arXiv subjects

Tianjun Li

Publications and source records attributed to Tianjun Li.

At least 37 records · Page 2Linked to original sources

arXiv2026

The nano-hertz and milli-hertz stochastic gravitational waves in the minimal clockwork axion model

The clockwork framework can realize TeV-scale $U(1)_{PQ}$ symmetry breaking while generating a large axion decay constant $f_a$. We propose a minimal clockwork axion model with three scalar fields, in which two domain walls (DWs) have non-zero tension. The DW associated with one of the fields is formed following the Peccei-Quinn (PQ) symmetry breaking and subsequently collapses due to the potential bias induced by the QCD instanton. The nano-hertz stochastic gravitational waves (GWs) generated from this DW annihilation can be probed by Pulsar Timing Arrays experiments. In addition, the DW related to the other field is annihilated by a bias potential originating from higher-dimensional operators, producing a significant GW signal with a peak frequency around $9.41\times10^{-5}$ Hz, which can be detected by the LISA, Taiji, and TianQin experiments. Constraints on the model from SN1987, dark matter overproduction, Big Bang Nucleosynthesis, cosmic microwave background, and primordial black holes have been considered. The relic density of QCD axion dark matter can be explained through the misalignment mechanism.

hep-ph↗

arXiv2026

Unveiling a Universal Formalism for Quantum Entanglement in Arbitrary Spin Decays

We present a comprehensive theoretical framework for probing quantum entanglement in the decay angular distributions of a spin-$S$ particle-antiparticle pair $A\bar{A}$, where each particle decays sequentially into a two-body final state, $A\to B+C$ and $\bar{A}\to\bar{B}+\bar{C}$, with $B(\bar{B})$ carrying spin $b$ and $C(\bar{C})$ being spinless. Starting from the most general polarized initial state, we derive the fully differential angular distribution $\mathcal{W}(θ_1,θ_2,ϕ_1,ϕ_2)$ and identify observables $\langle\cos(2S(ϕ_1\mpϕ_2))\rangle$ whose expectation values directly depend on the entanglement-sensitive coefficients $\text{Re}\left(α_{-S,\mp S}α_{S,\pm S}^*\right)$ of the initial state. The proportionality factor $\mathcal{C}(S,b)$ in these relations is computed explicitly. For bosonic decays ($b=0,1,2,\ldots$), $\mathcal{C}(S,b)$ is universal and independent of decay dynamics; in particular, $\mathcal{C}(S,0)=1/2$ for any $S$, and $\mathcal{C}(1,1)=1/8$, matching known results for $W^+W^-$ decays. For fermionic decays ($b=\frac{1}{2},\frac{3}{2},\frac{5}{2}\ldots$), $\mathcal{C}(S,b)$ depends explicitly on the spin analysis powers $α_{A/\bar{A}}$, making entanglement extraction more decay-dependent. We further demonstrate, within the context of $e^+e^-\toγ^*\to A\bar{A}$ production, how $α_{A/\bar{A}}$ can be determined experimentally using specific angular observables restricted to the beam-axis region. Our results highlight the special role of bosonic decays in providing clean, model-independent tests of quantum entanglement at colliders, while outlining a pathway for entanglement measurement in fermionic cases through supplementary polarization information.

hep-ph↗

arXiv2026

Effect of accretion on scalar superradiant instability

Superradiance can lead to the formation of a black hole (BH) condensate system. We thoroughly investigate the accretion effect on the evolution of this system, and the gravitational wave signals it emits in the presence of multiple superradiance modes. Assuming the multiplication of the BH mass and scalar mass as a small number, we obtain the analytical approximations of all important quantities, which can be directly applied to phenomenological studies. In addition, we confirm that accretion could significantly enhance the gravitational wave (GW) emission and reduce its duration, and show that the GW beat signature is similarly modified.

gr-qc↗

arXiv2025

The Multi-Messenger Astroparticle Physics: the First Constraint on Light Millicharged Dark Matter via Time-Delay Analysis of GRB GW170817A

The multi-messenger astroparticle physics provides a new approach to probe the new physics beyond the Standard Model. We propose to probe the light dark matter which can interact with electromagnetic interaction. To be concrete, we derive the new constraint on the millicharged dark matter from the multi-messenger observations of GW170817. In the neutron star merger event GW170817, the first detection of a gamma-ray burst (GRB) delayed by approximately 1.7 seconds relative to the gravitational wave emission was observed. Utilizing this delay, we constrain the parameter space of the millicharged dark matter within the large-scale structure of the Universe. For dark matter mass below $10^{-15}$ eV, the parameter $ε$ is constrained to be less than $10^{-14}$, representing the most stringent limits achieved to date.

