Papers

submitted / in press

D. Puetzfeld: The cosmological post-Newtonian equations of hydrodynamics in General Relativity, submitted.

publications

Y.N. Obukhov, D. Puetzfeld: Spinning particles in de Sitter spacetime, Proceedings of the XIV-th Workshop on High Energy Spin Physics DSPIN-11, Dubna, Russia, September 20-24, 2011.

Y.N. Obukhov, D. Puetzfeld: Dynamics of test bodies with spin in de Sitter spacetime, Phys. Rev. D 83 (2011) 044024.

J. Steinhoff, D. Puetzfeld: Multipolar equations of motion for extended test bodies in General Relativity, Phys. Rev. D 81 (2010) 044019.

D. Puetzfeld, Y.N. Obukhov: Motion of test bodies in theories with nonminimal coupling, Phys. Rev. D 78 (2008) 121501.

D. Puetzfeld, Y.N. Obukhov: Probing non-Riemannian spacetime geometry, Phys. Lett. A 372 (2008) 6711.

D. Puetzfeld: The motion of test bodies with microstructure in gauge gravity models, Acta Phys. Pol. B Proc. Supp. 1 (2008) 167.

D. Puetzfeld, Y.N. Obukhov: Propagation equations for deformable test bodies with microstructure in extended theories of gravity, Phys. Rev. D 76 (2007) 084025

D. Puetzfeld: PROCRUSTES: A computer algebra package for post-Newtonian calculations in General Relativity, Comp. Phys. Comm. 175 (2006) 497-508

J. Hwang, H. Noh, D. Puetzfeld: Cosmological nonlinear hydrodynamics with post-Newtonian corrections, J. Cosm. Astrop. Phys. 3 (2008) 10

D. Puetzfeld: Beyond linearized cosmology, Proceedings of the PASCOS 2005 symposium, Gyeongju, Korea, May 30 - June 4 (2005), Eds. K. Choi, J.E. Kim, D. Son, AIP Conference Proceedings 805, (2005) 483-486

D. Puetzfeld: Prospects of non-Riemannian cosmology, Proceedings of the 22nd Texas Symposium on Rel. Astrophysics, Stanford University, December (2004)

D. Puetzfeld: Status of non-Riemannian cosmology, New Astronomy Reviews 49 (2005) 59-64

D. Puetzfeld, X. Chen: Testing non-standard cosmological models with supernovae, Class. Quantum Grav. 21 (2004) 2703-2722

theses

D. Puetzfeld: Building and testing cosmological models: From Friedmann to Weyl-Cartan, PhD. thesis, University of Cologne (2003)

D. Puetzfeld: Exact solutions in metric-affine gauge theory of gravity, Diploma thesis, University of Cologne (2000)

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submitted / in press

The cosmological post-Newtonian equations of hydrodynamics in General Relativity

Dirk Puetzfeld

Abstract: This work represents the first part of a series of papers on a cosmological post-Newtonian formulation of General Relativity. Considering the successful application of weak field approximations of General Relativity in the case of isolated systems our aim is to provide a similar standardized framework for cosmology. Here we work out the cosmological post-Newtonian equations of hydrodynamics up to first post-Newtonian order. The field equations and the equations of motions are explicitly given. We also evaluate one of the standard energy-momentum complexes within our new framework. Our aim is to provide a formulation which closely resembles the commonly used Newtonian form of the cosmological hydrodynamic equations. In addition we discuss several conceptual problems which come with a post-Newtonian cosmological formulation and provide an outlook on the possible implementation of such a formulation in a large-scale structure simulation. In contrast to the linearized versions of General Relativity the post-Newtonian formulation is also valid in the nonlinear regime of gravitational clustering. Therefore, it represents an interesting candidate for bridging the gap between (semi-)analytical calculations in the linear regime and simulations which would require the full apparatus of numerical relativity.

18 pages, submitted

[ preprint available on request ]

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publications

Spinning particles in de Sitter spacetime

Yuri N. Obukhov, Dirk Puetzfeld

Abstract: We report on the multipolar equations of motion for spinning test bodies in the de Sitter spacetime of constant positive curvature. The dynamics of spinning particles is discussed for the two supplementary conditions of Frenkel and Tulczyjew. Furthermore, the 4-momentum and the spin are explicitly expressed in terms of the spacetime coordinates with the help of the 10 Killing vectors available in de Sitter spacetime.

