M. Heyl’s research while affiliated with German Aerospace Center (DLR) and other places

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Publications (17)


New Aspects of Photon Propagation in Expanding Universes
  • Preprint
  • File available

October 2016

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M. Heyl

According to present cosmological views the energy density of CMB (Cosmic Microwave Background) photons, freely propagating through the expanding cosmos, varies proportional to 1/S^4 with S being the scale factor of the universe. This behavior is expected, because General Theory of Relativity, in application to FLRW- (Friedmann-Lemaitre-Robertson-Walker) cosmological universes, leads to the conclusion that the photon wavelengths increase during their free passage through the spacetime metrics of the universe by the same factor as does the scale factor S. This appears to be a reasonable explanation for the presently observed Planckian CMB spectrum with its actual temperature of about 2.7 K, while at the time of its origin after the last scattering during the recombination phase its temperature should have been about 3000 K, at an epoch of about 380 ky after the Big Bang, when the scale of the universe S_r was smaller by roughly a factor of S/S_r = 1+z_r = 1100 compared to the present scale S = S_0 of the universe. In this paper we start from putting the question whether the scale-behavior of the CMB energy density that enters the energy-momentum tensor of the field equations describing the expanding universe is really falling off like 1/S^4 and, if in fact a deviation from a behavior according to 1/S^4 would occur, why do we nevertheless presently observe a CMB energy density which appears to be in accordance with such a 1/S^4-scaling? This question arises from another basic and fundamental question, namely: Can we really assume that the wavelength of the freely propagating photon during its travel all the way along its light geodetic is permanently affected by the expansion of the universe, i.e continuously recognizes the expansion of the cosmic scale S? With other words: Do freely propagating photons ........

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Debye screening under non-equilibrium plasma conditions

March 2016

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57 Reads

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12 Citations

Astronomy and Astrophysics

As has been revealed in a number of more recent astrophysical papers, in most of the tenuous space plasmas Maxwellian distribution functions cannot be expected for ions or electrons because of the lack of efficient relaxation processes. Many of the classical characteristics of plasmas, such as plasma frequency or Debye length, are calculated on the basis of the assumption, however, that Maxwellians prevail, which under most of the relevant astrophysical plasma conditions is not the case. We here therefore consider this specific problem of Debye shieldings of single charges in a plasma for the case of prevailing non-equilibrium distribution functions for ions and electrons. As typical non-equilibrium functions, so-called Kappa functions were considered with clear preference, and we therefore study here the Debye shielding in a plasma with Kappa-distributed electrons and ions. We show that the so-called Debye shielding increases with increasing extent of the high-velocity tail of the electron distribution function, or in other words, with lower Kappa index of the underlying Kappa function. In our calculations we demonstrate that the Debye lengths become enlarged by about a factor of 10 with respect to its classically expexted value if highly suprathermal electron distributions prevail with Kappa indices close to 1.5.


The Thermodynamics of a Gravitating Vacuum

December 2014

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32 Reads

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2 Citations

Physical Science International Journal

In the present days of modern cosmology it is assumed that the main ingredient to cosmic energy presently is vacuum energy with an energy density ϵvac\epsilon_\mathrm{vac} that is constant over the cosmic evolution. In this paper here we show, however, that this assumption of constant vacuum energy density is unphysical, since it conflicts with the requirements of cosmic thermodynamics. We start from the total vacuum energy including the negatively valued gravitational binding energy and show that cosmic thermodynamics then requires that the cosmic vacuum energy density can only vary with cosmic scale R=R(t) according to ϵvacRν\epsilon _\mathrm{vac}\sim R^{-\nu } with only two values of ν\nu being allowed, namely ν1=2\nu _\mathrm{1}=2 and ν2=5/2\nu _\mathrm{2}=5/2. We then discuss these two remaining solutions and find, when requiring a universe with a constant total energy, that the only allowed power index is ν1=2\nu _\mathrm{1}=2. We discuss the consequences of this scaling of ϵvac\epsilon _\mathrm{vac} and show the results for a cosmic scale evolution of a quasi-empty universe like the one that we are presently faced by.


Cosmic vacuum energy decay and creation of cosmic matter

October 2007

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57 Reads

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23 Citations

The Science of Nature

In the more recent literature on cosmological evolutions of the universe, the cosmic vacuum energy has become a nonrenouncable ingredient. The cosmological constant Lambda, first invented by Einstein, but later also rejected by him, presently experiences an astonishing revival. Interestingly enough, it acts like a constant vacuum energy density would also do. Namely, it has an accelerating action on cosmic dynamics, without which, as it appears, presently obtained cosmological data cannot be conciliated with theory. As we are going to show in this review, however, the concept of a constant vacuum energy density is unsatisfactory for very basic reasons because it would claim for a physical reality that acts upon spacetime and matter dynamics without itself being acted upon by spacetime or matter.