hep-ph↗

arXiv2025

Generalized Three-Family Supersymmetric Pati-Salam Models from Type IIA Intersecting D6-Branes

Generalizing three-family chiral fermion conditions to $I_{ac}=-(3+h)$ and $I_{ac'}=h$, with positive integer $h$, we extend the landscape of three-family ${\cal N}=1$ supersymmetric Pati-Salam models in a broader region. Differing from the former investigation with $I_{ac}=-3$ and $I_{ac'}=0$, we do not restrict that the $a$ stack of D6-branes must be parallel to the orientifold image of the $c$-stack along one of the three two-tori. In this investigation, without the simple parallel construction, we find four new classes of supersymmetric Pati-Salam models that are allowed by the extended three generation condition with $I_{ac}=3, I_{ac'}=-6$ and $I_{ac}=-1, I_{ac'}=-2$ through the intersections of $a$- and $c/c'$-branes. Moreover, with the $SU(2)_{L'}$ gauge coupling realized from $SU(2)_{L_1}\times SU(2)_{L_2}$ symmetry breaking, the canonical normalization requirement of the gauge kinetic term provides an alternative approach that can be imposed before the renormalization group equation evolution for $SU(2)_{L'}$ gauge coupling. This turns out to be an effective mechanism to realize the string-scale gauge coupling relation, especially for the new supersymmetric Pati-Salam models with large $g_b/g_a$ ratio. We show that this symmetry-breaking modified renormalization group evolution can highly suppress $g_b/g_a$, and finally realizes string-scale gauge coupling relations for the extended supersymmetric Pati-Salam models as well.

hep-th↗

arXiv2025

Probing Primordial Black Hole Formation from Domain Wall Isocurvature Perturbations: Constraints and Implications

Domain walls are topological defects produced by the spontaneous symmetry-breaking of discrete symmetry during cosmological phase transitions. Domain walls can significantly contribute to the energy density in the late-evolution stage. We propose that the density perturbations from the fluctuations in the number density of the domain walls could collapse to form primordial black holes. This mechanism becomes effective when the domain wall energy density ratio to that of the radiation reaches about 0.1 in the radiation-dominated Universe. We find that models with $Z_2$ symmetry are excluded for interpreting pulsar timing array observations on the nano-Hz gravitational wave background since this model's domain wall number density fluctuations could lead to an overabundance of the primordial black holes. Moreover, the models, which generate approximately $N\sim 10$ domain walls from the spontaneous breaking of a discrete $Z_N$ symmetry, are also subject to stringent constraints due to the overproduction of primordial black holes.

astro-ph.CO↗

arXiv2025

Nuclear Ptychoscopy: A Ptychographic Framework for Nuclear Spectroscopy

Accessing both amplitude and phase of nuclear response functions is central to fully characterizing light-matter interactions in the X-ray-nuclear regime. Recent work has demonstrated phase retrieval in two-dimensional time- and energy-resolved spectra, establishing the feasibility of phase-sensitive nuclear spectroscopy. Here, we introduce Nuclear Ptychoscopy, a ptychographic framework that adapts algorithms from coherent diffractive imaging to nuclear spectroscopy, enabling reconstruction of the complex response function by exploiting redundancy in two-dimensional spectra. We develop three complementary reconstruction schemes tailored to distinct experimental scenarios: reconstruction with a known analyzer response, blind reconstruction, and reconstruction incorporating partial prior information. In parallel, we develop geometric analysis techniques that elucidate algorithmic behavior and contribute new tools to ptychography. The framework is validated through experimental data and simulations, demonstrating its versatility across diverse nuclear spectroscopy scenarios and bridging nuclear spectroscopy with ptychography. Beyond advancing quantitative nuclear spectroscopy, our framework opens new opportunities for metrology, coherent control, and quantum applications in the X-ray-nuclear regime.