4 pages, Proceedings of the XIV-th Workshop on High Energy Spin Physics DSPIN-11, Dubna, Russia, September 20-24, 2011

[ ps | pdf | gr-qc/1201.2053 ]

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Dynamics of test bodies with spin in de Sitter spacetime

Yuri N. Obukhov, Dirk Puetzfeld

Abstract: We study the motion of spinning test bodies in the de Sitter spacetime of constant positive curvature. With the help of the 10 Killing vectors, we derive the 4-momentum and the tensor of spin explicitly in terms of the spacetime coordinates. However, in order to find the actual trajectories, one needs to impose the so-called supplementary condition. We discuss the dynamics of spinning test bodies for the cases of the Frenkel and Tulczyjew conditions.

10 pages, Phys. Rev. D 83 (2011) 044024, DOI: 10.1103/PhysRevD.83.044024

[ ps | pdf | gr-qc/1010.1451 | Phys. Rev. D server ]

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Multipolar equations of motion for extended test bodies in General Relativity

Jan Steinhoff, Dirk Puetzfeld

Abstract: We derive the equations of motion of an extended test body in the context of Einstein's theory of gravitation. The equations of motion are obtained via a multipolar approximation method and are given up to the quadrupolar order. Special emphasis is put on the explicit construction of the so-called canonical form of the energy-momentum density. The set of gravitational multipolar moments and the corresponding equations of motion allow for a systematic comparison to competing multipolar approximation schemes.

18 pages, Phys. Rev. D 81 (2010) 044019, DOI: 10.1103/PhysRevD.81.044019

[ ps | pdf | gr-qc/0909.3756 | Phys. Rev. D server]

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Motion of test bodies in theories with nonminimal coupling

Dirk Puetzfeld, Yuri N. Obukhov

Abstract: We derive the equations of motion of test bodies for a theory with nonminimal coupling by means of a multipole method. The propagation equations for pole-dipole particles are worked out for a gravity theory with a very general coupling between the curvature scalar and the matter fields. Our results allow for a systematic comparison with the equations of motion of general relativity and other gravity theories.

5 pages, Phys. Rev. D 78 (2008) 121501, DOI: 10.1103/PhysRevD.78.121501

[ ps | pdf | astro-ph/0811.0913 | Phys. Rev. D server]

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Probing non-Riemannian spacetime geometry

Dirk Puetzfeld, Yuri N. Obukhov

Abstract: The equations of motion for matter in non-Riemannian spacetimes are derived via a multipole method. It is found that only test bodies with microstructure couple to the non-Riemannian spacetime geometry. Consequently it is impossible to detect spacetime torsion with the satellite experiment Gravity Probe B, contrary to some recent claims in the literature.

6 pages, 1 figure, Phys. Lett. A 372 (2008) 6711, DOI: 10.1016/j.physleta.2008.09.041

[ ps | pdf | gr-qc/0708.1926 | Phys. Lett. A server ]

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The motion of test bodies with microstructure in gauge gravity models

Dirk Puetzfeld

Abstract: We report on the explicit form of the equations of motion of pole-dipole particles for a very large class of gravitational theories. The non-Riemannian framework in which the equations are derived allows for a unified description of nearly all known gravitational theories. The propagation equations are obtained with the help of a multipole expansion method from the conservation laws that follow from Noether's theorem. The well-known propagation equations of general relativity, e.g., as given by Mathisson and Papapetrou, represent a special case in our general framework. Our formalism allows for a direct identification of the couplings between the matter currents and the gravitational field strengths in gauge gravity models. In particular, it illustrates the need for matter with microstructure for the detection of non-Riemannian spacetime geometries.

6 pages, Acta Phys. Pol. B Proc. Supp. 1 (2008) 167, Based on a presentation given at: "Myron Mathisson: his life, work, and influence on current research", Stefan Banach International Mathematical Center, Warsaw, Poland, 18 -- 20 October, 2007

[ ps | pdf | gr-qc/0904.0362 | Acta Phys. Pol. B server ]

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Propagation equations for deformable test bodies with microstructure in extended theories of gravity

Dirk Puetzfeld, Yuri N. Obukhov

Abstract: We derive the equations of motion in metric-affine gravity by making use of the conservation laws obtained from Noether's theorem. The results are given in the form of propagation equations for the multipole decomposition of the matter sources in metric-affine gravity, i.e., the canonical energy-momentum current and the hypermomentum current. In particular, the propagation equations allow for a derivation of the equations of motion of test particles in this generalized gravity theory, and allow for direct identification of the couplings between the matter currents and the gauge gravitational field strengths of the theory, namely the curvature, the torsion, and the nonmetricity. We demonstrate that the possible non-Riemannian spacetime geometry can only be detected with the help of the test bodies that are formed of matter with microstructure. Ordinary gravitating matter, i.e., matter without microscopic internal degrees of freedom, can probe only the Riemannian spacetime geometry. Thereby, we generalize previous results of General Relativity and Poincare gauge theory.

