Research

17 pages, 341 KiB

Open AccessFeature PaperArticle

Action Principle for Scale Invariance and Applications (Part I)

by Andre Maeder and Vesselin G. Gueorguiev

Symmetry 2023, 15(11), 1966; https://doi.org/10.3390/sym15111966 - 24 Oct 2023

Cited by 3 | Viewed by 948

On the basis of a general action principle, we revisit the scale invariant field equation using the cotensor relations by Dirac (1973). This action principle also leads to an expression for the scale factor

λ

, which corresponds to the one derived from [...] Read more.

On the basis of a general action principle, we revisit the scale invariant field equation using the cotensor relations by Dirac (1973). This action principle also leads to an expression for the scale factor

λ

, which corresponds to the one derived from the gauging condition, which assumes that a macroscopic empty space is scale-invariant, homogeneous, and isotropic. These results strengthen the basis of the scale-invariant vacuum (SIV) paradigm. From the field and geodesic equations, we derive, in current time units (years, seconds), the Newton-like equation, the equations of the two-body problem, and its secular variations. In a two-body system, orbits very slightly expand, while the orbital velocity keeps constant during expansion. Interestingly enough, Kepler’s third law is a remarkable scale-invariant property. Full article

(This article belongs to the Special Issue Nature and Origin of Dark Matter and Dark Energy)

12 pages, 3899 KiB

Open AccessFeature PaperArticle

Twin Supersymmetric Dark Matter in Light of the First LZ Results

by Marcin Badziak, Giovanni Grilli di Cortona, Keisuke Harigaya and Michał Łukawski

Symmetry 2023, 15(2), 386; https://doi.org/10.3390/sym15020386 - 01 Feb 2023

Cited by 1 | Viewed by 856

Abstract

We review the status of dark matter (DM) candidates in supersymmetric Twin Higgs models in light of the first results of the LUX-ZEPLIN (LZ) experiment. We found that, for twin bino-dominated DM, the new results strengthened the lower bound on the higgsino mass. [...] Read more.

We review the status of dark matter (DM) candidates in supersymmetric Twin Higgs models in light of the first results of the LUX-ZEPLIN (LZ) experiment. We found that, for twin bino-dominated DM, the new results strengthened the lower bound on the higgsino mass. However, a large part of the parameter space consistent with natural electroweak symmetry breaking is still allowed. In the case of twin-stau DM, the new results imply that, if the thermal abundance of the twin-stau LSP fits the observed density of DM, the twin stau cannot have a large left-handed component anymore. Full article

(This article belongs to the Special Issue Nature and Origin of Dark Matter and Dark Energy)

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18 pages, 589 KiB

Open AccessArticle

Weak Deflection Angle, Hawking Radiation and Greybody Bound of Reissner–Nordström Black Hole Corrected by Bounce Parameter

by Wajiha Javed, Mehak Atique, Reggie C. Pantig and Ali Övgün

Symmetry 2023, 15(1), 148; https://doi.org/10.3390/sym15010148 - 04 Jan 2023

Cited by 11 | Viewed by 1491

Abstract

In this study, we probe the weak lensing by a Reissner–Nordström black hole corrected by bounce parameter in plasma and dark matter mediums. For this, the optical geometry and the Gibbons–Werner approach are utilized to obtain the bending angle in the weak field [...] Read more.

In this study, we probe the weak lensing by a Reissner–Nordström black hole corrected by bounce parameter in plasma and dark matter mediums. For this, the optical geometry and the Gibbons–Werner approach are utilized to obtain the bending angle in the weak field limitations. We examine that the impact of these mediums increases the black hole’s bending angle. In addition, we graphically study the deflection angle of light with respect to the impact parameter and examine that the bounce parameter directly affects the angle. Further, we compute the Hawking radiation via a topological method involving two invariants and verify our obtained result with the standard method of calculating the Hawking temperature. In addition, we compute the greybody factor’s bound of the black hole. Moreover, we analyze the bound graphically and observe that the bound shows convergent behavior. We also study that our attained results reduce the results of the Reissner–Nordström and Schwarzschild black holes by reducing the parameters. Finally, we probe how the bounce parameter affected the shadow radius and compared it to the shadow produced if the black hole is immersed in plasma. It is revealed that the rate at which the shadow radius changes with respect to r easily tends to zero under the effect of the bounce parameter, while the plasma merely increases the shadow radius. Full article