physics.ins-det↗

arXiv2025

High-Quality Axion Models with the Anomalous $U(1)_X$ Gauge Symmetry

We propose the generic high-quality axion models with anomalous $U(1)_X$ gauge symmetry and vector-like particles. We briefly review the gauge anomaly cancellations via the Green-Schwarz mechanism, study the breaking of the $U(1)_X$ gauge symmetry, as well as derive the Nambu-Goldstone boson, Peccei-Quinn (PQ) axion, and axion decay constant in general. The high-dimensional operators, which break the $U(1)_{PQ}$ global symmetry, have dimension eleven or higher due to the anomalous $U(1)_X$ gauge symmetry, and thus the axion quality problem is solved. In particular, unlike the high-quality axion models with anomaly free $U(1)$ gauge symmetry, we only need to introduce two pairs of vector-like particles. To be concrete, we present three specific models with two pairs of vector-like particles. We show that gauge anomalies in all three models can be canceled via the Green-Schwarz mechanism. To achieve gauge coupling unification, we need to introduce additional vector-like particles only in Model I. We find that gauge coupling unification is achieved at the unification scale around $10^{16}$ GeV with a relative error of less than 1\%. Notably, gauge coupling unification in Model II is achieved naturally with the smallest relative error of 0.1\%.

hep-ph↗

arXiv2025

New Physics Search at the CEPC: a General Perspective

The Circular Electron-Positron Collider (CEPC), a proposed next-generation Higgs factory, provides new opportunities to explore physics beyond the Standard Model (SM). With its clean electron-positron collision environment and the ability to collect large samples of Higgs, W, and Z bosons, the CEPC enables precision measurements and searches for new physics. This white paper outlines the CEPC's discovery potential, including studies of exotic decays of the Higgs, Z, and top quarks, dark matter and dark sector phenomena, long-lived particles, supersymmetry, and neutrino-related signatures. Advanced detector technologies and reconstruction techniques, such as one-to-one correspondence reconstruction and jet origin identification, significantly improve sensitivity to rare and weakly interacting processes. The CEPC is particularly well suited to probe the electroweak phase transition and test models of electroweak baryogenesis and dark sector interactions. In addition, global fit analyses highlight the CEPC's complementary role in constraining a wide range of new physics scenarios. These features position the CEPC as a powerful tool for exploring the next frontier in fundamental particle physics in the post-Higgs discovery era.

hep-ex↗

arXiv2025

The Light Neutralino Dark Matter at Future Colliders in the MSSM with the Generalized Minimal Supergravity (GmSUGRA)

We perform a detailed investigation of light right-handed slepton bulk regions, together with the Higgs- and $Z$-resonance regimes, in the Minimal Supersymmetric Standard Model (MSSM) with Generalized Minimal Supergravity (GmSUGRA), focusing on the higgsino mass parameter scenario $μ< 0$, given that the anomalous magnetic moment of the muon may now be consistent with the Standard Model (SM) prediction. A systematic numerical exploration of the parameter space is carried out, where the bulk region is conservatively defined by the mass-splitting ratio \[ \mathcal{R}_{\tildeϕ} = \frac{m_{\tildeϕ} - m_{\tildeχ_1^0}}{m_{\tildeχ_1^0}} \gtrsim 10\%. \] In particular, we analyze the case in which the right-handed stau ($\tildeτ_R$) emerges as the Next-to-Lightest Supersymmetric Particle (NLSP). We uncover a sizeable parameter space consistent with current experimental bounds, including limits from LHC supersymmetry searches, the Planck 2018 relic density measurement, and direct detection constraints on neutralino-nucleon scattering. This region naturally accommodates bulk annihilation channels mediated by right-handed sleptons. We obtain robust upper bounds on the masses of the lightest neutralino, $m_{\tildeχ_1^0} \lesssim 143~\text{GeV}$, and the right-handed stau, $m_{\tildeτ_R} \lesssim 158~\text{GeV}$. The identified bulk region lies within the prospective reach of forthcoming dark matter direct detection facilities such as LUX-ZEPLIN, as well as future high-energy $e^+e^-$ colliders including FCC$_{\text{ee}}$ and CEPC. Conversely, scenarios with the right-handed selectron as the NLSP have already been excluded by current LHC data. Furthermore, the parameter space consistent with our findings yields contributions to the anomalous magnetic moment of the muon, $a_μ= (g_μ- 2)/2$.

hep-ph↗

arXiv2025

Three-family supersymmetric Pati-Salam models from intersecting D6-branes on rigid cycles

