Fri·Dec 5, 2025Friday·December 5, 2025

1. 01*

   Z' portal dark matter from post-inflationary reheating: WIMPs, FIMPs, and UFOs

   Stephen E. Henrich🇺🇸 · Yann Mambrini🇫🇷 · Keith A. Olive🇺🇸

   We investigate the production of dark matter (DM) via a heavy $Z^{\prime }$ mediator during the post-inflationary reheating epoch. In particular, we study production from three mechanisms which are smoothly connected to one another: WIMP-like freeze-out, FIMP-like freeze-in, and ultra-relativistic freeze-out (UFO). This is the first systematic study of $Z^{\prime }$ portal DM which includes UFO. We find that much of the available parameter space for keV to TeV DM lies in the UFO regime for $1\text{ TeV}\lesssim M_{Z^{\prime }}\lesssim 1\text{ PeV}$. When the mediator mass $M_{Z^{\prime }}$ is greater than both the DM mass and the reheating temperature, UFO is a robust mechanism for producing cold DM. Although UFO DM is initially "hot" after freeze-out, it can easily become cold before structure formation if freeze-out occurs during post-inflationary reheating. Compared to standard freeze-in, UFO can accommodate significantly stronger interaction strengths (stronger couplings and/or smaller mediator masses).

   hep-phastro-ph.COJCAP(2026)·8 citations
2. 02*

   Gravitational Waves from Isocurvature Perturbations of Spectator Scalar Fields

   Marcos A. G. Garcia🇲🇽 · Sarunas Verner🇺🇸

   We present a mechanism for gravitational wave (GW) production from isocurvature perturbations in spectator scalar fields during inflation. These energetically subdominant fields develop blue-tilted power spectra through inflationary dynamics, generating second-order scalar perturbations that source a stochastic GW background. The mechanism naturally satisfies CMB constraints at large scales while producing enhanced signals at smaller scales across a broad frequency range $10^{-20}-1$ Hz. We perform comprehensive numerical and analytical calculations of the complete isocurvature spectrum evolution, including gravitational particle production, reheating dynamics, and scalar-induced GW generation. For spectator fields with effective masses $0.5\lesssim m_{\chi ,\mathrm{eff}}/H_I$, the resulting GW energy density reaches ${\Omega }_{\text{GW}}{h}^2\sim 10^{-20}$-$10^{-12}$, accessible to pulsar timing arrays, space-based interferometers, and next-generation CMB experiments. Our analysis reveals that GW-induced constraints exceed current isocurvature bounds. We examine both unstable (curvaton-like) and stable (dark matter) spectator fields, demonstrating strong sensitivity to reheating temperature, inflaton-spectator coupling, and decay dynamics. This framework establishes isocurvature-sourced GWs as a powerful probe of early universe physics, enabling simultaneous constraints on inflationary dynamics, dark matter production, and reheating through coordinated multi-frequency GW observations.

   hep-phastro-ph.COgr-qcJCAP(2026)·4 citations
3. 03*

   A thrust to trust minimum thrust

   Matteo Cacciari🇫🇷

   We determine the minimum value of thrust for a number of N-particle configurations. For N=5 in three dimensions an exact result is found for the first time. For larger N we obtain numerical results through optimisation. When a definite value cannot be reliably identified, the results are analysed in the context of Extreme Value Theory, using a Maximum Likelihood Estimate and a Bayesian analysis. Results are given for three spatial dimensions, two dimensions, and selected cases in d dimensions.

   hep-phActa Phys.Polon.B(2026)·3 citations
4. 04*

   Powerful Yukawas

   Timothy Cohen🇨🇭 · Matthew McCullough🇨🇭 · Neal Weiner🇺🇸

   We introduce a class of models where the masses of the light Standard Model fermions are due to an Effective Field Theory operator that appears beyond dimension-4 in the power counting expansion, resulting in a `Powerful Yukawa'. The effective Yukawa coupling structure is UV-completed using a collective symmetry breaking pattern in the flavour sector, which we dub `Sprouted Symmetry Breaking.' The irreducible signature is an enhanced Higgs coupling to the light Standard Model fermions.

