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Axioms
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String Theory and Mathematical Physics
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String Theory and Mathematical Physics

A special issue of Axioms (ISSN 2075-1680). This special issue belongs to the section "Mathematical Physics".

Deadline for manuscript submissions: closed (30 November 2022) | Viewed by 6689

Special Issue Editors

Prof. Dr. Irina Radinschi

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Guest Editor
Department of Physics, “Gheorghe Asachi” Technical University, 700050 Iasi, Romania
Interests: general relativity and cosmology; computational physics; string theory
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Saibal Ray

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Guest Editor
Centre for Cosmology, Astrophysics and Space Science (CCASS) GLA University, 17th KM Mile Stone, NH-2, Mathura-Delhi Highway Road, P.O. Chaumuhan, Mathura 281406, Uttar Pradesh, India
Interests: general relativity; stellar astrophysics; brane-world model and galactic dynamics; dark energy theory; cosmic expansion
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Farook Rahaman

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Guest Editor
Department of Mathematics, Jadavpur University, Kolkata 700 032, West Bengal, India
Interests: mathematical physics; relativity; cosmology and astrophysics
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Dr. Theophanes Grammenos

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Guest Editor
Department of Civil Engineering, University of Thessaly, 383 34 Volos, Greece
Interests: mathematical physics; general relativity; differential geometry; differential equations
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Dr. Marius-Mihai Cazacu

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Guest Editor
Department of Physics, “Gh. Asachi” Technical University, Iasi 700050, Romania
Interests: physics; optics and spectroscopy; environmental; aerosols
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

"When we understand string theory, we will know how the universe began. It won't have much effect on how we live, but it is important to understand where we come from and what we can expect to find as we explore"—this was a statement by Stephen Hawking and can be regarded as the cornerstone of research in the field of string theory and related subfields. In this context, it is well-known that Albert Einstein, in the later part of his life, attempted to unify the fundamental forces of the physics between elementary particles into a single and grand theoretical framework, which is termed unified field theory and, unfortunately, was unsuccessful.

As background, it is worth noting that the fundamental forces consist of four types: the first two are gravity and electromagnetism, which are macroscopic in nature, and the other two, strong and weak interactions, are very small in scale and occur at the microscopic level. However, based on the current research, the standard model of fundamental interactions provides a unified framework for three of these forces, excluding gravity.

This is, perhaps, one of the key issues posing a challenge regarding the unification problem!  In string theory, a point-like particle is assumed to be composed of tiny oscillating strings, where a particular oscillation of the string can be interpreted as a graviton – the carrier of gravitational energy.

To tie up the tachyon problem, string theorists in the early 1980s introduced supersymmetry in string theory and thus hailed “the first string revolution”. On the other hand, “the second string revolution” started in 1995 when some physicists put forward the idea that the five consistent string theories are actually only different faces of a unique theory that exists in eleven-dimensional spacetime. This is M-theory, which has, to date, played a role as the gateway to the theory of everything (TOE).

String theory is mathematically oriented, and in that sense, M-theory is also based on a mathematically consistent exposition; as such, it is a branch of theoretical physics or mathematical physics. This mathematical aspect of string theory, therefore, forms a bridge between the microcosm and macrocosm.

However, this theory needs to be tested for its viability through several, critical experiments. Today, M-theory is facing rigorous testing at the Large Hadron Collider (LHC) of CERN via the supersymmetry verification scheme. The first evidence for string theory obtained at the LHC, as of 2012 and even in 2014, was not particularly convincing. What, then, is the evidential status of string theory? Either it is just an elaborate hypothesis with many possibilities, or it is, even now, still a toddler trying to walk out with trembling feet.  

Based on the above rationale, through this Special Issue, we would like to invite scientists from various fields to submit their thoughts in the form of research papers on the proposed theme: “String Theory and Mathematical Physics”.

Prof. Dr. Irina Radinschi
Assoc. Prof. Saibal Ray
Prof. Dr. Farook Rahaman
Assist. Prof. Theophanes Grammenos
Dr. Marius-Mihai Cazacu
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Axioms is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Strings and geometry
  • String duality
  • String landscape
  • String theory and quantum gravity
  • Cosmic String
  • String theory and cosmology
  • Superstring theory
  • String field theory
  • String phenomenology
  • Topological string theory
  • M-theory
  • Branes
  • AdS/CFT correspondence

Published Papers (4 papers)