(This article belongs to the Special Issue Nature and Origin of Dark Matter and Dark Energy)

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14 pages, 426 KiB

Open AccessFeature PaperArticle

On the Suppression of the Dark Matter-Nucleon Scattering Cross Section in the SE₆SSM

by Roman Nevzorov

Symmetry 2022, 14(10), 2090; https://doi.org/10.3390/sym14102090 - 08 Oct 2022

Cited by 6 | Viewed by 965

Abstract

In the

E_{6}

inspired

U {(1)}_{N}

extension of the minimal supersymmetric (SUSY) standard model (MSSM), a single discrete

{\tilde{Z}}_{2}^{H}

symmetry permits suppressing rapid proton decay and non-diagonal flavor transitions. If matter parity and [...] Read more.

In the

E_{6}

inspired

U {(1)}_{N}

extension of the minimal supersymmetric (SUSY) standard model (MSSM), a single discrete

{\tilde{Z}}_{2}^{H}

symmetry permits suppressing rapid proton decay and non-diagonal flavor transitions. If matter parity and

{\tilde{Z}}_{2}^{H}

symmetry are preserved in this SUSY model (SE

_{6}

SSM), it may involve two dark matter candidates. In this article, we study a new modification of the SE

_{6}

SSM in which the cold dark matter is composed of gravitino and the lightest neutral exotic fermion. We argue that, in this case, the dark matter nucleon scattering cross-section can be considerably smaller than the present experimental limit. Full article

(This article belongs to the Special Issue Nature and Origin of Dark Matter and Dark Energy)

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15 pages, 2375 KiB

Open AccessFeature PaperArticle

The Black Hole Universe, Part II

by Enrique Gaztanaga

Symmetry 2022, 14(10), 1984; https://doi.org/10.3390/sym14101984 - 22 Sep 2022

Cited by 6 | Viewed by 1401

Abstract

In part I of this series, we showed that the observed Universe can be modeled as a local Black Hole of fixed mass

M ≃ 6 \times 10^{22} M_{⊙}

, without Dark Energy: cosmic acceleration is caused by the Black Hole [...] Read more.

In part I of this series, we showed that the observed Universe can be modeled as a local Black Hole of fixed mass

M ≃ 6 \times 10^{22} M_{⊙}

, without Dark Energy: cosmic acceleration is caused by the Black Hole event horizon r_S = 2GM. Here, we propose that such Black Hole Universe (together with smaller primordial Black Holes) could form from the hierarchical free-fall collapse of regular matter. We argue that the singularity could be avoided with a Big Bounce explosion, which results from neutron degeneracy pressure (Pauli exclusion principle). This happens at GeV energies, like in core collapse supernova, well before the collapse reaches Planck energies (10¹⁹ GeV). If our Universe formed this way, there is no need for Cosmic Inflation or a singular start (the Big Bang). Nucleosynthesis and recombination follow a hot expansion, as in the standard model, but cosmological measurements (which are free parameters in the standard model) could in principle be predicted from first principles. Part or all of the Dark Matter could be made up of primordial compact objects (Black Holes and Neutron Stars), remnants of the collapse and bounce. This can provide a faster start for galaxy formation. We present a simple prediction to explain the observed value of

M ≃ 6 \times 10^{22} M_{⊙}

or equivalently

Ω_{Λ}

(the fraction of the critical energy density observed today in form of Dark Energy) and the coincidence problem

Ω_{m} \sim Ω_{Λ}

. Full article

(This article belongs to the Special Issue Nature and Origin of Dark Matter and Dark Energy)

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22 pages, 1447 KiB

Open AccessFeature PaperArticle

The Black Hole Universe, Part I

by Enrique Gaztanaga

Symmetry 2022, 14(9), 1849; https://doi.org/10.3390/sym14091849 - 05 Sep 2022

Cited by 7 | Viewed by 2750

Abstract

The original Friedmann (1922) and Lemaitre (1927) cosmological model corresponds to a classical solution of General Relativity (GR), with the same uniform (FLRW) metric as the standard cosmology, but bounded to a sphere of radius R and empty space outside. We study the [...] Read more.

