Big Bang nucleosynthes describes a significant process in the early universe, responsible for the formation of light nuclei a while after the Big Bang explosion. Its sensitivity to the expansion rate makes BBN an effective probe for testing deviations from standard cosmology, particularly within the framework of modified theories of gravity. In this article, we investigate the evolution of the Universe through Big Bang nucleosynthesis within the framework of <math altimg='si2.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>T</mi><mo>,</mo><mspace width='0.25em' /><mi>B</mi><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>T</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>B</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo stretchy='false'>)</mo></math> gravity. Here, <math altimg='si3.svg'><mi>T</mi><mo>,</mo><mspace width='0.25em' /><mi>B</mi><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>T</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub></math> and <math altimg='si4.svg'><msub><mrow><mi>B</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub></math> correspond to the torsion, boundary term, teleparallel Gauss-Bonnet term, and Gauss-Bonnet boundary term, respectively. To explore the deviation from the teleparallel equivalent of general relativity, we apply the transformation <math altimg='si2.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>T</mi><mo>,</mo><mspace width='0.25em' /><mi>B</mi><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>T</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>B</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo stretchy='false'>)</mo></math> = <math altimg='si5.svg'><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mi>T</mi><mo linebreak='goodbreak' linebreakstyle='after'>+</mo><mi mathvariant='script'>F</mi><mo stretchy='false'>(</mo><mi>T</mi><mo>,</mo><mspace width='0.25em' /><mi>B</mi><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>T</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>B</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo stretchy='false'>)</mo></math>. For an in-depth analysis of the Big Bang nucleosynthesis, we choose five distinct models from gravity and compared the results with the observational limits on <math altimg='si6.svg'><mo stretchy='true'>|</mo><mfrac><mrow><mi mathvariant='normal'>&#916;</mi><msub><mrow><mi mathvariant='script'>T</mi></mrow><mrow><mi>f</mi></mrow></msub></mrow><mrow><msub><mrow><mi mathvariant='script'>T</mi></mrow><mrow><mi>f</mi></mrow></msub></mrow></mfrac><mo stretchy='true'>|</mo></math> to examine restrictions on the free parameters associated with these models. Our outcomes indicate that <math altimg='si2.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>T</mi><mo>,</mo><mspace width='0.25em' /><mi>B</mi><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>T</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo>,</mo><mspace width='0.25em' /><msub><mrow><mi>B</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo stretchy='false'>)</mo></math> gravity can agree with the constraint of big bang nucleosynthesis, and hence build a valid view of the universe. Moreover, we take the limiting cases of the assumed theory, that is, <math altimg='si7.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>T</mi><mo>,</mo><mi>B</mi><mo stretchy='false'>)</mo></math> and <math altimg='si8.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>T</mi><mo stretchy='false'>)</mo></math> theories, which also ensure consistency with BBN data.

Pakistan

Abdul Malik Sultan

Manahil Ali

China

Shamaila Rani

Azerbaijan

Nadeem Azhar

Kazakhstan

N. Myrzakulov

Uzbekistan

Sanjar Shaymatov

Constraining Big Bang nucleosynthesis in <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>T</mi><mo>,</mo><mi>B</mi><mo>,</mo><msub><mrow><mi>T</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo>,</mo><msub><mrow><mi>B</mi></mrow><mrow><mi mathvariant='script'>G</mi></mrow></msub><mo stretchy='false'>)</mo></math> gravity

We analyze the effect of a variation of the strange nucleon matrix element $$ \left\langle N|{m}_s\overline{s}s|N\right\rangle $$ on the abundances of the light elements produced in the Big Bang. For that, we vary the nucleon mass in the leading eight reactions that involve neutrons, protons and the four lightest nuclei. We use various available Big Bang nucleosynthesis codes and find that the measured deuterium and He abundances set strict limits on the nucleon mass variations. This translates into an upper bound of possible variations of the strange quark mass, |∆$\textit{m}$ /$\textit{m}$ | ≤ 5.1%.

Germany

Ulf-G. Meißner

Bernard Metsch

Helen Meyer

Bounds on variations of the strange quark mass from Big Bang nucleosynthesis

We present an expanding, spatially flat ( <math altimg='si1.svg'><mi>k</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>0</mn></math>) FLRW quantum spacetime with a Big Bang, considered as a background in Yang-Mills matrix models. The FLRW geometry emerges in the semi-classical limit as a projection from the fuzzy hyperboloid. We analyze the propagation of scalar fields, and demonstrate that their Feynman propagator resembles the Minkowski space Feynman propagator in the semi-classical regime. Moreover, the higher spin modes predicted by the matrix model are described explicitly. These results are compared to recent results on <math altimg='si2.svg'><mi>k</mi><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>1</mn></math> FLRW quantum spacetimes with a Big Bounce.

