arXiv subjects

Yingnan Xu

Publications and source records attributed to Yingnan Xu.

7 recordsLinked to original sources

arXiv2026

Metric Source Completions and Integrability in Celestial Gravity

We evaluate local metric-source responses of celestial Einstein scattering in Weyl--Beltrami variables. Compact physical graviton packets retain the momentum-conservation distribution and its normal derivatives. For disjoint smooth Beltrami profiles, the complete reference same-chirality Ward response agrees with the differentiated quasiconformal source functional through quadratic order. Subtracting the symmetrized product response isolates a nonzero nonlinear coordinate contribution, detected by a linear normal packet independently of the quadratic normal coefficient. An analytic normal-profile subclass supports angular continuation on compact unpinched regions and permits evaluation of the MHV energy corner and relative Banerjee--Pasterski endpoint residue. For opposite helicities, consecutive soft theorems determine the energy and spin contributions to the full momentum distribution. A real Kawai--Lewellen--Tye channel gives its nonzero normal coefficient and the mixed Mellin divisor of a gravitational contact. We formulate the additional global Ward, contact and continuation conditions for a mixed metric Hessian. Reference scattering data, source transport and vacuum completion enter separately in this construction. In the scalar sector, an area-normalized relative determinant fixes the anomaly functional, and fixed-area harmonic combinations extract its Euler coefficient from local curvature terms of bounded derivative order. These calculations provide physical response data and local continuation domains for integrable celestial metric-source completions.

hep-th↗

arXiv2026

Large-$N$ Carrollian Thermodynamics from AdS Black-Hole Phase-Space Contractions

We develop a boundary large-$N$ interpretation of finite Carrollian black-hole thermodynamics and formulate its thermal Carrollian correlators in a celestial conformal-primary basis. The bulk input is a phase-space contraction, developed in earlier work, in which the time generator and Newton constant are scaled so that the extended AdS first law has a finite Carrollian limit. We show that this finite sector is naturally realized holographically as a double-scaled low-temperature, large-$N$ ensemble: the Carrollian temperature decreases while the effective number of boundary degrees of freedom grows, leaving the thermodynamic products in the first law finite. The large-$N$ dictionary is anchored by the standard $\mathrm{AdS}_5/\mathrm{CFT}_4$ normalization and by the Brown--Henneaux central charge in $\mathrm{AdS}_3/\mathrm{CFT}_2$. We construct the finite Carrollian Brown--York stress tensor on the contracted AdS boundary and show that its global energy charge reproduces the contracted bulk Hamiltonian. The boundary first law rewrites the bulk pressure term as a combined variation of spatial volume and holographic normalization, and identifies the Hawking--Page locus with the zero of the corresponding chemical potential conjugate to the holographic normalization. The same energy is the constant mode of a Carrollian time-shift charge, so the first law is the thermal zero-mode sector of a Carrollian time-shift Ward identity. Finally, we formulate the thermal celestial-basis correlators as positive/negative-frequency Mellin transforms of Carrollian spectral kernels.

hep-th↗

arXiv2026

Matter one-loop logarithms and homogeneous TTNC scale response of Lifshitz black branes

We compute the logarithmic one-loop matter contribution to the thermodynamics and homogeneous twistless torsional Newton--Cartan scale response of a four-dimensional Lifshitz black brane. The background is the neutral planar member of the analytic Einstein--Maxwell--dilaton Lifshitz black-brane family, while the quantum fields are treated as probes: a real scalar with arbitrary mass and nonminimal curvature coupling, a four-component Dirac spinor, and an Abelian Maxwell field with its Faddeev--Popov ghosts. For each spin sector, the logarithmic coefficient separates into a smooth radial heat-kernel contribution, governed by $\calC_1$, and a horizon-localized conical contribution, governed by $\calW_h$. This separation identifies which part of the matter one-loop logarithm is visible in the boundary Lifshitz/TTNC Ward identity and which part instead belongs to horizon replica entropy. The smooth coefficient $\calC_1$ controls the source-induced homogeneous projection of the TTNC Weyl Ward identity, namely the smooth boundary-source contribution to the Ward combination $z\epsilon-2p$, whereas the thermodynamic logarithmic entropy is controlled by $\calC_{\rm therm}=\calC_1+zL^2\calW_h$. We give closed expressions for $\calC_1$, $\calW_h$, and $\calC_{\rm therm}$ for the scalar, Dirac, and Maxwell probe sectors, identify the gauge-field contact contribution in the conical entropy, and verify that the smooth source response vanishes in the relativistic planar $z=1$ limit while the standard horizon heat-kernel entropy coefficient remains.