26 pages, Phys. Rev. D 76 (2007) 084025, DOI: 10.1103/PhysRevD.76.084025

[ ps | pdf | gr-qc/0707.2819 | Phys. Rev. D. server ]

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PROCRUSTES: A computer algebra package for post-Newtonian calculations in General Relativity

Dirk Puetzfeld

Abstract: We report on a package of routines for the computer algebra system Maple which supports the explicit determination of the geometric quantities, field equations, equations of motion, and conserved quantities of General Relativity in the post-Newtonian approximation. The package structure is modular and allows for an easy modification by the user. The set of routines can be used to verify hand calculations or to generate the input for further numerical investigations.

20 pages, 3 figures, Comp. Phys. Comm. 175 (2006) 497-508, DOI: 10.1016/j.cpc.2006.07.003

[ pdf | gr-qc/0610081 | Comp. Phys. Comm. Server]

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Cosmological nonlinear hydrodynamics with post-Newtonian corrections

Jai-chan Hwang, Hyerim Noh, Dirk Puetzfeld

Abstract: The post-Newtonian (PN) approximation, based on the assumptions of weak gravitational fields and slow motions, provides a way to estimate general relativistic effects in the fully nonlinear evolution stage of the large-scale cosmic structures. We extend Chandrasekhar's first order PN (1PN) hydrodynamics based on the Minkowski background to the Robertson-Walker background. We assume the presence of Friedmann's cosmological spacetime as a background. In the background we include the three-space curvature, the cosmological constant and general pressure. In the Newtonian order and 1PN order we include general pressure, stress, and flux. The Newtonian hydrodynamic equations appear naturally in the 0PN order. The spatial gauge degree of freedom is fixed in a unique manner and the basic equations are arranged without taking the temporal gauge conditi on. In this way we can conveniently try alternative temporal gauge conditions. We investigate a number of temporal gauge conditions under which all the remaining variables are equivalently gauge-invariant. Our aim is to present the fully nonlinear 1PN equations in a form suitable for implementation in conventional Newtonian hydrodynamic simulations with minimal extensions. The 1PN terms can be considered as relativistic corrections added to the well known Newtonian equations. The proper arrangement of the variables and equations in combination with suitable gauge conditions would allow the possible future 1PN cosmological simulations to become more tractable. Our equations and gauges are arranged for that purpose. We suggest ways of controlling the numerical accuracy. The typical 1PN order terms are about $10^{-6} \sim 10^{-4}$ times smaller than the Newtonian terms.

26 pages, J. Cosm. Astrop. Phys. 3 (2008) 10, DOI:10.1088/1475-7516/2008/03/010

[ ps | pdf | astro-ph/0507085 | J. Cosm. Astrop. Phys. Server ]

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Beyond linearized cosmology

Dirk Puetzfeld

Abstract: We comment on the necessity of a unified approximative scheme within relativistic cosmology which would allow us to classify different cosmological models in a systematic way. We also report on recent progresses in formulating a cosmological post-Newtonian approximation and the problems related to such a scheme.

4 pages, 2 figures, Proceedings of the PASCOS 2005 symposium, Gyeongju, Korea, May 30 - June 4 (2005), Eds. K. Choi, J.E. Kim, D. Son, AIP Conference Proceedings 805 (2005) 483-486, DOI: 10.1063/1.2149761

[ pdf | astro-ph/0509398 | Am. Inst. Phys. Server ]

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Prospects of non-Riemannian cosmology

Dirk Puetzfeld

Abstract: In this work we provide the motivation for considering non-Riemannian models in cosmology. Non-Riemannian extensions of general relativity theory have been studied for a long time. In such theories the spacetime continuum is no longer described by the metric alone but endowed with additional geometric quantities. These new quantities can be coupled to the intrinsic properties of matter in a very natural way and therefore provide a richer gravitational theory, which might be necessary in view of the recent cosmological evidence for dark matter and dark energy. In this work we mainly focus on th e concepts in metric-affine gravity and point out their possible significance in the process of cosmological model building.