Austria

Christian Gaß

Harold C. Steinacker

Spatially flat FLRW spacetimes with a Big Bang from matrix geometry

We study the transverse momentum ( $p_T$ ) differential anisotropic flow and flow fluctuation in Pb+Pb collisions at $\sqrt{s_{_{NN}}}$ =5.02 TeV at the LHC. A (3+1)-dimensional CLVisc hydrodynamics framework with fluctuating TRENTO (or AMPT) initial conditions is utilized to simulate the space-time evolution of the quark-gluon plasma (QGP) medium. The effects of shear viscosity and the sub-nucleon structure on anisotropic flow and flow fluctuation are analyzed. Our result shows that shear viscosity tends to suppress both flow coefficients ( ${v_2\{2}\}$ , ${v_2\{4\}}$ , and ${\langle v_2\rangle}$ ) and flow fluctuation ( ${\sigma_{v_2}}$ ) owing to its smearing effect on local density fluctuation. The flow coefficients appear to be insensitive to the sub-nucleon structure, whereas the flow fluctuation ${\sigma_{v_2}}$ tends to be suppressed by the sub-nucleon structure in central collisions but enhanced in peripheral collisions. After taking into account the sub-nucleon structure effect, our numerical result can qualitatively describe the relative flow fluctuations ( ${v_2\{4\}/v_2\{2\}}$ , $F({v_2})$ ) measured by the ALICE Collaboration at the LHC. We further investigate the effects of shear viscosity, sub-nucleon structure, and initial condition model on the flow angle and flow magnitude decorrelations ( ${A_2^f}$ , ${M_2^f}$ ) using the four-particle correlation method. We find that the flow decorrelation effect is typically stronger in central collisions than in peripheral collisions. The flow angle decorrelation is found to be insensitive to the shear viscosity and sub-nucleon structure, whereas the flow magnitude decorrelation shows quite different behaviors when using the TRENTO and AMPT initial condition models. Our study sheds light on the anisotropic flow, transport properties, and initial structure of the QGP created in high-energy nuclear collisions.

Jie Zhu

Canada

Xiang-Yu Wu

Guang-You Qin

Anisotropic flow, flow fluctuation, and flow decorrelation in relativistic heavy-ion collisions: the roles of sub-nucleon structure and shear viscosity * Supported in part by the Natural Science Foundation of China (12225503, 11890710, 11890711, 11935007). Zhu Jie is supported in part by the China Scholarship Council (202306770009). Wu Xiang-Yu is supported in part by the National Science Foundation within the framework of the JETSCAPE collaboration (OAC-2004571) and in part by the Natural Sciences and Engineering Research Council of Canada. Some of the calculations were performed in the Nuclear Science Computing Center at Central China Normal University (NSC$^{3}$), Wuhan, Hubei, China.

We continue the study of dipole cosmology framework put forward in Krishnan et al. (JCAP 07:020, 2023), a beyond FLRW setting that has a preferred direction in the metric which may be associated with a cosmological tilt, a cosmic dipole. In this setup the shear and the tilt can be positive or negative given the dipole direction. We thoroughly analyze evolution of the universe in this setting, particularly focusing on the behaviour near the Big Bang (BB). We first analyze a single fluid model with a generic constant equation of state . While details of the behavior near the BB depends on and the other initial conditions, we find that when the shear is negative we have a shear dominated BB singularity, whereas for a positive shear we have a much milder singularity, the whimper singularity (Ellis and King in Commun Math Phys 38:119–156, 1974), at which the tilt blows up while curvature invariants remain finite. We then consider dipole $$\Lambda $$ CDM model which besides the shear has two tilt parameters, one for radiation and one for the pressureless matter. For positive (negative) shear we again find whimper (curvature) singularity near the BB. Moreover, when the tilt parameters have opposite signs, the shear can change sign from negative to positive in the course of evolution of the Universe. We show that the relative tilt of the radiation and the matter generically remains sizable at late times.

Iran

A. Allahyari

Italy

E. Ebrahimian

India

R. Mondol

M. Sheikh-Jabbari

Big Bang in dipole cosmology

Erratum to: Improved constraints on the variation of the weak scale from Big Bang nucleosynthesis

All of the significant evidence for dark matter observed thus far has been through its gravitational interactions. After 40 years of direct detection experiments, the parameter space for weakly interacting massive particles (WIMPs) as dark matter candidates is rapidly approaching the neutrino floor. Moreover, there have been no signs of WIMPs in any particle production experiments so far. In this light, we consider a dark sector that is strongly decoupled from the visible sector, interacting exclusively through gravity. In this model, proposed by Freese and Winkler [Dark matter and gravitational waves from a dark big bang, Phys. Rev. D 107, 083522 (2023)], dark matter can be produced through a first-order phase transition in the dark sector dubbed “the dark big bang.” We fully determine the allowed region of parameter space for the tunneling potential that leads to the realization of a dark big bang and is consistent with all experimental bounds available.

