arXiv subjects

Alexander Unzicker

Publications and source records attributed to Alexander Unzicker.

16 recordsLinked to original sources

arXiv2015

A Machian Version of Einstein's Variable Speed of Light Theory

It is a little known fact that while he was developing his theory of general relativity, Einstein's initial idea was a variable speed of light theory. Indeed space-time curvature can be mimicked by a speed of light $c(r)$ that depends on the distribution of masses. Einstein's 1911 theory was considerably improved by Robert Dicke in 1957, but only recently has the equivalence of the variable speed of light approach to the conventional formalism been demonstrated (Broekaert, 2008). Using Green's functions, we show that Einstein's 1911 idea can be expressed in an analytic form, similar to the Poisson equation. Using heuristic arguments, we derive a simple formula that directly relates curvature $w$ to the local speed of light, $w= -c^2 Δ\frac{1}{c^2}$. In contrast to the conventional formulation, this allows for a Machian interpretation of general relativity and the gravitational constant $G$. Gravity, though described by local equations, has its origin in all other masses in the universe.

physics.gen-ph↗

arXiv2011

Do Galaxies Change in Size ? An Angular Size Test at Low Redshift with SDSS Data

Based on magnitudes and Petrosian radii from the Sloan Digital Sky Survey (SDSS, data release 7) at low redhift (z <0.2), we developed a test of galaxy-size evolution. For this first quantitative size analysis using SDSS data, several possible sources of systematic errors had to be considered. The Malmquist bias is excluded by volume-limited samples. A correction for seeing has been developed and applied. We compare different methods to perform the K-correction, and avoid selection effects due to different filters. It is found that apparent average galaxy size slightly decreases with redshift z, corresponding to a growth in time. The effect is smaller for a lower H0, and at the same time less pronounced at higher redshifts, but persists in both cases. Although there is no systematic variation with galaxy luminosity, we took into account the recently discovered luminosity evolution with redshift. Assuming this effect of unknown origin to be real, we find a slight increase of galaxy size with z. The relative change of average size with z usually amounts to less than one half of the respective increase of wavelengths due to the cosmological redshift, making a cosmological interpretation difficult. While the effect shows clear statistical significance, unknown systematics cannot be excluded. In any case, the enigmatic observations of size and luminosity evolution need to be analysed together. To facilitate further investigations, a complete Mathematica code and instructions for data download are provided.

physics.gen-ph↗

arXiv2010

Immanuel Kant on Supersymmetry: A Practical Evaluation

A short review of the motivations for supersymmetry in astrophysics and particle physics is given. Despite the amount of theoretical research conducted in the past decades, no observational evidence for supersymmetry has yet been found. While a large part of the community is expecting supersymmetry to be discovered in the Large Hadron Collider (LHC), some of the basic arguments in favor are disputed here. Since it is not excluded that the author's view may be biased by his research, he proposes a bet on the discovery of supersymmetric particles: According to the philosopher Immanuel Kant, the bet marks the difference between persuasion and conviction.

physics.gen-ph↗

arXiv2009

How to Determine the Probability of the Higgs Boson Detection

The Higgs boson is the most important, though yet undiscovered ingredient of the standard model of particle physics. Its detection is therefore one of the most important goals of high energy physics that can guide future research in theoretical physics. Enormous efforts have been undertaken to prove the existence of the Higgs boson, and the physics community is excitedly awaiting the restart of the Large Hadron Collider at CERN. But how sure can we be that the Higgs exits at all? The German philosopher Immanuel Kant recommended betting at such controversial questions, and Stephen Hawking announced a $100 bet against the Higgs. But seriously, online prediction markets, which are a generalized form of betting, do provide the best possible probability estimates for future events. It is proposed that the scientific community uses this platforms for evaluation. See also an online description www.Bet-On-The-Higgs.com.

physics.gen-ph↗

arXiv2008

A Look at the Abandoned Contributions to Cosmology of Dirac, Sciama and Dicke

The separate contributions to cosmology of the above researchers are revisited and a cosmology encompassing their basic ideas is proposed. We study Dirac's article on the large number hypothesis (1938), Sciama's proposal of realizing Mach's principle (1953), and Dicke's considerations (1957) on a flat-space representation of general relativity with a variable speed of light (VSL). Dicke's tentative theory can be formulated in a way which is compatible with Sciama's hypothesis on the gravitational constant G. Additionally, such a cosmological model is shown to satisfy Dirac's second `large number' hypothesis on the total number of particles in the universe being proportional to the square of the epoch. In the same context, Dirac's first hypothesis on an epoch-dependent G-contrary to his prediction- does not necessarily produce a visible time dependence of G. While Dicke's proposalreproduces the classical tests of GR in first approximation, the cosmological redshift is described by a shortening of measuring rods rather than an expansion of space. Since the temporal evolution of the horizon R is governed by \dot R(t) =c(t), the flatness and horizon problems do not arise in the common form.