Intersecting D6-brane models without discrete torsion typically suffer from unstabilized open string moduli, arising from D-brane positions and Wilson lines. These moduli generate additional massless adjoint fields, obstructing the realization of negative beta functions necessary for asymptotic freedom unless they are decoupled around string scale. A viable solution involves utilizing rigid cycles, which eliminate these unwanted adjoint fields. In this work, we for the first time present a class of consistent three-family supersymmetric Pati-Salam models from rigid intersecting D6-branes on the factorizable $\mathbb{T}^6/(\mathbb{Z}_2 \times \mathbb{Z}_2^\prime)$ orientifold with discrete torsion. These models satisfy all the known consistency conditions, including $\mathcal{N}=1$ supersymmetry, K-theory constraints, tadpole cancellation, and recent swampland bounds on the maximal gauge group rank. We provide detailed particle spectra, analyze their phenomenological implications, and discuss the decoupling of exotic states through strong dynamics in the hidden sector.

hep-th↗

arXiv2025

Primordial Black Holes from Domain Wall Density Fluctuations: Bridging Gravitational Wave Observations Across Two Frequency Bands

We propose a novel mechanism for the formation of primordial black holes by demonstrating that the delayed production of isocurvature perturbations resulting from Poisson fluctuations within the domain wall network can lead to collapse and the formation of primordial black holes during the horizon crossing of domain walls. Our findings establish a statistical relationship between the number of domains and the power spectrum of the perturbations. This relationship can be employed to constrain the symmetry of the model in light of the potential overabundance of primordial black holes. Furthermore, by incorporating the effects of accretion, we demonstrate that the annihilation of the domain wall network at the QCD scale may provide a plausible common origin for gravitational wave observations across two distinct frequency bands.

astro-ph.CO↗

arXiv2025

Revisiting the Electroweak Supersymmetry from the Generalized Minimal Supergravity

We explore the Electroweak Supersymmetry (EWSUSY) scenario within the Minimal Supersymmetric Standard Model (MSSM) under the Generalized Minimal Supergravity (GmSUGRA) framework, given that the anomalous magnetic moment of the muon may now be consistent with the Standard Model (SM) prediction, we consider both signs of the Higgsino mass parameter, $μ< 0$ and $μ> 0$. A comprehensive scan of the parameter space is performed, subject to the experimental constraints from the LHC SUSY searches, Planck 2018 relic density, and LUX-ZEPLIN (LZ) direct detection limits. We identify the viable regions featuring neutralino dark matter production via coannihilation with stau, chargino, stop, sbottom, and gluino, as well as through $A$-funnel, Higgs-resonance, and $Z$-resonance mechanisms. Notably, the $μ< 0$ scenario yields a broader allowed parameter space, including for the first time sbottom-neutralino coannihilation solutions in GmSUGRA, which are absent for $μ> 0$. While the Higgs-pole and $Z$-pole regions for $μ> 0$ are largely excluded by the current LZ bounds, substantial viable regions remain for $μ< 0$. Gluino coannihilation scenarios are strongly constrained by the current LHC data. The characteristic mass ranges of interest include sbottoms (0.7-1.3~TeV), stops (up to 1.0~TeV for $μ> 0$ and 1.3~TeV for $μ< 0$), staus and charginos (up to 1.5~TeV), and pseudoscalar Higgs bosons in the $A$-funnel (0.4-1.4~TeV). Moreover, the supersymmetric contributions to the muon anomalous magnetic moment remain within a $2σ$ deviation from the SM prediction. And our findings suggest that significant portions of the parameter space can be probed at the future LHC SUSY searches and upcoming dark matter direct detection experiments.

hep-ph↗

arXiv2025

Explanations of the Tentative New Physics Anomalies and Dark Matter in the Simple Extension of the Standard Model (SESM)

We revisit the Simple Extension of the Standard Model (SESM), which can account for various tentative new physics anomalies and dark matter. The B physics anomalies, muon anomalous magnetic moment, and dark matter can be explained already in SESM. In this work, we study the unitarity constraint on this model and comment the parameter space on the edge of unitarity bounds. Besides, the complete scalar potential is considered which is needed to address the $W$ boson anomaly and more dark matter (co-)annihilation processes are discussed. We perform a systematic study, and find the viable parameter space which can explain these anomalies and evade all the current experimental constraints.

hep-ph↗

arXiv2025

Three family supersymmetric Pati-Salam model from rigid intersecting D6-branes

We construct, for the first time, a three-family $\mathcal{N}=1$ supersymmetric Pati-Salam model from rigid intersecting D6-branes on a factorizable $\mathbb{T}^6/(\mathbb{Z}_2\times \mathbb{Z}_2')$ orientifold with discrete torsion. The factorizable geometry allows for explicit control over rigid cycles and moduli stabilization. We can break the Pati-Salam gauge symmetry down to the Standard Model (SM) gauge symmetry via the supersymmetry preserving Higgs mechanism, generate the SM fermion masses and mixings, and break the supersymmetry via gaugino condensations in the hidden sector.