   hep-ph1 citation
5. 05*

   LHC Shines on Positivity

   Zhen Liu🇺🇸 · Kun-Feng Lyu🇺🇸 · Tong Arthur Wu🇺🇸

   We show that hadron colliders have an excellent reach for positivity tests on a class of diphoton operators. Due to the helicity selection rules, the relevant dimension-6 operators either do not contribute or are highly constrained by other experimental observables. We show, for the first time, that the LHC can probe the positivity of the dimension-8 operators involving colored particles. The kinematic differential distributions of the diphoton final states are exploited to perform the ${\chi }^2$ analysis. Through a global fit, the effective scale for these operators can be inclusively probed up to around 2 TeV at HL-LHC and over 5 TeV at future 100 TeV FCC-hh at 95% C.L., providing a powerful test of the positivity bounds up to multi-TeV scale.

   hep-ph3 citations
6. 06*

   New avenues for tau flavor violation

   Julian Heeck🇺🇸

   I present a concise overview of tau flavor violation and the broad opportunities it offers, with a focus on non-standard decay channels and their underlying theoretical motivations.

   hep-phhep-ex0 citations
7. 07*

   Nucleon to Roper transition amplitudes and electromagnetic form factors

   G. Ramalho🇰🇷

   The second excitation of the nucleon, the Roper, has properties differentiated from other low-lying nucleon resonances. Their properties challenge our understanding of the structure of the baryons in terms of the degrees of freedom from QCD. In the present work we discuss the properties of the Roper resonance and the nucleon to Roper electromagnetic transition, based on the quark degrees of freedom, that are expected to dominate for large square momentum transfer $Q^2$. We also discuss the analytic structure of the transition amplitudes in the low-$Q^2$ region, and how the contributions of baryon-meson states can help to describe the low and intermediate $Q^2$ data, and the nature of the Roper.

   hep-phhep-exhep-latnucl-ex+1Acta Phys.Polon.B(2026)·2 citations
8. 08*

   Probing Hard Scattering Processes via Multiple Weak Gauge Boson Production at the Future Colliders

   Ijaz Ahmed🇵🇰 · M.S. Amjad🇵🇰 · Jamil Muhammad🇰🇷

   One of the possible ways to detect the new physics phenomena particles is to investigate the weak gauge boson production as a result of hadron-hadron scattering. This study comprises the production of multiple weak gauge bosons as a result of hard scattering between the proton-proton beams at multi-TeV energies and integrated luminosity $\mathcal{L}=$ 3000 $f{b}^{-1}$. The effective production cross-sections for pair, triple, and quartic scattering mechanisms have been computed as a function of $\sqrt{s}$. The center of mass energy has been varied from 8 TeV to 100 TeV to encompass the future collider capabilities. Out of all the studied processes, the triple scattering process $W^{+}{W}^{-}{W}^{+}$ has been chosen as the signal process based on the dominant cross-section. The background channels ZZZ, ZZZZ, $W^{-}ZZ$, $W^{+}ZZ$, $W^{+}{W}^{-}Z$, $W^{+}{W}^{-}ZZ$, $W^{+}{W}^{-}{W}^{+}{W}^{-}$, having comparatively lower cross-sections, have been selected from possible scattering mechanisms to investigate the effect of higher luminosity on the low production cross-section processes. We have investigated the different decay modes. For both lepton and hadron-specific decays of W and Z, the cumulative efficiencies for each signal and background process have been computed. In this study, we have successfully demonstrated an effective methodology for background suppression by systematically optimizing the signal-to-background ratio. The results indicate that, despite lower cross-sections for higher-order scattering, the distinct kinematic features enable effective signal isolation at future colliders.

