arXiv subjects

Cheng Tao Yang

Publications and source records attributed to Cheng Tao Yang.

17 recordsLinked to original sources

arXiv2026

Weinberg Angle, Neutron Abundance in BBN, and Lifetime

We present state of the art kinetic theory determination of the neutron abundance available for the Big-Bang nucleosynthesis (BBN). Our work is motivated by the study of the neutron lifespan measured in the laboratory and the unknown strength of weak interactions coupling constant $G_\mathrm{F}$ at finite temperature in the primordial Universe. We draw attention to the relevant dependence of $G_\mathrm{F}$ on the symmetry breaking Weinberg angle $s^2_\mathrm{W}$, a free parameter in the standard model of particle physics. We establish how the value of $s^2_\mathrm{W}$ by way of $G_\mathrm{F}$ modification influences neutron abundance available for BBN and neutron lifetime.

hep-ph↗

arXiv2025

Higgs Thermal Nonequilibrium in Primordial QGP

In this work we investigate the chemical and kinetic nonequilibrium dynamics of the Higgs boson during the primordial Universe QGP (quark-gluon plasma) epoch $130\mathrm{\,GeV}>T>10\mathrm{\,GeV}$. We show that the Higgs bosons is always out of chemical abundance equilibrium with a fugacity $Υ_h = 0.69$ due to virtual decay channels. Additionally, Higgs momentum distribution is found to be ``cold'' for $T<25$\,GeV, since the scattering rate drops below the production rate.

hep-ph↗

arXiv2025

Higgs in The Cosmos

We explore the Higgs particle in the cosmic quark-gluon plasma (QGP) below the electroweak phase transition temperature $T_\mathrm{EW}\simeq 125\mathrm{\,GeV}$. We show that Higgs is neither in abundance (chemical) nor in momentum distribution equilibrium in certain stages of the Universe evolution. Nonequilibrium originates in: For chemical nonequilibrium in the always present irreversible decays into virtual heavy gauge bosons, and; For $T<25$\,GeV in relatively rapid $2\leftrightarrow 1$ formation and decay processes yielding momentum distribution as created in these reactions. As heavy particles disappear, the minimal Higgs coupling to abundant low mass particles fails in $2\to2$ (two-particle) scattering processes to assure a kinetic distribution equilibrium. The expansion of the Universe is by more than 10 orders of magnitude slower compared to microscopic processes. All other particles in the Universe are in full thermal equilibrium, with exception of the late in QGP evolution of the bottom flavor near to hadronization condition.

hep-ph↗

arXiv2025

Quarks to Cosmos: Particles and Plasma in Cosmological evolution

We describe in the context of the particle physics (PP) standard model (SM) `PP-SM' the understanding of the primordial properties and composition of the Universe in the temperature range $130\GeV>T>20\keV$. The Universe evolution is described using FLRW cosmology. We present a global view on particle content across time and describe the different evolution eras using deceleration parameter $q$. We follow the arrow of time in the expanding and cooling Universe: After the PP-SM heavies $(t, h, W, Z)$ diminish in abundance below $T\simeq 50\GeV$, the PP-SM plasma in the Universe is governed by the strongly interacting Quark-Gluon content. Once the temperature drops below $T\simeq 150\MeV$, quarks and gluons hadronize into strongly interacting matter particles. Rapid disappearance of baryonic antimatter completes at $T_\mathrm{B}=38.2\MeV$. We study the ensuing disappearance of strangeness and mesons in general. We show that the different eras defined by particle populations are barely separated from each other with abundance of muons fading out just prior to $T=\mathcal{O}(2.5)\MeV$, the era of emergence of the free-streaming neutrinos. We discuss the two relevant fundamental constants controlling the decoupling of neutrinos. We subsequently follow the primordial Universe as it passes through the hot dense electron-positron plasma epoch. The high density of positron antimatter disappears near $T=20.3\keV$: Nuclear reactions occur in the presence of a highly mobile and relatively strongly interacting electron-positron plasma phase. We apply plasma theory methods to describe the strong screening effects between heavy dust particle (nucleons). We analyze the paramagnetic characteristics of the electron-positron plasma when exposed to an external primordial magnetic field.

hep-ph↗

arXiv2024

Self-consistent strong screening applied to thermonuclear reactions

Self-consistent strong plasma screening around light nuclei is implemented in the Big Bang nucleosynthesis (BBN) epoch to determine the short-range screening potential, $eϕ(r)/T \geq 1$, relevant for thermonuclear reactions. We numerically solve the non-linear Poisson-Boltzmann equation incorporating Fermi-Dirac statistics adopting a generalized screening mass to find the electric potential in the cosmic BBN electron-positron plasma for finite-sized $^4$He nuclei as an example. Although the plasma follows Boltzmann statistics at large distances, Fermi-Dirac statistics is necessary when work performed by ions on electrons is comparable to their rest mass energy. While strong screening effects are generally minor due to the high BBN temperatures, they can enhance the fusion rates of high-$Z>2$ elements while leaving fusion rates of lower-$Z\le 2$ elements relatively unaffected. Our results also reveal a pronounced spatial dependence of the strong screening potential near the nuclear surface. These findings about the electron-positron plasma's role refine BBN theory predictions and offer broader applications for studying weakly coupled plasmas in diverse cosmic and laboratory settings.