About universes with scale-related total masses and their abolition of presently outstanding cosmological problems

February 2007

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25 Reads

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15 Citations

Astronomische Nachrichten

Cosmological consequences of a strictly valid total energy conservation for the whole universe are investigated in this paper. Interestingly enough as one consequence of ergodically behaving universes very specific scaling laws with the diameter R of the universe can be derived for relevant cosmic quantities. Especially the 1/R^2- scaling of mass - and vacuum energy - density then automatically leads to a vanishing cosmic curvature parameter k=0 and also reveals, that for such universes no horizon problem occurs. In addition the longstanding problem of observationally indicated very low cosmic vacuum energies in contrast to the very large quantumfield estimates is easily solved when the vacuum energy density decay with 1/R^2 is taken into account reconciling presently observed vacuum energy density values with those from theoretical expectations. We also suggest why the mass of the universe can permanently increase and can in fact grow up from a Planck mass as a pure vacuum fluctuation. Comment: Accepted by AN, 8 pages


Concerning the instantaneous mass and the extent of an expanding universe

August 2006

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32 Reads

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7 Citations

Astronomische Nachrichten

In this article we want to answer the cosmologically relevant question what, with some good semantic and physical reason, could be called the mass of an infinitely extended, homogeneously matter-filled and expanding universe. To answer this question we produce a space-like sum of instantaneous cosmic energy depositions surrounding equally each spacepoint in the homogeneous universe. We calculate the added-up instantaneous cosmic energy per volume around an arbitrary space point in the expanding universe. To carry out this sum we use as basic metrics an analogy to the inner Schwarzschild metric applied to stars, but this time applied to the spacepoint-related universe. It is then shown that this leads to the added-up proper energy within a sphere of a finite outer critical radius defining the point-related infinity. As a surprise this radius turns out to be reciprocal to the square root of the prevailing average cosmic energy density. The equivalent mass of the universe can then also be calculated and, by the expression which is obtained here, shows a scaling with this critical radius of this universe, a virtue of the universe which was already often called for in earlier works by E.Mach, H.Thirring and F.Hoyle and others. This radius on the other hand can be shown to be nearly equal to the Schwarzschild radius of the so-defined mass of the universe.


Universes with constant total energy: Do they solve important cosmological problems?

January 2006

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18 Reads

We study cosmological consequences of total energy conservation strictly valid for the whole universe. As prime consequence of ergodically behaving universes very specific scaling laws for relevant cosmic quantities with the diameter R of the universe are derived. Especially the R-2 - scaling of mass - and vacuum energy - density directly leads to a vanishing cosmic curvature parameter k = 0 and abolishes for such universes the horizon problem. The longstanding problem of observationally indicated very low cosmic vacuum energies in contrast to the very large quantumfield estimates now is easily solved when the vacuum energy density decay with R-2 is taken into account.


Citations (12)


... The explanation for this cosmological behavior in the framework of general relativity requires assuming that a considerable part of the universe consists of a hypothetical dark energy with a negative pressure component [2].Many authors have suggested that this dark energy is a cosmic fluid parameterized by an equation of state ω = p/ρ < -1/3 where p is the spatially homogeneous pressure and ρ is the dark energy density [1,2,3,4,5]. Redshifts of distant supernovae SN-Ia measurements have made astrophysicists to surmise universe as showing an accelerated expansion with a coasting universe reminiscent of a vanishing cosmic mass density [6], while recent Hubble tension measurements have posited dynamical dark energy [7]. The range for which ω< -1 has been denoted as phantom energy and possesses peculiar properties, such as negative temperatures and the energy density which increases to infinity in a finite time, resulting in a big rip [2,3,4]. ...

Reference:

A Theoretical Model of Dark Energy Stars in Einstein-Gauss-Bonnet Gravity
A universe with a constant expansion rate
  • Citing Article
  • August 2020

Physics & Astronomy International Journal

... Actually, the exponential cut-off of kappa distribution reduced the super luminal particles to the velocity momentum. Another way to turn down the abundances of particles with velocities larger than that of light to zero is through a relativistically modified kappa function [54] where the properties of velocity moments for < 3∕2 needs further exploration. ...