   hep-ph0 citations
9. 09*

   Spontaneous Symmetry Breaking and the Higgs Mechanism

   Gustavo Burdman🇧🇷

   The Higgs sector of the standard model of particle physics plays a central role in the generation of all the masses of elementary particles known so far. Here we give a pedagogical introduction to all the elements leading ot the Higgs mechanism and the Higgs boson, starting with the spontaneous symmetry breaking of global symmetries and the Goldstone theorem. We then consider the case of gauge symmetries, i.e. the Higgs mechanism, and its application to the electroweak sector of the standard model. We close with a reflection on the possible open questions that the very introduction of the Higgs sector in the standard model posses.

   hep-phhep-ex0 citations
10. 10*

    The next-to-next-to-leading-order QCD corrections to $e^{+}{e}^{-}\to {\eta }_c/{\chi }_{cJ}+\gamma$ at B factories

    Cong Li🇨🇳 · Wen-Long Sang🇨🇳 · Hong-Fei Zhang🇨🇳

    We investigate the processes $e^{+}{e}^{-}\to {\eta }_c+\gamma$ and $e^{+}{e}^{-}\to {\chi }_{cJ}+\gamma$ at B factories within the NRQCD factorization framework, computing the corresponding helicity amplitudes through $\mathcal{O}({\alpha }_s^2)$. The short-distance coefficients are obtained as series expansions in $r=\frac{4m_c^2}{s}$ around $r=0,1/3,2/3,1$, using the method of differential equations. By combining the expansions from all four points, we construct composite asymptotic expressions that reproduce the exact results accurately over the full range $0\le r\le 1$, with relative errors below $0.1\%$ over most of the domain and remaining under $1\%$ elsewhere. Analytic expressions for the leading and next-to-leading logarithmic terms are extracted in the limit $r\to 0$. Using these results, we compute the unpolarized cross sections and observe that the perturbative corrections are small for ${\chi }_{c0}+\gamma$, moderate for ${\chi }_{c1}+\gamma$, and substantial for ${\eta }_c+\gamma$ and ${\chi }_{c2}+\gamma$. Theoretical prediction for ${\chi }_{c1}+\gamma$ is consistent with the {\tt Belle} measurement within $2\sigma$, showing good agreement between theory and experiment. We also predict the angular distribution parameters ${\alpha }_{\theta }^H$, which are insensitive to NRQCD matrix elements and exhibit small theoretical uncertainties. These parameters further display good stability across different perturbative orders. With the high luminosity anticipated at {\tt Belle 2}, future experimental measurements will thus provide a clear test of NRQCD factorization.

    hep-phhep-exJHEP(2026)·5 citations
11. 11*

    Optimal Transport Event Representation for Anomaly Detection

    Tianji Cai🇺🇸 · Aditya Bhargava🇺🇸 · Benjamin Nachman🇺🇸

    We introduce optimal transport (OT) as a physics-based intermediate event representation for weakly supervised anomaly detection. With only $0.5\%$ injection of resonant signals in the LHC Olympics benchmark datasets, the OT-augmented feature set achieves nearly twice the significance improvement of the standard high-level observables using an idealized setup, while end-to-end deep learning on low-level four-momenta is less effective in this low-signal regime. The observed gains persist across signal types and classifiers considered in this study, suggesting that structured, physics-informed representations can provide a useful complement to existing approaches for anomaly detection.

    hep-phhep-exPRD(2026)·1 citation
12. 12*

    Pion physics with dressed quark-gluon vertices

    Mauricio N. Ferreira🇨🇳 · Angel S. Miramontes🇪🇸 · Jose M. Morgado🇪🇸 · Joannis Papavassiliou🇪🇸 · Jan M. Pawlowski🇩🇪