United States

Richard Casey

Cosmin Ilie

Dark sector tunneling field potentials for a dark big bang

We propose a mechanism of preheating stage after inflation, using a new idea of parametrically amplified super-radiance. Highly coherent state, characterized by macro-coherence of scalar field coupled to produced massless particle in pairs, is created by parametric resonance effects associated with field oscillation around its potential minimum, within a Hubble volume. The state is described effectively by the simple Dicke-type of super-radiance model, and super-radiant pulse is emitted within a Hubble time, justifying neglect of cosmic expansion. Produced particles are shown to interact to change their energy and momentum distribution to realize thermal hot big bang universe. A long standing problem of heating after inflation may thus be solved. A new dark matter candidate produced at the emergence of thermalized universe is suggested as well.

Japan

Motohiko Yoshimura

Kunio Kaneta

Kin-ya Oda

Parametrically amplified super-radiance towards hot big bang universe

We study the impact of an early dark energy component (EDE) present during big bang nucleosynthesis (BBN) on the elemental abundances of deuterium D/H, and helium <math><msub><mi>Y</mi><mi>p</mi></msub></math>, as well as the effective relativistic degrees of freedom <math><msub><mi>N</mi><mi>eff</mi></msub></math>. We consider a simple model of EDE that is constant up to a critical time. After this critical time, the EDE transitions into either a radiation component that interacts with the electromagnetic plasma, a dark radiation component that is uncoupled from the plasma, or kination that is also uncoupled. We use measured values of the abundances and <math><msub><mi>N</mi><mi>eff</mi></msub></math> as determined by cosmic microwave background observations to establish limits on the input parameters of this EDE model. In addition, we explore how those parameters are correlated with BBN inputs; the baryon to photon ratio <math><msub><mi>η</mi><mi>b</mi></msub></math>, neutron lifetime <math><msub><mi>τ</mi><mi>n</mi></msub></math>, and number of neutrinos <math><msub><mi>N</mi><mi>ν</mi></msub></math>. Finally, we study whether this setup can alleviate the tension introduced by recent measurements of the primordial helium abundance.

David McKeen

Afif Omar

Early dark energy during big bang nucleosynthesis

In models featuring extra spatial dimensions, particle collisions in the early Universe can produce Kaluza-Klein gravitons. Such particles will later decay, potentially impacting the process of big bang nucleosynthesis. In this paper, we consider scenarios in which gravity is free to propagate throughout <math><mi>n</mi></math> flat, compactified extra dimensions, while the fields of the Standard Model are confined to a (<math><mrow><mn>3</mn><mo>+</mo><mn>1</mn></mrow></math>)-dimensional brane. We calculate the production and decay rates of the states that make up the Kaluza-Klein graviton tower and determine the evolution of their abundances in the early Universe. We then go on to evaluate the impact of these decays on the resulting light element abundances. We identify significant regions of previously unexplored parameter space that are inconsistent with measurements of the primordial helium and deuterium abundances. In particular, we find that for the case of one extra dimension (two extra dimensions), the fundamental scale of gravity must be <math><mrow><msub><mrow><mi>M</mi></mrow><mrow><mo>⋆</mo></mrow></msub><mo>≳</mo><mn>2</mn><mo>×</mo><msup><mrow><mn>10</mn></mrow><mrow><mn>13</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math> (<math><mrow><msub><mrow><mi>M</mi></mrow><mrow><mo>⋆</mo></mrow></msub><mo>≳</mo><mn>1</mn><msup><mrow><mn>0</mn></mrow><mrow><mn>10</mn></mrow></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></mrow></math>) unless the temperature of the early Universe was never greater than <math><mi>T</mi><mo>∼</mo><mn>2</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math> (<math><mi>T</mi><mo>∼</mo><mn>1</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>). For larger values of <math><mi>n</mi></math>, these constraints are less stringent. For the case of <math><mi>n</mi><mo>=</mo><mn>6</mn></math>, for example, our analysis excludes all values of <math><msub><mi>M</mi><mo>⋆</mo></msub></math> less than <math><mo>∼</mo><msup><mn>10</mn><mn>6</mn></msup><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, unless the temperature of the Universe was never greater than <math><mi>T</mi><mo>∼</mo><mn>3</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>. The results presented here severely limit the possibility that black holes were efficiently produced through particle collisions in the early Universe’s thermal bath.

France

Mathieu Gross

Dan Hooper

Kaluza-Klein graviton freeze-in and big bang nucleosynthesis