We present a unified treatment of cosmic inflation within the framework of Myrzakulov Gravity, exploring its realization in three different formalisms: metric (curvature-based), teleparallel (torsion-based), and symmetric teleparallel (non-metricity-based). For each case, we derive the corresponding field equations in a flat FLRW background, study inflationary solutions driven by a scalar field, and compute observable quantities such as the scalar spectral index <math altimg='si1.svg'><msub><mrow><mi>n</mi></mrow><mrow><mi>s</mi></mrow></msub></math> and the tensor-to-scalar ratio <italic>r</italic>.

South Africa

United States

Davood Momeni

Kazakhstan

Ratbay Myrzakulov

Inflation in Myrzakulov <italic>F</italic>( <italic>R</italic>, <italic>T</italic>) gravity: A comparative study in metric, symmetric teleparallel, and Weitzenb&#246;ck formalisms

Inspired by recent developments in the study of the model of double scaled SYK (DSSYK), as elucidated in a recent paper, we embark on a re-evaluation of the Sachdev-Ye-Kitaev (SYK) model. Our motivation stems from the insights gained from the DSSYK model, particularly its ability to capture essential features of quantum dynamics and gravitational effects. In this work, we delve into the SYK model, uncovering precise solutions for the two-point function and self-energy that have not been previously reported. Building upon the advancements made in particle physics phenomenology, we extend the SYK model to encompass tensor field theory. Through the incorporation of a cutoff term to ensure convergence, we substantially advance our understanding of quantum many-body physics. Our investigation extends to experimental parameter estimation and the exploration of cutoff dependency in random couplings, providing invaluable insights into system dynamics. The introduction of a novel tensor field theory replaces conventional fermionic degrees of freedom with tensorial counterparts, leading to the discovery of intriguing phase transition phenomena characterized by a first-order transition. Furthermore, we elucidate a direct linear relationship between the coupling parameter and the cutoff scale. These findings not only shed light on emergent behavior across both high-energy physics and condensed matter systems but also pave the way for further theoretical and experimental exploration, inspired by the recent advancements in the SYK model.

Unveiling novel insights in quantum dynamics through extended Sachdev-Ye-Kitaev model

The study of modified gravity models has garnered significant attention because of their potential to provide alternative explanations for cosmological phenomena, such as the accelerated expansion of the universe and the nature of dark energy. One such model, the Einstein–Gauss–Bonnet–Myrzakulov <math altimg='si1.svg'><mi>R</mi><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><mi>F</mi><mo stretchy='false'>(</mo><mi>T</mi><mo>,</mo><mi>G</mi><mo stretchy='false'>)</mo></math> gravity (EGBMG), which incorporates the curvature <italic>R</italic>, torsion <italic>T</italic>, and the Gauss-Bonnet term <italic>G</italic>, offers a promising framework to explore the dynamics of the universe and its evolution. This paper delves into the theoretical and observational implications of the EGBMG model, focusing on its ability to address long-standing challenges in cosmology, including the evolution of dark energy and the transition from early-time inflationary behavior to late-time acceleration. We review recent advancements in the model, including its compatibility with observational data and its ability to provide new insights into cosmic acceleration. Through a combination of theoretical models, dynamical systems analysis, and cosmological diagnostics, we demonstrate the robustness of the EGBMG framework in explaining the large-scale structure of the universe and its accelerated expansion. This paper serves as a step toward further exploring the potential of this model to understand the fundamental forces driving the cosmos and its consistency with modern observational constraints in Weitzenb&#246;ck spacetime.

Einstein–Gauss–Bonnet–Myrzakulov gravity from <italic>R</italic>&#8239;+&#8239; <italic>F</italic>( <italic>T</italic>, <italic>G</italic>): Numerical insights and torsion&#8211;Gauss&#8211;Bonnet dynamics in Weitzenb&#246;ck spacetime

The quest to understand the nature of gravity and its role in shaping the universe has led to the exploration of modified gravity theories. One of the pioneering contributions in this field is the Myrzakulov gravity theory, which incorporates both curvature and torsion. In this work, we investigate the effects of torsion within the framework of <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo stretchy='false'>)</mo></math>-gravity, a modification of General Relativity that incorporates both curvature and torsion.

Myrzakulov gravity in vielbein formalism: A study in Weitzenböck spacetime

We explore the shadows and photon orbits of both static and rotating traversable wormholes by employing a redshift function in combination with two distinct shape functions. Using the null geodesic equation derived from the Euler-Lagrange formalism, we investigate the gravitational lensing effects and the motion of photons in strong gravitational fields. Our study presents numerical simulations of ray tracing and intensity profiles to examine the observational signatures of traversable wormholes. The results reveal that the shadows of rotating wormholes exhibit asymmetry due to frame-dragging effects, akin to those seen in Kerr black holes. Furthermore, we compare the properties of wormhole shadows and photon spheres to those of black holes, highlighting key differences that may serve as potential observational signatures. These findings provide insights into the feasibility of detecting traversable wormholes through high-resolution astrophysical observations and gravitational lensing studies.