    Recently, a theoretical framework was set up in [1], which allows for the symmetry-preserving inclusion of full quark-gluon vertices in the description of the meson dynamics. In the present work, we develop a special truncation within this approach, which leads to a tractable set of functional equations that satisfy the fundamental chiral Ward-Takahashi identities. Specifically, the truncation allows us to simplify considerably the quark-gluon Schwinger-Dyson equation, without significant loss of quantitative accuracy. Importantly, this implies a substantial reduction of complexity of the renormalized Bethe-Salpeter equation: it is composed by a pair of one-loop diagrams that contain the full quark-gluon vertex, and a single two-loop diagram that is instrumental for the masslessness of the pion in the chiral limit. A detailed numerical analysis reveals that the incorporation of the aforementioned two-loop diagram is instrumental for the corresponding eigenvalue to reach unity. The key relation between the quark mass function and the pion wave function is shown to be satisfied to within the numerical precision of the loop integrals, which is at the level of about one percent or better. The field-theoretic ingredients required for the extension of this analysis beyond the chiral limit are briefly discussed.

    hep-phhep-lathep-thEPJC(2026)·8 citations
13. 13*

    Towards a Fully Automated Differential ${\text{NNLO}}_{\text{EW}}$ Generator for Lepton Colliders

    Alan Price🇵🇱 · Frank Krauss🇬🇧

    Future proposed lepton collider experiments will reach unprecedented levels of accuracy. To ensure the success of these experiments, and to fully exploit their wealth of data, the precision of theory calculations must reach comparable or even better levels. One bottleneck in achieving this precision target lies in the systematic, process-independent inclusion of higher-order corrections at Next-to-Next-to-Leading Order in the electroweak coupling ${\text{NNLO}}_{\text{EW}}$ while ensuring the correct matching with modern all-orders resummation techniques. Here, we present a solution to this problem, based on the Yennie-Frautschi-Suura theorem, which employs a local infrared (IR) subtraction to remove divergences and its matching to an all-order resummation of the soft and soft-collinear logarithms.

    hep-phhep-exhep-thPRD(2026)·5 citations
14. 14*

    Isolating chirality-breaking SMEFT operators with Drell-Yan angular analysis

    Samuele Grossi🇮🇹 · Xu Li🇮🇹 · Lorenzo Rolla🇮🇹 · Riccardo Torre🇮🇹

    We present a comprehensive strategy to isolate the effect of a class of chirality-breaking interactions in the Standard Model Effective Field Theory (SMEFT) by exploiting Drell-Yan angular analysis and the violation of the Lam-Tung relation. Unlike most SMEFT interpretation of Drell-Yan measurements, dominated by growing-with-energy effects generated by the interference of SMEFT-induced and SM amplitudes, this method isolates operators that contribute only quadratically in the Wilson coefficients, allowing for an independent probe of non-interfering operators. Denoting with $v$ the electroweak vev, with $\sqrt{s}$ the center-of-mass energy, and with $\Lambda$ the scale of new physics, the non-interfering contributions to the amplitude generated by the chirality-breaking operators can be proportional to $v\sqrt{s}/{\Lambda }^2$ or $s/{\Lambda }^2$. We argue that these two classes can be further distinguished by analyzing the angular observables of the lepton pair in the transverse momentum and in the invariant mass distribution of the lepton pair. We therefore present an analysis of the lepton-pair angular observables in both these distributions. Based on a precise estimate of the Standard Model contribution to the relevant observables for the $pp\to l^{+}{l}^{-}+X$ process up to $O({\alpha }_S^2)$, we present realistic projections for the sensitivity of the LHC with $300$ fb${}^{-1}$ and for the HL-LHC with $3$ ab${}^{-1}$ to chirality-breaking interactions, demonstrating that angular observables provide an independent and clean handle on SMEFT effects, especially in regions where the Standard Model contribution is naturally suppressed thanks to the Lam-Tung relation. This analysis becomes crucial to go beyond single parameter global fits, since it helps breaking degeneracies with chirality preserving operators and to disentangle overlapping directions in the EFT parameter space.