physics.gen-ph↗

arXiv2008

Why do we Still Believe in Newton's Law ? Facts, Myths and Methods in Gravitational Physics

An overview of the experimental and observational status in gravitational physics is given, both for the known tests of general relativity and Newtonian gravity, but also for the increasing number of results where these theories run into problems, such as for dark matter, dark energy, and the Pioneer and flyby anomalies. It is argued that (1) scientific theories should be tested (2) current theories of gravity are poorly tested in the weak-acceleration regime (3) the measurements suggest that the anomalous phenomena have a common origin (4) it is useful to consider the present situation under a historical perspective and (5) it could well be that we still do not understand gravity. Proposals for improving the current use of scientific methods are given. `We do not know anything - this is the first. Therefore, we should be very modest - this is the second. Not to claim that we do know when we do not - this is the third. That's the kind of attitude I'd like to popularize. There is little hope for success.' (Karl Popper)

gr-qc↗

arXiv2008

A Quick Verification of the 2-D Galaxy Distribution with SDSS Data

We present source code for the computer algebra system Mathematica that analyzes the distribution of nearby Galaxies using SDSS data. Download instructions are given, thus within 10 minutes, the reader can verify that galaxies are distributed in an essentially non-homogeneous manner and cluster on 2-dimensional structures. The short code uses a simple method inspired by Minkowski functionals: the distances to the next neighbors are calculated and compared to random distributions in three and two dimensions. The observed distance distribution corresponds clearly to the latter case. The paper may also be helpful for nonexpert scientists to get started with SDSS data analysis.

astro-ph↗

arXiv2007

Mach's Principle and a Variable Speed of Light

Ernst Mach (1838-1916) suggested that the origin of gravitational interaction could depend on the presence of all masses in the universe. A corresponding hypothesis of Sciama (1953) on the gravitational constant, c^2/G = \sum m_i/r_i, is linked to Dicke's (1957) proposal of an electromagnetic origin of gravitation, a precursor of scalar-tensor-theories. In this an equivalent description in terms of a variable speed of light (VSL) is given, and the agreement with the four classical tests of general relativity is shown. Moreover, VSL opens the possibility to write the total energy of a particle as E=mc^2; this necessarily leads to the proportionality of inertial and gravitating mass, the equivalence principle. Furthermore, a formula for c depending on the mass distribution is given that reproduces Newton's law of gravitation. This mass distribution allows to calculate a slightly variable term that corresponds to the `constant' G. The present proposal may also supply an alternative explanation to the flatness problem and the horizon problem in cosmology.

gr-qc↗

arXiv2007

The VSL Discussion: What Does Variable Speed of Light Mean and Should we be Allowed to Think About ?

In the past years, variable speed of light (VSL) theories have been of growing interest but also a subject of controversial discussion. They have been accused both for tautologies and for violating special relativity, and concerns have been expressed about the validity of such approaches in general (e.g. Ellis, astro-ph/0703751). Without trying completeness on the issue, the example of Einstein's VSL attempts (1911) and Dicke's `electromagnetic' theory (1957) are urges to give some comments on the above criticism.

physics.gen-ph↗

arXiv2007

A Quick and Dirty Approach to Verify the Pioneer Anomaly

We present source code for the computer algebra system Mathematica that analyzes the motion of the Pioneer spacecraft using the public available ephemeris data from JPL's website. Within 15 minutes, the reader can verify that the Pioneer anomalous acceleration a_p (1) exists in the order of magnitude of c H_0, (2) is not due to mismodeling of gravitational attraction, solar pressure or spacecraft attitude maneuvers. The simple code of about 100 lines may easily be extended by the reader to include further tests. Due to the limitations of our approach, we do not know (1) whether the unknown raw data were correctly processed to generate the trajectory files (2) how the apparent mismatch of ephemerides before 1990 had occurred.

gr-qc↗

arXiv2006

A Solar System Test of Mach's Principle with Gravimetric Data

We present a new test for a possible Mach-Sciama dependence of the Gravitational constant G. According to Ernst Mach (1838-1916), the gravitational interaction depends on the distribution of masses in the universe. A corresponding hypothesis of Sciama (1953) on the gravitational constant, $c^2/G = \sum m_i/r_i$, can be tested since the elliptic earth orbit should then cause minute annual variations in G. The test is performed by analyzing the gravity signals of a network of superconducting gravimeters (SG) which reach a precision of $10^{-10} m/s^2$. After reducing the signal by modelling tidal, meteorologic and geophysical effects, no significant evidence for the above dependence is found.