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Research

21 pages, 360 KiB  
Article
On the Radial Solutions of the Dirac Equation in the Kerr-Newman Black Hole Surrounded by a Cloud of Strings
by Saulo S. de Albuquerque Filho, Valdir Barbosa Bezerra and Jefferson Morais Toledo
Axioms 2023, 12(2), 187; https://doi.org/10.3390/axioms12020187 - 10 Feb 2023
Viewed by 993
Abstract
In this paper, we obtain the metric of the space-time generated by a charged and rotating gravitational body surrounded by a loud of strings, namely, the Kerr–Newman black hole space-time with the addition of a cloud of strings. In this background, we find [...] Read more.
In this paper, we obtain the metric of the space-time generated by a charged and rotating gravitational body surrounded by a loud of strings, namely, the Kerr–Newman black hole space-time with the addition of a cloud of strings. In this background, we find the radial solutions of the Dirac equation for massive particles and show that they are given in terms of the Generalized Heun functions. The dependence of these solutions on the parameter that codifies the presence of the cloud of strings is pointed out. Full article
(This article belongs to the Special Issue String Theory and Mathematical Physics)
10 pages, 279 KiB  
Article
The Boundary Homotopy Retract on the Scalar Hairy Charged Black Hole Spacetime
by Mohammed Abu-Saleem and Ali Taani
Axioms 2022, 11(12), 745; https://doi.org/10.3390/axioms11120745 - 19 Dec 2022
Cited by 2 | Viewed by 1045
Abstract
In this paper, we investigate and define the topology of some astrophysical phenomena, like the hairy (scalarized) charged black hole spacetime, to improve our understanding of the kinematics and dynamics of their nature. We use the Lagrangian equation to find different types of [...] Read more.
In this paper, we investigate and define the topology of some astrophysical phenomena, like the hairy (scalarized) charged black hole spacetime, to improve our understanding of the kinematics and dynamics of their nature. We use the Lagrangian equation to find different types of geodesic equations. This can be done under some conditions for the variations of the Cosmological constant and Newton’s constant. We show how to induce the two types (null and spacelike) of geodesics as boundary retractions, in order to obtain the boundary homotopy retract of the scalar charged black hole. These types are used the Lagrangian equation in a 4-D scalar charged black hole to explain the event horizon for this black hole. Full article
(This article belongs to the Special Issue String Theory and Mathematical Physics)
26 pages, 11139 KiB  
Article
A Probe into a (2 + 1)-Dimensional Combined Cosmological Model in f(R, T) Gravity
by Safiqul Islam, Muhammad Aamir, Irina Radinschi and Dwiptendra Bandyopadhyay
Axioms 2022, 11(11), 605; https://doi.org/10.3390/axioms11110605 - 01 Nov 2022
Viewed by 1199
Abstract
This research is an extension of our earlier published (2+1) dimensional cosmological models in f(R,T) gravity with Λ(R,T) (IOP Conf. Ser. J. Phys. Conf. Ser. 2019, 1258 [...] Read more.
This research is an extension of our earlier published (2+1) dimensional cosmological models in f(R,T) gravity with Λ(R,T) (IOP Conf. Ser. J. Phys. Conf. Ser. 2019, 1258, 012026). A different class of cosmological space model is studied under modified theories of f(R,T) gravity, where the cosmological constant Λ is expressed as a function of the Ricci scalar R and the trace of the stress-energy momentum tensor T. We call such a model as “Λ(R,T) gravity”. Such a specific form of Λ(R,T) has been defined in the dust as well as in the perfect fluid case. We intend to search for a combined model that satisfies the equation of state for dark energy matter or quintessence matter or perfect matter fluid. Some geometric and intrinsic physical properties of the model are also described. The energy conditions, pressure and density are discussed both when Λ=Λ(r) is a function of the radial parameter r, as well as when Λ is zero. We study the effective mass function and also the gravitational redshift function, both of which are found to be positive as per the latest observations. The cosmological model is studied in f(R,T) modified theory of gravity, where the gravitational Lagrangian is expressed both in terms of the Ricci scalar R and the trace of the stress-energy tensor T. The equation of state parameter is discussed in terms of ω corresponding to the three cases mentioned above. The behaviour of the cosmological constant is separately examined in the presence of quintessence matter, dark energy matter and perfect fluid matter. Full article
(This article belongs to the Special Issue String Theory and Mathematical Physics)
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10 pages, 289 KiB  
Article
Covariant Space-Time Line Elements in the Friedmann–Lemaitre–Robertson–Walker Geometry
by David Escors and Grazyna Kochan
Axioms 2022, 11(7), 310; https://doi.org/10.3390/axioms11070310 - 26 Jun 2022
Cited by 1 | Viewed by 1548
Abstract
Most quantum gravity theories quantize space-time on the order of Planck length (ℓp ). Some of these theories, such as loop quantum gravity (LQG), predict that this discreetness could be manifested through Lorentz invariance violations (LIV) over travelling particles at [...] Read more.
Most quantum gravity theories quantize space-time on the order of Planck length (ℓp ). Some of these theories, such as loop quantum gravity (LQG), predict that this discreetness could be manifested through Lorentz invariance violations (LIV) over travelling particles at astronomical length distances. However, reports on LIV are controversial, and space discreetness could still be compatible with Lorentz invariance. Here, it is tested whether space quantization on the order of Planck length could still be compatible with Lorentz invariance through the application of a covariant geometric uncertainty principle (GeUP) as a constraint over geodesics in FRW geometries. Space-time line elements compatible with the uncertainty principle are calculated for a homogeneous, isotropic expanding Universe represented by the Friedmann–Lemaitre–Robertson–Walker solution to General Relativity (FLRW or FRW metric). A generic expression for the quadratic proper space-time line element is derived, proportional to Planck length-squared, and dependent on two contributions. The first is associated to the energy–time uncertainty, and the second depends on the Hubble function. The results are in agreement with space-time quantization on the expected length orders, according to quantum gravity theories, and within experimental constraints on putative LIV. Full article
(This article belongs to the Special Issue String Theory and Mathematical Physics)
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