092 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: A generalization of the standard class of solutions in the Kaluza–Klein (4+1) gravity, wherein the spherically symmetric metric depends not only on the radius but also on the extra coordinate, is considered. Two new classes of exact solutions of the empty Kaluza–Klein field equations are given. However, it is known that apparently empty solutions of the (4+1) Kaluza–Klein equations can be interpreted as solutions with effective matter properties of the (3+1) Einstein equations. The physical importance of the new solutions is that in this approach the dependency on the extra coordinate allows us to obtain more general equations of state than before, including ones for radiation, dust, vacuum, and stiff matter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.530028
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 5
    Electronic Resource
    Electronic Resource
    Time-dependent Kaluza–Klein soliton solutions (1993)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 34 (1993), S. 4070-4079 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Time-dependent generalizations of the standard static, spherically symmetric solutions of the empty Kaluza–Klein or (4+1) Einstein equations are considered herein. Such time-dependent solutions exist because Birkhoff's theorem does not hold in (4+1) gravity. The solutions depend on the time and radius but not the fifth or internal coordinate, and fall into four classes with distinct mathematical properties. Physically, some of our solutions represent a static 4D space–time with an oscillating or contracting extra dimension, which suggests their relevance to particle physics. Others represent an expanding 3D space with a contracting extra dimension, which suggests their relevance to cosmology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.530027
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 6
    Electronic Resource
    Electronic Resource
    Kaluza–Klein equations, Einstein's equations, and an effective energy-momentum tensor (1992)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 33 (1992), S. 3883-3887 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Following earlier work, it is inquired how far the 5-D Kaluza–Klein equations without sources may be reduced to the Einstein equations with sources. It is shown by algebraic means that this can be done, provided the extra part of the 5-D geometry is used appropriately to define an effective 4-D energy-momentum tensor. The latter has reasonable properties, but will require further detailed study.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.529834
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 7
    Electronic Resource
    Electronic Resource
    Confined gravitational fields produced by anisotropic fluids (1985)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 26 (1985), S. 2847-2849 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: A family of solutions of the Einstein equations for a spherically symmetric distribution of anisotropic matter is presented, which can be matched with the flat (Minkowskian) space-time on the boundary of the matter, although the energy density and stresses are nonvanishing within the sphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.526710
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 8
    Electronic Resource
    Electronic Resource
    Fluid spheres of uniform density in general relativity (1986)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 27 (1986), S. 271-276 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: A number of exact solutions for spherically symmetric nonstatic fluids of uniform density, surrounded by empty space, are derived and investigated. Solutions that represent expanding and contracting spheres, which tend asymptotically to static configurations described by the Schwarzschild interior solution ( ρ=const), are obtained In some cases the motion of contraction or expansion is reversed, while in other cases there is no bouncing at all. Oscillating solutions are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.527373
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 9
    Electronic Resource
    Electronic Resource
    Perfect fluid spheres admitting a one-parameter group of conformal motions (1985)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 26 (1985), S. 778-784 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Some exact analytical solutions of the Einstein equations for perfect fluids were found under the assumption of spherical symmetry and the existence of a one-parameter group of conformal motions. The first solution exhibited represents a nonstatic homogeneous spherically symmetric distribution of matter which is singular at t=0. Two other solutions represent contracting and expanding fluids, respectively, whose evolution tends asymptotically to a static sphere with a surface gravitational potential equal to (1)/(3) . These two solutions possess vanishing pressure surfaces which are not the boundary of matter except in the static limit. Finally an oscillating distribution of matter is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.526567
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
  • 10
    Electronic Resource
    Electronic Resource
    Isotropic and anisotropic charged spheres admitting a one-parameter group of conformal motions (1985)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 26 (1985), S. 2302-2307 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: Some exact analytical solutions of the static Einstein–Maxwell equations for perfect and anisotropic fluids were found under the assumption of spherical symmetry and the existence of a one-parameter group of conformal motions. All solutions are matched to the Reissner‘xnNordström metric and possess positive energy density larger than the stresses, everywhere within the sphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.526813
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    Paper (German National Licenses)
    Fulltext
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...