gr-qc↗

arXiv2005

Translation of Einstein's Attempt of a Unified Field Theory with Teleparallelism

We present the first English translation of Einstein's original papers related to the teleparallel ('absolute parallelism', 'distant parallelism' and the German 'Fernparallelismus' are synonyms) attempt of an unified field theory of gravitation and electromagnetism. Our collection contains the summarizing paper in Math. Annal. 102 (1930) pp. 685-697 and 2 reports published in 'Sitzungsberichte der Preussischen Akademie der Wissenschaften' on June 7th, 1928 (pp. 217-221), June 14th, 1928 (pp. 224-227) and a precursor report (July 9th, 1925 pp. 414-419). To ease understanding, literature on tensor analysis is quoted in the footnotes.

physics.hist-ph↗

arXiv2003

Galaxies as Rotating Buckets - a Hypothesis on the Gravitational Constant Based on Mach's Principle

According to Mach's principle inertia has its reason in the presence of all masses in the universe. Despite there is a lot of sympathy for this plausible idea, only a few quantitative frameworks have been proposed to test it. In this paper a tentative theory is given which is based on Mach's critisism on Newton's rotating bucket. Taking this criticism seriously, one is led to the hypothesis that the rotation of our galaxy is the reason for gravitation. Concretely, a functional dependence of the gravitational constant on the size, mass and angular momentum of the milky way is proposed that leads to a spatial, but not to a temporal variation of G. Since Newton's inverse-square law is modified, flat rotation curves of galaxies can be explained that usually need the postulate of dark matter. While the consequences for stellar evolution are discussed briefly, a couple of further observational coincidences are noted and possible experimental tests are proposed.

gr-qc↗

arXiv2003

Displacement Field and Elastic Energy of a Circular Twist Disclination for Large Deformations - an Example how to Treat Nonlinear Boundary Value Problems with Computer Algebra Systems

A circular twist disclination is a nontrivial example of a defect in an elastic continuum that causes large deformations. The minimal potential energy and the corresponding displacement field is calculated by solving the Euler-Lagrange-equations. The nonlinear incompressibility constraint is rigorously taken into account. By using an appropriate curvilinear coordinate system a finer resolution in the regions of large deformations is obtained and the dimension of the arising nonlinear PDE's is reduced to two. The extensive algebraic calculations that arise are done by a computer algebra system (CAS). The PDE's are then solved by a difference scheme using the Newton-Raphson algorithm of successive approximations for multidimensional equations. Additional features for global convergence are implemented. To obtain basic states that are sufficiently close to the solution, a one dimensional linearized version of the equation is solved with a numerical computation that reproduces the analytical results of Huang and Mura (1970). With this method, rigorous solutions of the nonlinear equations without any additional simplifications can be obtained. The numerical results show a contraction of the singularity line which corresponds to the well-known Poynting effect in nonlinear elasticity. This combination of analytical and numerical computations proves to be a versatile method to solve nonlinear boundary value problems in complicated geometries.

cond-mat.mtrl-sci↗

arXiv2000

What can Physics learn from Continuum Mechanics ?

This paper is mostly a collection of ideas already published by various authors, some of them even a long time ago. Its intention is to bring the reader to know some rather unknown papers of different fields that merit interest and to show some relations between them the author claims to have observed. In the first section, some comments on old unresolved problems in theoretical physics are collected. In the following, I shall explain what relation exists between Feynman graphs and the teleparallel theory of Einstein and Cartan in the late 1920s, and the relation of both to the theories of the incompressible aether around 1840. Reviewing these developments, we will have a look at the continuum theory of dislocations developed by Kroener in the 1950s and some techniques of differential geometry and topology relevant for a modern description of defects in continous media. I will then illustrate some basic concepts of nonlinear continuum mechanics and discuss applications to the above theories. By doing so, I hope to attract attention to the possible relevance of these facts for `fundamental' physics.

gr-qc↗

arXiv1997

Teleparallel Space-Time with Defects yields Geometrization of Electrodynamics with quantized Charges

In the present paper a geometrization of electrodynamics is proposed which makes use of a generalization of Riemannian geometry considered already by Einstein and Cartan in the 20ies. Cartan's differential forms description of a teleparallel space-time with torsion is modified by introducing distortion 1-forms which correspond to the distortion tensor in dislocation theory. Under the condition of teleparallelism, the antisymmetrized part of the distorsion 1-form approximates the electromagnetic field, whereas the antisymmetrized part of torsion contributes to the electromagnetic current. Cartan's structure equations, the Bianchi identities, Maxwell's equations and the continuity equation are thus linked in a most simple way. After these purely geometric considerations a physical interpretation, using analogies to the theory of defects in ordered media, is given. A simple defect, which is neither a dislocation nor disclination proper, appears as source of the electromagnetic field. Since this defect is rotational rather than translational, there seems to be no contradiction to Noether's theorem as in other theories relating torsion to electromagnetism. Then,congruences of defect properties and quantum behaviour that arise are discussed, supporting the hypothesis that elementary particles are topological defects of space-time. In agreement with the differential geometry results, a dimensional analysis indicates that the physical unit (lenght)^2 rather than As is the appropriate unit of the electric charge.

gr-qc↗