hep-th↗

arXiv2026

Extended Hamiltonian thermodynamics and Carroll contractions of AdS black holes

We study extended anti-de Sitter black-hole thermodynamics under correlated contractions of the time generator and Newton coupling. We relate the contraction parameter to physical units and distinguish variations within an equilibrium black-hole family from changes along the contraction. Starting from the magnetic Carroll Hamiltonian action, we derive the boundary identity with a variable cosmological constant and evaluate its energy, horizon and pressure contributions for Schwarzschild--anti-de Sitter geometries. We verify the spatial and lapse equations, retaining the boost connection in the coframe formulation. A three-form potential supplies a canonical variable conjugate to the cosmological constant. We compare this static boundary mechanics with Lorentzian thermodynamic contractions, whose common scaling of the work terms selects a finite Carroll branch. On this branch, temperature vanishes and entropy diverges while their conjugate product remains finite. The pressure and volume scalings depend on the chosen physical normalization. Charged, rotating and higher-dimensional families provide further thermodynamic tests, including the asymptotic frame and full thermodynamic volume for rotation. We use symbolic identities and numerical differentiation to verify the thermodynamic variations, resolve the conjugate contributions and check their scaling behaviour. These constructions relate extended static Carroll boundary mechanics to Lorentzian thermodynamic contractions and identify the phase-space conditions under which they correspond.

hep-th↗

arXiv2026

Global fits and the 95 GeV diphoton excesses in the Supersymmetric Georgi-Machacek Model

Recently the ATLAS and CMS experiments have reported modest excesses in the diphoton channel at around 95 GeV.~A number of recent studies have examined whether these could be due to an extended electroweak symmetry breaking (EWSB) sector, including the well known Georgi-Machacek (GM) model.~Here we examine whether the excesses can be explained by a light exotic Higgs boson in the \emph{Supersymmetric} GM (SGM) model which has the same scalar spectrum as the conventional GM model, but with a more constrained Higgs potential and the presence of custodial Higgsino fermions.~We perform a global fit of the SGM model including all relevant production and decay channels, some of which have been neglected in previous studies, which severely constrain the parameter space.~We find that the SGM model can fit the data if the LHC diphoton excesses at 95\,GeV are due to the lightest custodial singlet Higgs boson which contributes $(5-7)\%$ to EWSB, but \emph{cannot} accommodate the LEP $b\bar{b}$ excess, in contrast to other recent studies of the GM model.~Since the SGM model has a highly constrained Higgs potential, the rest of the mass spectrum is sharply predicted, allowing for targeted searches at the LHC or future colliders.~We also compare the SGM model with the non-supersymmetric GM model and identify how they can be distinguished at the LHC or future colliders.

hep-ph↗

arXiv2025

STEC-Net: A Spatiotemporal Graph Neural Framework for Community Discovery in Dynamic Social Networks

Community discovery is a central problem in the analysis of dynamic social networks. Traditional community discovery methods mainly focus on the formation and dissolution of links between nodes, and therefore often fail to capture the richer spatial structure and temporal dependency underlying network evolution. To address this limitation, we propose STEC-Net, a spatiotemporal graph neural framework for community discovery in dynamic social networks. STEC-Net integrates spatial structure and temporal dynamics within a unified embedding architecture. First, Graph Convolutional Networks (GCNs) are used to learn snapshot-level node representations from network topology. To adapt the spatial encoder to structural evolution, a GRU-based weight evolution mechanism is introduced to update the GCN parameters over time. Then, a second Gated Recurrent Unit (GRU) is employed to model temporal dependencies across snapshot embeddings and to learn spatiotemporal node representations. Finally, a Self-Organizing Map (SOM) is applied to the learned embeddings to cluster nodes and infer their community affiliations. Experiments on four types of dynamic networks show that STEC-Net consistently outperforms traditional community discovery methods in terms of purity, normalized mutual information, homogeneity, and completeness. These results demonstrate that STEC-Net can effectively uncover evolving community structures in dynamic social networks.

cs.SI↗

arXiv2024

Global Fits in the Supersymmetric Georgi-Machacek Model

We study a supersymmetric extension of the SM with Higgs triplets in the scalar sector. We begin with a review of the SM, particularly the Higgs mechanism. In the SM, the Higgs mechanism requires the presence of a complex Higgs doublet to break the electroweak symmetry and endow particles with a mass; this process is called Electroweak Symmetry Breaking. Although this is the simplest possibility, higher scalar representations may also contribute to the EWSB. The extent to which these higher representations contribute to EWSB is constrained by precise measurements of the $rho$ parameter. The model must predict $ρ=1$ at tree level. It is a fortuitous circumstance that simple doublet representations satisfy this requirement exactly. The underlying reason is that models with doublets satisfy an accidental custodial symmetry. Therefore, one can add any number of scalar doublets and still satisfy this experimental constraint. For higher representations, it is a bit trickier to maintain the custodial symmetry. We study in this work a supersymmetric model that incorporates triplet representations and satisfies the custodial symmetry. The non-supersymmetric Gorgi-Machacek model is one example of a custodial invariant model of SSB with Higgs triplets. However, the GM model has a fine-tuning problem beyond that of the SM. The solution to both issues is the Supersymmetric Custodial Triplet Model. The supersymmetric GM model arises as a low energy limit of the SCTM. It is this model that we study here. We make use of public code, GMCalc and HiggsTools, to perform global fits to the parameters of this model and obtain limits on model parameters at the $95%$ confidence level. For these hypothetical scalars, we identify the dominant decay channels and extract bounds on their branching ratios. We also examine the possible presence of a 95 GeV Higgs Boson in the SGM.

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