nucl-th↗

arXiv2024

Fermi-Dirac Integrals in Degenerate Regimes: A Novel Asymptotic Expansion

We characterize in a novel manner the physical properties of the low temperature Fermi gas in the degenerate domain as a function of temperature and chemical potential. For the first time we obtain low temperature $T$ results in the domain where several fermions are found within a de Broglie spatial cell. In this regime, the usual high degeneracy Sommerfeld expansion fails. The other known semi-classical Boltzmann domain applies when fewer than one particle is found in the de Broglie cell. We also improve on the understanding of the Sommerfeld expansion in the regime where the chemical potential is close to the mass and also in the high temperature regime. In these calculcations we use a novel characterization of the Fermi distribution allowing the separation of the finite and zero temperature phenomena. The relative errors of the three approximate methods (Boltzmann limit, Sommerfeld expansion, and the new domain of several particles in the de Broglie cell) are quantified.

cond-mat.quant-gas↗

arXiv2024

Elementary Particles and Plasma in the First Hour of the Early Universe

This dissertation aims to deepen the understanding of the primordial composition of the Universe in the temperature range 300 MeV>T>0.02 MeV. I exploit known properties of elementary particles and apply methods of kinetic theory and statistical physics to advance the understanding of the cosmic plasma. Within the Big Bang model, we begin by considering the Universe being a highly energetic fireball, an ultra-relativistic plasma exhibiting distinct properties. Fundamental particles such as quarks, leptons, and even heavier gauge bosons play a crucial role in the understanding of the early Universe. Our research focuses on the investigation of these fundamental particles as constituents of the dense Universe plasma during the epoch which transits from primordial quark-gluon plasma to the era of normal hadron matter, passing through the decoupling of neutrinos and addressing in detail the electron-positron antimatter plasma.

hep-ph↗

arXiv2023

Dynamic fermion flavor mixing through transition dipole moments

We show that Majorana neutrino flavor mixing can be driven by transition dipole moments in the presence of external electromagnetic fields. We demonstrate the sensitivity of the rotation mixing matrix to strong fields obtaining dynamical mass eigenstates in the two-flavor model. The three-flavor case and extensions to the quark sector are introduced.

hep-ph↗

arXiv2023

Electron-positron plasma in BBN: damped-dynamic screening

We characterize in detail the very dense $e^- e^+ γ$ plasma present during the Big-Bang Nucleosynthesis (BBN) and explore how it is perturbed electromagnetically by \lq\lq impurities, {\it i.e.\/}, spatially dispersed protons and light nuclei undergoing thermal motion. The internuclear electromagnetic screened potential is obtained (analytically) using the linear response approach, allowing for the dynamic motion of the electromagnetic field sources and the damping effects due to plasma component scattering. We discuss the limits of the linear response method and suggest additional work needed to improve BBN reaction rates in the primordial Universe. Our theoretical methods to describe the potential between charged dust particles align with previous studies on planetary and space dusty plasma and could have significant impact on interpretation of standard cosmological model results.

astro-ph.CO↗

arXiv2023

Matter-antimatter origin of cosmic magnetism

We explore the hypothesis that the abundant presence of relativistic antimatter (positrons) in the primordial universe is the source of the intergalactic magnetic fields we observe in the universe today. We evaluate both Landau diamagnetic and magnetic dipole moment paramagnetic properties of the very dense primordial electron-positron $e^{+}e^{-}$-plasma, and obtain in quantitative terms the relatively small magnitude of the $e^{+}e^{-}$ magnetic moment polarization asymmetry required to produce a consistent self-magnetization in the universe.

hep-ph↗

arXiv2023

A short survey of matter-antimatter evolution in the primordial universe

We offer a survey of the matter-antimatter evolution within the primordial Universe. While the origin of the tiny matter-antimatter asymmetry has remained one of the big questions in modern cosmology, antimatter itself has played a large role for much of the Universe's early history. In our study of the evolution of the Universe we adopt the position of the standard model $Λ$-CDM Universe implementing the known baryonic asymmetry. We present the composition of the Universe across its temperature history while emphasizing the epochs where antimatter content is essential to our understanding. Special topics we address include the heavy quarks in quark-gluon plasma (QGP), the creation of matter from QGP, the free-streaming of the neutrinos, the vanishing of the muons, the magnetism in the electron-positron cosmos, and a better understanding of the environment of the Big Bang Nucleosynthesis (BBN) producing the light elements. We suggest but do not explore further that the methods used in exploring the early Universe may also provide new insights in the study of exotic stellar cores, magnetars, as well as gamma-ray burst (GRB) events. We describe future investigations required in pushing known physics to its extremes in the unique laboratory of the matter-antimatter early Universe.