The original Friedmann (1922) and Lemaitre (1927) cosmological model corresponds to a classical solution of General Relativity (GR), with the same uniform (FLRW) metric as the standard cosmology, but bounded to a sphere of radius R and empty space outside. We study the junction conditions for R to show that a co-moving observer, like us, located anywhere inside R, measures the same background and has the same past light-cone as an observer in an infinite FLRW with the same density. We also estimate the mass M inside R and show that in the observed universe

R < r_{S} \equiv 2

GM, which corresponds to a Black Hole Universe (BHU). We argue that this original Friedmann–Lemaitre model can explain the observed cosmic acceleration without the need of Dark Energy, because

r_{S}

acts like a cosmological constant

Λ = 3 / r_{S}^{2}

. The same solution can describe the interior of a stellar or galactic BHs. In co-moving coordinates the BHU is expanding while in physical or proper coordinates it is asymptotically static. Such frame duality corresponds to a simple Lorentz transformation. The BHU therefore provides a physical BH solution with an asymptotically deSitter metric interior that merges into a Schwarzschild metric exterior without discontinuities. Full article

(This article belongs to the Special Issue Nature and Origin of Dark Matter and Dark Energy)

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17 pages, 707 KiB

Open AccessArticle

An Analytical Approach to the Universal Wave Function and Its Gravitational Effect

by Yunuo Xiong and Hongwei Xiong

Symmetry 2021, 13(2), 193; https://doi.org/10.3390/sym13020193 - 26 Jan 2021

Viewed by 1631

Abstract

Based on quantum origin of the universe, in this article we find that the universal wave function can be far richer than the superposition of many classical worlds studied by Everett. By analyzing the more general universal wave function and its unitary evolutions, [...] Read more.

Based on quantum origin of the universe, in this article we find that the universal wave function can be far richer than the superposition of many classical worlds studied by Everett. By analyzing the more general universal wave function and its unitary evolutions, we find that on small scale we can obtain Newton’s law of universal gravity, while on the scale of galaxies we naturally derive gravitational effects corresponding to dark matter, without modifying any physical principles or hypothesizing the existence of new elementary particles. We find that an auxiliary function having formal symmetry is very useful to predict the evolution of the classical information in the universal wave function. Full article

(This article belongs to the Special Issue Nature and Origin of Dark Matter and Dark Energy)

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24 pages, 854 KiB

Open AccessArticle

Dark Matter as Variations in the Electromagnetic Zero-Point Field Induced by Baryonic Matter

by Yehonatan Knoll

Symmetry 2020, 12(9), 1534; https://doi.org/10.3390/sym12091534 - 17 Sep 2020

Cited by 2 | Viewed by 4186

Abstract

Cold dark-matter, as a solution to the so-called dark-matter problem, suffers from a major internal conflict: In order to dodge direct detection for so long, it must have an unobservably small (non gravitational) interaction with mundane matter, and yet it manages to ‘conspire’ [...] Read more.

Cold dark-matter, as a solution to the so-called dark-matter problem, suffers from a major internal conflict: In order to dodge direct detection for so long, it must have an unobservably small (non gravitational) interaction with mundane matter, and yet it manages to ‘conspire’ with it such that, in single galaxies, its distribution can be inferred from that of mundane matter via the MOND phenomenology. This conflict is avoided if the missing, transparent component of the energy-momentum tensor is due to variations in some electromagnetic ‘zero point field’ (ZPF) which is sourced by mundane matter and contains both its advanced and retarded fields. The existence of a ZPF thus modulated by mundane matter, follows from a proper solution to the self-force problem of classical electrodynamics (CED), recently proposed by the author, which renders CED compatible with the statistical predictions of QM. The possibility that ‘dark matter’ is yet another, hitherto ignored facet of good-old classical electrodynamics, therefore seems no less plausible than it being a highly exotic and conspirative new form of matter. Tests for deciding between the two are proposed. Full article

(This article belongs to the Special Issue Nature and Origin of Dark Matter and Dark Energy)

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7 pages, 300 KiB

Open AccessFeature PaperArticle

Prediction of the Neutrino Mass Scale Using Coma Galaxy Cluster Data

by Peter D. Morley

Symmetry 2020, 12(6), 1049; https://doi.org/10.3390/sym12061049 - 23 Jun 2020

Viewed by 1964

Abstract

The near degeneracy of the neutrino masses—a mass symmetry—allows condensed neutrino objects that may be the Dark Matter everybody is looking for. If the KATRIN terrestrial experiment has a neutrino mass signal, it will contradict the analysis of the Planck Satellite Consortium reduction [...] Read more.