5 pages, 3 figures, Proc. of the 22nd Texas Symposium on Rel. Astrophysics, Stanford University, December (2004)

[ ps | pdf | astro-ph/0501231 | Stanford eConf Server]

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Status of non-Riemannian cosmology

Dirk Puetzfeld

Abstract: We provide a brief chronological guide to the literature on non-Riemannian cosmological models. Developments in this field are traced back to the early seventies and are given in table form.

10 pages, 1 figure, Elsevier preprint style, Proceedings of the 6th UCLA Symposium on "Sources and Detection of Dark Matter and Dark Energy in the Universe", February 18-20, 2004, Marina del Rey, CA, USA, New Astronomy Reviews 49 (2005) 59-64, DOI: 10.1016/j.newar.2005.01.022

[ pdf | ps | gr-qc/0404119 | New. Astron. Rev. Server ]

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Complementary constraints from FR IIb radio galaxies\ and X-ray gas mass fractions in clusters on non-standard cosmological models

Dirk Puetzfeld, Martin Pohl, Zong-Hong Zhu

Abstract: We use recent measurements of the dimensionless coordinate distances from Fanaroff-Riley Type IIb radio galaxies and the X-ray gas mass fractions in clusters to constrain the parameters of a non-standard cosmological model. This work complements our recent analysis of the SN Ia data within a non-Riemannian cosmological model. We use two independent data sets to constrain the new density parameter $\Omega_\psi$, which is related to the non-Riemannian structure of the underlying spacetime and supplements the field equations that are very similar to the usual Friedmann equations of general relativity. Thereby we place an upper limit on the presence of non-Riemannian quantities in the late stages of the universe. The numerical results of this work also apply to several anisotropic cosmological models which, on the level of the field equations, exhibit a similar scaling behavior of the density parameters like our non-Riemannian model.

22 pages, 6 figures, aastex preprint style, Astrophys. J. 619 (2005) 657-666, DOI: 10.1086/426665

[ ps | astro-ph/0407204 | Astrophys. J. Server]

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Testing non-standard cosmological models with supernovae

Dirk Puetzfeld, Xuelei Chen

Abstract: In this work we study the magnitude-redshift relation of a non-standard cosmological model. The model under consideration was firstly investigated within a special case of metric-affine gravity (MAG) and was recently recovered via different approaches by two other groups. Apart from the usual cosmological parameters for pressure-less matter $\Omega_{\rm m}$, cosmological constant/dark energy $\Omega_{\lambda}$, and radiation $\Omega_{\rm r}$ a new density parameter $\Omega_\psi$ emerges. The field equations of the model reduce to a system which is effectively given by the usual Friedmann equations of general relativity, supplied by a correction to the energy density and pressure in form of $\Omega_\psi$, which is related to the non-Riemannian structure of the underlying spacetime. We search for the best-fit parameters by using recent SN Ia data sets and constrain the possible contribution of a new dark-energy like component at low redshifts, thereby we put an upper limit on the presence of non-Riemannian quantities in the late stages of the universe. In addition the impact of placing the data in redshift bins of variable size is studied. The numerical results of this work also apply to several anisotropic cosmological models which, on the level of the field equations, exhibit a similar scaling behavior of the density parameters like our non-Riemannian model.

21 pages, 10 figures, IOP preprint style, Class. Quantum Grav. 21 (2004) 2703-2722, DOI: 10.1088/0264-9381/21/11/013

[ ps | gr-qc/0402026 | Class. Quant. Grav. Server]

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A cosmological model in Weyl-Cartan spacetime: II. Magnitude-redshift relation

Dirk Puetzfeld

Abstract: In this second part of our series of articles on alternative cosmological models we investigate the observational consequences for the new Weyl-Cartan model proposed earlier. We review the derivation of the magnitude-redshift relation within the standard FLRW model and characterize its dependence on the underlying cosmological model. With this knowledge at hand we derive the magnitude-redshift relation within our new Weyl-Cartan model. We search for the best-fit parameters by using the combined data set of 92 SNe of type Ia as compiled by Wang, which is based on recent supernova data of Perlmutter et al. and Riess et al. Additionally, we compare our best-fit parameters with the results of several other groups which performed similar analysis within the standard cosmological model as well as in non-standard models.