Thailand

Takol Tangphati

Phongpichit Channuie

Japan

Kazuharu Bamba

Shadows and photon spheres in static and rotating traversable wormholes

In this study, we explore the dynamics of warm inflation within a non-minimally coupled Peccei–Quinn (PQ) framework and evaluate its compatibility with the de Sitter Swampland Conjecture. Our model incorporates a PQ scalar field that is non-minimally coupled to gravity, facilitating inflation through a dissipative process that sustains a thermal bath, thereby distinguishing it from conventional cold inflation. We analyze the dissipation coefficient defined as <math altimg='si1.svg'><mi mathvariant='normal'>&#915;</mi><mo stretchy='false'>(</mo><mi>T</mi><mo>,</mo><mi>&#963;</mi><mo stretchy='false'>)</mo><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><msub><mrow><mi>C</mi></mrow><mrow><mi>n</mi></mrow></msub><msup><mrow><mi>T</mi></mrow><mrow><mi>n</mi></mrow></msup><msup><mrow><mi>&#963;</mi></mrow><mrow><mi>p</mi></mrow></msup><msup><mrow><mi>M</mi></mrow><mrow><mn>1</mn><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mi>n</mi><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mi>p</mi></mrow></msup></math>, where <math altimg='si2.svg'><msub><mrow><mi>C</mi></mrow><mrow><mi>n</mi></mrow></msub></math> is a dimensionless constant, <italic>M</italic> is a mass scale, and <italic>n</italic> and <italic>p</italic> are numerical powers. Our investigation focuses on three specific cases: (a) A temperature-dependent dissipation coefficient with an inverse relation, <math altimg='si3.svg'><mi mathvariant='normal'>&#915;</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><msub><mrow><mi>C</mi></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>1</mn></mrow></msub><mspace width='0.2em' /><msup><mrow><mi>&#963;</mi></mrow><mrow><mn>2</mn></mrow></msup><mo stretchy='false'>/</mo><mi>T</mi></math>, where <math altimg='si4.svg'><mi>n</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>1</mn></math> and <math altimg='si5.svg'><mi>p</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>2</mn></math>; (b) A dissipation coefficient linear in field <italic>&#981;</italic>, <math altimg='si6.svg'><mi mathvariant='normal'>&#915;</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><msub><mrow><mi>C</mi></mrow><mrow><mn>0</mn></mrow></msub><mi>&#963;</mi></math>, where <math altimg='si7.svg'><mi>n</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>0</mn></math> and <math altimg='si8.svg'><mi>p</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>1</mn></math>; and (c) A dissipation coefficient linear in temperature <italic>T</italic>, <math altimg='si9.svg'><mi mathvariant='normal'>&#915;</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><msub><mrow><mi>C</mi></mrow><mrow><mn>1</mn></mrow></msub><mi>T</mi></math>, where <math altimg='si10.svg'><mi>n</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>1</mn></math> and <math altimg='si11.svg'><mi>p</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>0</mn></math>. By examining the slow-roll dynamics in these inflationary scenarios, we derive essential cosmological parameters, including the scalar spectral index and the tensor-to-scalar ratio. We compare our results with the latest observational data from Planck 2018. Our findings suggest that the model is consistent with observational constraints while simultaneously satisfying the de Sitter Swampland conditions.

Jureeporn Yuennan

Warm non-minimally coupled Peccei–Quinn inflation and de Sitter Swampland conjecture