The near degeneracy of the neutrino masses—a mass symmetry—allows condensed neutrino objects that may be the Dark Matter everybody is looking for. If the KATRIN terrestrial experiment has a neutrino mass signal, it will contradict the analysis of the Planck Satellite Consortium reduction of their raw cosmological microwave data. Using Condensed Neutrino Objects as the Dark Matter along with Coma Galaxy Cluster data, we predict that KATRIN will indeed see a neutrino mass signal. If this physics drama unfolds, there will be profound implications for cosmology, which are discussed in this paper. Full article

(This article belongs to the Special Issue Nature and Origin of Dark Matter and Dark Energy)

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Review

Jump to: Research, Other

16 pages, 300 KiB

Open AccessFeature PaperReview

Gravitational Waves, Event Horizons and Black Hole Observation: A New Frontier in Fundamental Physics

by Marco Giammarchi and Fulvio Ricci

Symmetry 2022, 14(11), 2276; https://doi.org/10.3390/sym14112276 - 30 Oct 2022

Viewed by 1611

Abstract

The observation of supermassive black holes by the Event Horizon Telescope Collaboration and the detection of gravitational waves emitted during the merging phase of compact binary objects to stellar-mass black holes by the LIGO–Virgo–KAGRA collaboration constitute major achievements of modern science. Gravitational wave [...] Read more.

The observation of supermassive black holes by the Event Horizon Telescope Collaboration and the detection of gravitational waves emitted during the merging phase of compact binary objects to stellar-mass black holes by the LIGO–Virgo–KAGRA collaboration constitute major achievements of modern science. Gravitational wave signals emitted by stellar-mass black holes are being used to test general relativity in an unprecedented way in the regime of strong gravitational fields, as well as to address other physics questions such as the formation of heavy elements or the Hawking Area Theorem. These discoveries require further research in order to answer critical questions about the population density and the formation processes of binary systems. The detection of supermassive black holes considerably extends the range of scientific investigation by making it possible to probe the structure of spacetime around the horizon of the central mass of our galaxy as well as other galaxies. The huge amount of information collected by the VLBI worldwide network will be used to investigate general relativity in a further range of physical conditions. These investigations hold the potential to pave the way for the detection of quantum-mechanical effects such as a possible graviton mass. In this paper we will review, in a cursory way, some of the results of both the LIGO–Virgo–KAGRA and the EHT collaborations. Full article

(This article belongs to the Special Issue Nature and Origin of Dark Matter and Dark Energy)

Other

Jump to: Research, Review

5 pages, 241 KiB

Open AccessEssay

The Λ and the CDM as Integration Constants

by Priidik Gallagher and Tomi Koivisto

Symmetry 2021, 13(11), 2076; https://doi.org/10.3390/sym13112076 - 03 Nov 2021

Cited by 5 | Viewed by 1270

Abstract

Notoriously, the two main problems of the standard

Λ

CDM model of cosmology are the cosmological constant

Λ

and the cold dark matter, CDM. This essay shows that both the

Λ

and the CDM arise as integration constants in a careful derivation of [...] Read more.

Notoriously, the two main problems of the standard

Λ

CDM model of cosmology are the cosmological constant

Λ

and the cold dark matter, CDM. This essay shows that both the

Λ

and the CDM arise as integration constants in a careful derivation of Einstein’s equations from first principles in a Lorentz gauge theory. The dark sector of the universe might only reflect the geometry of a spontaneous symmetry breaking that is necessary for the existence of spacetime and an observer therein. Full article

(This article belongs to the Special Issue Nature and Origin of Dark Matter and Dark Energy)

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