23 pages, 5 figures, IOP preprint style, Class. Quantum Grav. 19 (2002) 4463-4482, DOI: 10.1088/0264-9381/19/16/316

[ ps | gzipped ps | pdf | gr-qc/0205052 | Class. Quant. Grav. Server ]

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A non-standard cosmological model

Dirk Puetzfeld

Abstract: Short summary of a talk held at the Journees Relativistes, University College Dublin, Ireland. Contains only abstract and a compilation of references.

1 page, Int. J. of Mod. Physics A Vol. 17 No. 20 (2002) 2772, DOI: 10.1142/S0217751X02011990

[ ps | gzipped ps | pdf | Int. J. Mod. Phys. A Server ]

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A cosmological model in Weyl-Cartan spacetime: I. Field equations and solutions

Dirk Puetzfeld

Abstract: In this first article of a series on alternative cosmological models we present an extended version of a cosmological model in Weyl-Cartan spacetime. The new model can be viewed as a generalization of a model developed earlier jointly with Tresguerres. Within this model the non-Riemannian quantities, i.e.\ torsion $T^{\alpha}$ and nonmetricity $Q_{\alpha \beta}$, are proportional to the Weyl 1-form. The hypermomentum $\Delta_{\alpha \beta}$ depends on our ansatz for the nonmetricity and vice versa. We derive the explicit form of the field equations for different cases and provide solutions for a broad class of parameters. We demonstrate that it is possible to construct models in which the non-Riemannian quantities die out with time. We show how our model fits into the more general framework of metric-affine gravity (MAG).

20 pages, 2 figures, IOP preprint style, Class. Quantum Grav. 19 (2002) 3263-3280, DOI: 10.1088/0264-9381/19/12/310

[ ps | gzipped ps | pdf | gr-qc/0111014 | Class. Quant. Grav. Server ]

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A cosmological model in Weyl-Cartan spacetime

Dirk Puetzfeld, Romualdo Tresguerres

Abstract: We present a cosmological model for early stages of the universe on the basis of a Weyl-Cartan spacetime. In this model, torsion $T^{\alpha}$ and nonmetricity $Q_{\alpha \beta}$ are proportional to the vacuum polarization. Extending earlier work of one of us (RT), we discuss the behaviour of the cosmic scale factor and the Weyl 1-form in detail. We show how our model fits into the more general framework of metric-affine gravity (MAG).

19 pages, 5 figures, IOP preprint style, Class. Quantum Grav. 18 (2001) 677-693, DOI: 10.1088/0264-9381/18/4/308

[ ps | gzipped ps | pdf | gr-qc/0101050 | Class. Quant. Grav. Server ]

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An exact plane-fronted wave solution in metric-affine gravity

Dirk Puetzfeld

Abstract: We study plane-fronted electrovacuum waves in metric-affine gravity (MAG) with cosmological constant in the triplet ansatz sector of the theory. Their field strengths are, on the gravitational side, curvature $R_{\alpha}{}^{\beta}$, nonmetricity $Q_{\alpha\beta}$, torsion $T^{\alpha}$ and, on the matter side, the electromagnetic field strength $F$. Here we basically present, after a short introduction into MAG and its triplet subcase, the results of earlier joint work with Garcia, Macias, and Socorro. Our solution is based on an exact solution of Ozsvath, Robinson, and Rozga describing type N gravitational fields in general relativity as coupled to electromagnetic null-fields.

10 pages, LaTeX 2e, Invited lecture at a Conference in honour of Heinz Dehnen's 65th and Dietrich Kramer's 60th birthday." Held at CINVESTAV-IPN, Mexico City, 2-6 October 2000. To appear in: ``Exact solutions and scalar field in gravity: Recent Developments." A. Macias, J. Cervantes, and C. Laemmerzahl eds., Kluwer, Dordrecht (2001) to be published.

[ ps | gzipped ps | pdf | gr-qc/0011116 ]

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Plane-fronted waves in metric-affine gravity

Alberto Garcia, Alfredo Macias, Dirk Puetzfeld, Jose Socorro

Abstract: We study plane-fronted electrovacuum waves in metric-affine gravity theories (MAG) with cosmological constant. Their field strenghts are, on the gravitational side, curvature $R_{\alpha}{}^{\beta}$, nonmetricity $Q_{\alpha\beta}$, torsion $T^{\alpha}$ and, on the matter side, the electromagnetic field strength $F$. Our starting point is the work by Ozsvath, Robinson, and Rozga on type N gravitational fields in general relativity as coupled to null electromagnetic fields.