hep-th↗

arXiv2021

Cosmological Strangeness Abundance

We investigate the strange particle composition of the early Universe in the hadron epoch $T_h\approx 150\ge T\ge 10$\,MeV. We study strangeness yield in thermal and chemical equilibrium constrained by prescribed entropy per baryon in a charge neutral and strangeness neutral $\langle s-\bar s\rangle$ Universe. Turning to kinetic processes in a Hubble expanding Universe, we determine conditions at which individual strangeness producing reactions fall out of detailed balance between decay and back-reaction strangeness production rates in presence of decreasing temperature $T$; we allow for weak, electromagnetic, and strong interaction processes. The weak interaction $μ^\pm+ν_μ\rightarrow K^\pm$ freezeout is at $T_f^{K^\pm}=33.8\,\mathrm{MeV}$; the electromagnetic process $l^-+l^+\rightarrowϕ$ freezeout is at $T_f^ϕ=23\sim25\,\mathrm{MeV}$; and the hadronic reaction $π+π\rightarrow K$ freezeout is at $T_f^K=19.8\,\mathrm{MeV}$.

hep-ph↗

arXiv2021

Reactions Governing Strangeness Abundance in Primordial Universe

Strangness production processes can balance natural strangeness decay in the early hadronic Universe. Comparing to the characteristic Hubble time $1/H$, the reaction rates for $μ^\pm+ν_μ\rightarrow K^\pm$, $l^-+l^+\rightarrowϕ$, and $π+π\rightarrow K$ in sequence become slower than expansion rate at $T=33.9\,\mathrm{MeV}$, $T=25\,\mathrm{MeV}$ and $T=20\,\mathrm{MeV}$ respectively. This means that in the antibaryon annihilation epoch near to $T\simeq 40\,\mathrm{MeV}$ strangeness is in chemical equilibrium.

hep-ph↗

arXiv2021

The muon abundance in the primordial Universe

Muon abundance is required for the understanding of several fundamental questions regarding properties of the primordial Universe. In this paper we evaluate the production and decay rates of muons in the cosmic plasma as a function of temperature. This allows us to determine when exactly the muon abundance disappears. When the Universe cools below the temperature $kT_\mathrm{disappear}\approx 4.135$ MeV the muon decay rate overwhelms production rates and muons vanish quasi-instantaneously from the Universe. Interestingly, we show that at $T_\mathrm{disappear}$ the muon number is nearly equal to baryon abundance.

hep-ph↗

arXiv2020

Possibility of bottom-catalyzed matter genesis near to primordial QGP hadronization

We study bottom flavor abundance in the early Universe near to a temperature $T_\mathrm{H}\simeq150\,\mathrm{MeV}$, the condition for hadronization of deconfined quark-gluon plasma (QGP). We show bottom flavor abundance nonequilibrium lasting microseconds. In our study we use that in both QGP, and the hadronic gas phase (HG) $b$ and $\bar b$ quarks near $T_\mathrm{H}$ are bound in B-mesons and antimesons subject to $CP$ violating weak decays. A coincident non-equilibrium abundance of bottom flavor can lead to matter genesis at required strength: a) The specific thermal yield per entropy is $n_b^{th}/σ=10^{-10}\sim10^{-13}$. b) Considering time scales, millions of cycles of B-meson decays, and $b\bar b$-pair recreation processes occur.

hep-ph↗

arXiv2019

Lepton Number and Expansion of the Universe

We show that the non-integer effective number of neutrinos $N^{\mathrm{eff}}_ν$ can be understood as an effect of lepton $L$ asymmetry in the early Universe carried by the Dirac neutrino cosmic background. We show that $N_ν^{\mathrm{eff}}=3.36\pm0.34$ (CMB only) and $N_ν^{\mathrm{eff}}= 3.62\pm0.25$ (CMB and $H_0$) require a ratio between baryon number $B$ and lepton number to be $1.16 \times 10^{-9}\leqslant B/|L|\leqslant 1.51 \times 10^{-9}$. These values are close to the baryon-to-photon ratio $0.57\times 10^{-9}\leqslant B/N_γ\leqslant 0.67\times10^{-9}$. Thus instead of the usual $|L|\ll N_γ$ and $B\simeq |L|$, we propose to use $0.4 \leqslant |L|/N_γ\leqslant 0.52$ and $B\ll|L|$ as another natural choice, which resolves the tension between Planck-CMB and $H_0$ and leads to a non-integer value of $N_ν^{\mathrm{eff}}>3$.

hep-ph↗

arXiv2018

Temperature Dependence of the Neutron Lifespan

Current precision big bang nucleosynthesis (BBN) studies motivate us to revisit the neutron lifespan in the plasma medium of the early universe. The mechanism we explore is the Fermi-blocking of decay electrons and neutrinos by plasma. As result, neutrons live longer and we find a significant 6.4\% modification of neutron abundance in the BBN era arising from in plasma modification of the neutron lifetime. This effect can influence the final abundances of the light elements in BBN.

nucl-th↗