hep-th↗

arXiv2025

Revisiting the Realistic Intersecting D6-Brane Model with positive and negative μ Terms

In light of current constraints from supersymmetry (SUSY) searches within the LHC, as well as findings from direct dark matter detection experiments such as LUX-ZEPLIN (LZ), we revisit the three-family Pati-Salam model derived from intersecting D6-branes in Type IIA string theory compactified on the $T^6/(\mathbb{Z}_2 \times \mathbb{Z}_2)$ orientifold, known for its realistic low-energy phenomenology. Since the muon anomalous magnetic moment might be in accordance with the Standard Model prediction, we conduct a comprehensive scan over the model's parameter space for each sign of the Higgsino mass parameter, $μ< 0$ and $μ> 0$. We find that the gravitino mass is typically greater than 1.5 TeV in both scenarios while simultaneously satisfying the LHC SUSY bounds, B-physics observables, and the Higgs mass constraint. Within the experimentally viable region of the parameter space, the sparticle mass spectra fall within the following ranges: gluinos lie in the range 2-18 TeV; first- and second-generation squarks and sleptons span 3-16 TeV and 1-6 TeV, respectively. For third-generation sfermions, the lightest stop, which can satisfy the dark matter relic density via neutralino-stop coannihilation consistent with the \textit{Planck} 5$σ$ bounds, has a mass in the range 0.5-1.2 TeV. The lightest neutralino can be as heavy as 2.9 TeV. Additionally, the lightest stau can be as light as 200 GeV or as heavy as 5.2 TeV. We identify several viable mechanisms, including multiple coannihilation channels and resonance mechanisms, by which the observed dark matter relic abundance is successfully realized.

hep-ph↗

arXiv2025

Family Unification in $SO(16)$ Grand Unification

We propose a unified model for the three Standard Model (SM) gauge symmetries and $SU(3)$ family symmetry based on $SO(16)$ grand unified gauge symmetry on six-dimensional (6D) spacetime. In this model, three chiral generations of quarks and leptons are unified into a 6D Weyl fermion in the spinor representation of $SO(16)$. The 6D $SO(16)$ gauge anomaly is canceled by the vectorlike nature of the model, and the 4D gauge anomalies are canceled by introducing suitable 4D localized fermions at the fixed point. The 4D gauge coupling constant of $SO(16)$ has the property of becoming weaker at high energies.

hep-ph↗

arXiv2025

Quantum Entanglement Theory and Its Generic Searches in High Energy Physics

We propose a new formalism for quantum entanglement (QE), and study its generic searches at the colliders. For a general quantum system with $N$ particles, we show that the quantum space (the total spin polarization parameter space) is complex projective space, and the classical space (the spin polarization parameter space for classical theory) is the cartesian product of the complex projective spaces. Thus, the quantum entanglement space is the difference of these two spaces. For the $ff$, $AA$, $Af$, $fff$, and $ffA$ systems, we propose their discriminants $Δ_i$. The corresponding classical spaces are the discriminant locus $Δ=0$ for $ff$ system, and intersections of the discriminant loci $Δ_i=0$ for $AA$, $Af$, $fff$, and $ffA$ systems in the quantum space. In particular, for two fermion $ff$ system, we prove that our discriminant criterion is equivalent to the original Peres-Horodecki criterion and the CHSH criterion. And thus our quantum entanglement space is indeed Bell non-local. With the collider searches, we can reconstruct the discriminants from various measurements, and probe the quantum entanglement spaces via a fundamental approach at exact level. In addition, for the specific approach, we present a comprehensive framework to detect quantum entanglement in high-energy multi-particle systems, spanning fermion pairs ($t\bar{t}$, $τ^{+}τ^{-}$), bosonic pairs ($W^{-}W^{+}$), and hybrid or three-body systems ($W^{-}t$, $ttt$, $t\bar{t}W^{-}$), by diverse observables through angular correlations in decay products. These results establish model-independent methodologies for probing QE across collider experiments, bridging quantum information principles with high-energy phenomenology, while offering novel pathways to explore exotic particles and quantum properties in multi-particle systems.

hep-ph↗