In this work, we study several extensions of the higher curvature modification of  $$R^{2}$$  <math> <msup> <mi>R</mi> <mn>2</mn> </msup> </math>   inflation in the context of gravity’s rainbow. We modify the  $$(R+R^{2})$$  <math> <mrow> <mo>(</mo> <mi>R</mi> <mo>+</mo> <msup> <mi>R</mi> <mn>2</mn> </msup> <mo>)</mo> </mrow> </math>   model by adding an  $$f_{1}R^3$$  <math> <mrow> <msub> <mi>f</mi> <mn>1</mn> </msub> <msup> <mi>R</mi> <mn>3</mn> </msup> </mrow> </math>  -term, an  $$f_{2}R^4$$  <math> <mrow> <msub> <mi>f</mi> <mn>2</mn> </msub> <msup> <mi>R</mi> <mn>4</mn> </msup> </mrow> </math>  -term, and an  $$f_{3}R^{3/2}$$  <math> <mrow> <msub> <mi>f</mi> <mn>3</mn> </msub> <msup> <mi>R</mi> <mrow> <mn>3</mn> <mo>/</mo> <mn>2</mn> </mrow> </msup> </mrow> </math>  -term to the original model. We calculate the inflationary observables and confront them using the latest observational bounds from Planck 2018 data. We assume the rainbow function of the form  $${\tilde{f}}=1+\left( \frac{H}{M}\right) ^{\lambda }$$  <math> <mrow> <mover> <mi>f</mi> <mo>~</mo> </mover> <mo>=</mo> <mn>1</mn> <mo>+</mo> <msup> <mfenced> <mfrac> <mi>H</mi> <mi>M</mi> </mfrac> </mfenced> <mi>λ</mi> </msup> </mrow> </math>   with  $$\lambda $$  <math> <mi>λ</mi> </math>   being a rainbow parameter and M a mass-dimensional parameter. We demonstrate that the power spectrum of curvature perturbation relies on the dimensionless coefficient  $$f_{i},\,i=1,2,3$$  <math> <mrow> <msub> <mi>f</mi> <mi>i</mi> </msub> <mo>,</mo> <mspace width="0.166667em"></mspace> <mi>i</mi> <mo>=</mo> <mn>1</mn> <mo>,</mo> <mn>2</mn> <mo>,</mo> <mn>3</mn> </mrow> </math>  , a rainbow parameter  $$\lambda $$  <math> <mi>λ</mi> </math>   and a ratio H/M. Likewise, the scalar spectral index  $$n_s$$  <math> <msub> <mi>n</mi> <mi>s</mi> </msub> </math>   is affected by both  $$f_{i}$$  <math> <msub> <mi>f</mi> <mi>i</mi> </msub> </math>   and the rainbow parameter. Moreover, the tensor-to-scalar ratio r is solely determined by the rainbow parameter. Interestingly, by ensuring that  $$n_s$$  <math> <msub> <mi>n</mi> <mi>s</mi> </msub> </math>   aligns with the Planck collaboration’s findings at the  $$1\sigma $$  <math> <mrow> <mn>1</mn> <mi>σ</mi> </mrow> </math>   confidence level, the tensor-to-scalar ratio could reach up to  $$r\sim 0.01$$  <math> <mrow> <mi>r</mi> <mo>∼</mo> <mn>0.01</mn> </mrow> </math>  , which is possibly measurable for detection in forthcoming Stage IV CMB ground experiments and is certainly feasible for future dedicated space missions.

Gravity’s rainbow effects on higher curvature modification of  $$R^{2}$$  <math> <msup> <mi>R</mi> <mn>2</mn> </msup> </math>   inflation

We investigate static cylindrical solutions within an extended theory of modified gravity. By incorporating various coupling functions through a straightforward boost symmetry approach, we establish the equations of motion in a self-consistent manner and subsequently determine the linear scalar field profile. Utilizing analytical methods, we solve the system of equations for the metric functions and the <math><mi>U</mi><mo>(</mo><mn>1</mn><mo>)</mo></math> gauge field, revealing their dependence on Bessel's functions. To comprehend gravito-objects exhibiting cylindrical symmetry, we develop a perturbative framework aimed at identifying all nontrivial solutions for the scalar profiles. Introducing first-order truncated perturbation equations for the gauge field, synchronized with metric gauges and electromagnetic field considerations, we demonstrate their integrability and obtain solutions through quadrature. Our findings suggest the feasibility of obtaining self-gravitating cylindrical structures within the scalar-vector-tensor theory. These cylindrical structures could provide insights into the behavior of gravitational and gauge fields in modified gravity, potentially offering new perspectives on astrophysical phenomena such as cosmic strings and cylindrical gravitational waves.

Oman

Mudhahir Al-Ajmi

Exploring self-gravitating cylindrical structures in modified gravity: Insights from scalar-vector-tensor theory

In this work, we study the rotating wormhole geometries supported by a three-form field. We demonstrate for particular choices of parameters that it is possible for the matter fields threading the wormhole to satisfy the null and weak energy conditions throughout the spacetime, when the three-form field is present. In this case, the form field is interpreted as supporting the wormhole and the energy condition violation is restricted only to the 3-form fields. Thus, the three-form curvature terms, which may be interpreted as a gravitational fluid, sustain these wormhole geometries. Additionally, we also address the ergoregion of the solutions.

Butsayapat Chaihao

Daris Samart

Rotating traversable wormhole geometries in the presence of three-form fields

In this work, we study the non-minimally-coupled Higgs model in the context of warm inflation scenario on both metric and Palatini approaches. We particularly consider a dissipation parameter of the form <math><mi>Γ</mi><mo>=</mo><msub><mrow><mi>C</mi></mrow><mrow><mi>T</mi></mrow></msub><mi>T</mi></math> with <math><msub><mrow><mi>C</mi></mrow><mrow><mi>T</mi></mrow></msub></math> being a coupling parameter and focus only on the strong regime of the interaction between inflaton and radiation fluid. We compute all relevant cosmological parameters and constrain the models using the observational Planck 2018 data. We discover that the <math><msub><mrow><mi>n</mi></mrow><mrow><mi>s</mi></mrow></msub></math> and r values are consistent with the observational bounds. Having used the observational data, we constrain a relation between ξ and λ for the non-minimally-coupled warm Higgs inflation in both metric and Palatini cases. To produce <math><msub><mrow><mi>n</mi></mrow><mrow><mi>s</mi></mrow></msub></math> and r in agreement with observation, we find that their values are two orders of magnitude higher than those of the usual (cold) non-minimally-coupled Higgs inflation.