20 pages, RevTeX preprint style, published in Physical Review D 62 (2000) 044021, DOI: 10.1103/PhysRevD.62.044021

[ ps | gzipped ps | pdf | gr-qc/0005038 | Phys. Rev. D Server ]

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theses

Building and testing cosmological models: From Friedmann to Weyl-Cartan

Dirk Puetzfeld

Abstract: In this thesis we build and test cosmological models within an alternative gravity theory. Triggered by a wealth of new observational data, there has been a great leap forward to what is nowadays summarized under the name cosmological standard model. Experiments of cosmological interest range from measurements of the cosmic microwave background (COBE, BOOMERANG, MAXIMA, WMAP), the observation of type Ia supernovae (SCP, HIGH-z Search Team), the determination of light element abundances, to surveys mapping the large-scale distribution of luminous matter in the universe (SDSS, 2dFGRS, XMM-LSS). These experiments allow us to test different cosmological models and to put constraints on the parameters within these models. From a theoretical point of view these measurements raise several interesting questions: What is the nature of the so-called dark energy? Is a high amount of dark energy compatible with the other cosmological tests? Are there cosmological models that do not require concepts like dark energy? This brings us to the aim of this work, i.e., to build and test alternative cosmological scenarios. In contrast to the cosmological standard model, which is based on General Relativity (GR), we try to construct viable models within the realm of the so-called metric-affine theory of gravity (MAG) that is no longer tied to a pseudo-Riemannian spacetime structure. Within this theory there are new geometrical quantities, namely torsion and nonmetricity that act as additional field strengths similarly to the curvature in the general relativistic case. From an observational point of view the status of MAG based cosmological models is rather vague. Hence one of the main aims of this work is to obtain quantitative estimates for the parameters in such models. We provide an overview of the standard model of cosmology and introduce all of the important cosmological parameters. Especially, we thoroughly discuss two different cosmological tests, the so-called magnitude-redshift relation and the primordial synthesis of helium. We put special emphasis on the discussion of the parameter dependency of these tests and sketch the current observational situation. Additionally, we provide an overview of the field equations of MAG and the geometric quantities therein, thereby we discuss two interesting special cases of MAG. The first one is the so-called triplet ansatz by which the theory becomes effectively equivalent to the Einstein-Proca theory. The second one is represented by the Weyl-Cartan spacetime for which the traceless part of the nonmetricity vanishes and the symmetric part of the curvature is reduced to its trace part. We report on currently available non-standard cosmological scenarios and present a new cosmological model in Weyl-Cartan spacetime. We derive the field equations of this model, search for exact solutions, and work out the magnitude-redshift relation. Subsequently, we perform a numerical analysis of the SN Ia data within the cosmological standard model and the alternative scenario. Thereby, we constrain the parameters within both models. In particular we obtain a numerical bound on the non-Riemannian contribution to the total density of the universe. The comparison of this result to the primordial helium abundance, which we infer from a semi-analytical nucleosynthesis calculation, enables us to put a very strong quantitative limit on the model parameters.

175 pages, 28 figures, PhD. thesis, University of Cologne (2003)

[ pdf ]

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Exact solutions in metric-affine gauge theory of gravity

Dirk Puetzfeld

Introduction: This thesis is concerned with the search for exact solutions in metric-affine gauge theory of gravity (MAG). The MAG represents a gauge theoretical formulation of a theory of gravity which, in contrast to the theory of General Relativity (GR), is no longer confined to a pseudo-Riemannian spacetime structure. There are new geometric quantities emerging in this theory, the so-called torsion and nonmetricity which act as additional field strengths comparable to the curvature in the general relativistic case. It should be noticed that there are several alternative gravity theories included in MAG, e.g. the Einstein-Cartan theory where the nonmetricity vanishes and the only surviving post-Riemannian quantity is given by the torsion. One expects that the MAG provides the correct description for early stages of the universe, i.e. at high energies, at which the general relativistic description breaks down. In case of vanishing post-Riemannian quantities the MAG proves to be compatible with GR. In contrast to GR there are presently only a few exact solutions available in MAG, what could be ascribed to the complexity of this theory.

121 pages, 5 figures, Diploma thesis, University of Cologne (2000)

[ ps | gzipped ps | pdf ]

stuff that might be of interest

Short exposition on the use of CA systems and cosmology (in german, appears in the RRZK report 2001) [ html | gzipped ps ]