Suprathermal plasma distribution functions with relativistic cut-offs
  • Citing Article
  • January 2020

Monthly Notices of the Royal Astronomical Society

... The results mentioned above were obtained by fitting the Voyager/Low-Energy Charged Particle (LECP) electron observations at energies 20 keV using a single isotropic kappa distribution function. Further theoretical analysis of kappa distributions has been carried out recently by Fahr & Dutta-Roy (2019), Scherer et al. (2019), and Fahr & Heyl (2020). Since electrons below 20 keV were not measured, another possible scenario is that the bulk electrons in the IHS have properties similar to those of thermal protons, and that suprathermal electrons do not contribute significantly to the pressure. ...

Probing the thermodynamic conditions of the heliosheath plasma by shock wave propagation
  • Citing Article
  • August 2020

Astronomy and Astrophysics

... From this star-correlation function ( ) l ξ we will deduce in the following an associated model for the underlying cosmic matter density distribution ( ). U U l ρ ρ = This we first did for a different aspect in a recent paper Fahr etal., 32 . We use the well confirmed correlation function ( ) l ξ based on astronomical observations of the visible star and galaxy constellation which is surrounding us seen from our cosmic vantage point, -and, according to the generally assumed cosmological principle, also should surround every other cosmic vantage point in an analogous and equivalent manner, unless the generally accepted, sacrosanct cosmological principle would turn out to be violated,-in which case, however, all the other Robertson-Walker cosmologies would as well become invalid, and even taken broader, all cosmology had to be given up. ...

Stellar matter distribution with scale-invariant hierarchical structuring
  • Citing Article
  • July 2019

Physics & Astronomy International Journal

... Such confidence is somehow based on the undoubted success of GR in our immediate spatial environment, with or without a Λ-term which has been termed "dark energy," whose necessity is still debated. There is also an alternative view developed recently [35][36][37] that a spectral shift cannot occur along a null geodesic. Contrary to the common belief, they notably claim that freely propagating photons, while being transported in an expanding universe, do not change their energy. ...

The Electromagnetic Energy-Momentum Tensor in Expanding Universes
  • Citing Article
  • August 2018

... Such confidence is somehow based on the undoubted success of GR in our immediate spatial environment, with or without a Λ-term which has been termed "dark energy," whose necessity is still debated. There is also an alternative view developed recently [35][36][37] that a spectral shift cannot occur along a null geodesic. Contrary to the common belief, they notably claim that freely propagating photons, while being transported in an expanding universe, do not change their energy. ...

On the Cosmology of Electromagnetic Wave Energy in Expanding Universes
  • Citing Article
  • May 2018

... Such confidence is somehow based on the undoubted success of GR in our immediate spatial environment, with or without a Λ-term which has been termed "dark energy," whose necessity is still debated. There is also an alternative view developed recently [35][36][37] that a spectral shift cannot occur along a null geodesic. Contrary to the common belief, they notably claim that freely propagating photons, while being transported in an expanding universe, do not change their energy. ...

How are Cosmic Photons Redshifted?
  • Citing Article
  • February 2017

... For this reason, the Pedersen conductivity (a scalar conductivity corresponding to the current orthogonal to the magnetic field) can be used to find the thrust-generating component of the current and a full tensor expansion is not required [35]. The electric field generated by the electrodes is shielded through a process known as Debye screening, where the electric charges in the plasma are attracted to regions where oppositely charged fields are applied [49][50][51][52]. This process becomes significant at distance scales of the order of the Debye length. ...

Debye screening under non-equilibrium plasma conditions
  • Citing Article
  • March 2016

Astronomy and Astrophysics

... Such a constant vacuum energy is as yet a physically nonunderstood quantity and is problematic from its physical nature and action. [15][16][17][18][19] There are, however, more recent attempts by Casado 20 and Casado and Jou 21 showing that a "coasting", non-accelerated universe can equally well explain these supernovae luminosities. If in fact vacuum pressure and vacuum energy play a cosmologic role, and if it must be assumed that the universe expands under the thermodynamic and gravodynamic action of vacuum pressure, then as shown by Fahr 22 the unavoidable consequence is a "coasting expansion" of the universe with / ., R dR dt const = = R denoting the scale of the universe. ...

The Thermodynamics of a Gravitating Vacuum
  • Citing Article
  • December 2014

Physical Science International Journal

... This second condition is in fact, and to some surprise for theoreticians, identical with the well known "perfect cosmic dragging" -condition formulated already very early in the last century by Thirring, 18 but for completely different reasons. ...

Cosmic vacuum energy decay and creation of cosmic matter
  • Citing Article
  • October 2007

The Science of Nature