    hep-phhep-exJHEP(2026)·1 citation
15. 15*

    Geometry of particle emission in UrQMD Ar+Sc collisions at SPS energies

    Barnabas Porfy🇭🇺 · Mate Csanad🇭🇺

    Over the past few decades, progress in femtoscopy has been driven by the interplay between experimental measurements and theoretical calculations. Measurements provide data to support the theory, while theoretical predictions guide new measurements. In the recent decade, several experiments have confirmed that the two-particle pion-emitting source is well described by Lévy alpha-stable distributions. To enable theoretical interpretation, phenomenological simulations have been done at RHIC and LHC energies, in large systems such as Au+Au or Pb+Pb, using various available heavy-ion collision models. However, such simulations have not been done in intermediate systems. In this paper, we investigate three-dimensional two-pion pair source distributions from ${}^{40}$Ar+${}^{45}$Sc central collisions at SPS energies, generated with the Ultra-Relativistic Quantum Molecular Dynamics Monte-Carlo event generator. Supplemented by a validation of the simulated hadronic spectra, we find that the pair source can be described with Lévy-stable distributions. We subsequently interpret the physical meaning of the extracted Lévy parameters corresponding to the spatial scale, shape, and strength of the source. Our results form a baseline for future experimental measurements in intermediate systems.

    hep-phnucl-thPLB(2026)·1 citation
16. 16*

    CNN on `Top': In Search of Scalable & Lightweight Image-based Jet Taggers

    Rajneil Baruah🇮🇳 · Subhadeep Mondal🇮🇳 · Sunando Kumar Patra🇮🇳 · Satyajit Roy🇮🇳

    While Transformer-based and standard Graph Neural Networks (GNNs) have proven to be the best performers in classifying different types of jets, they require substantial computational power. We explore the scope of using a lightweight and scalable version of EfficientNet architecture, along with global features of the jet. The end product is computationally inexpensive but is capable of competitive performance. We showcase the efficacy of our network in tagging top-quark jets in a sea of other light quark and gluon jets. The work also sheds light on the importance of global features for both the accuracy and the apparent redundancy of the network's complexity.

    hep-phphysics.comp-phphysics.data-an0 citations
17. 17*

    Exploring asymmetries in three-body cLFV lepton decays: probing CP violation in HNL extensions of the SM

    Adrian Darricau🇫🇷 · Jonathan Kriewald🇸🇮 · Ana M. Teixeira🇫🇷

    In the context of Standard Model extensions via Majorana sterile fermions, the presence of additional CP violating phases (Dirac and Majorana) has been shown to be at source of important effects in charged lepton flavour violating (cLFV) transitions and decays. Here we will consider further angular observables that can be studied for polarised $\tau$ and $\mu$ cLFV decays. These include, among others, parity asymmetries and time-reversal asymmetries for generic cLFV 3-body decays, ${\ell }_{\alpha }^{+}\to {\ell }_{\beta }^{+}{\ell }_{\gamma }^{+}{\ell }_{\delta }^{-}$. We address relevant correlations between the different classes of observables, and show that one can have sizeable asymmetries, which can be used to further probe this interesting class of SM extensions. Our study leads to the prediction of particular patterns of angular observables, which would allow to potentially falsify the model, should a cLFV signal be observed.

    hep-phJHEP(2026)·1 citation
18. 18*

    Radiative Semileptonic Decays of Beautiful Hadrons

    Federico Cima🇺🇸 · Michele Papucci🇺🇸

    We derive predictions for the hadronic matrix elements of radiative semileptonic decays of beautiful hadrons within Heavy Quark Effective Theory (HQET), relevant for future measurements at Belle II and LHCb. Our study considers Lambda(b) -> Lambda(c), Lambda(*)(c1) and B -> D(*), D** transitions. The symmetries of HQET highly constrain the number of structure-dependent form factors in all cases. In the soft and sub-leading soft regions, all the form factors are fully determined in terms of non-radiative Isgur-Wise functions and the magnetic dipole moments of the heavy hadrons. The structure of higher order corrections is also briefly discussed.

    hep-phhep-exJHEP(2026)·0 citations
19. 19*

    Thermal Damping of Mass-Modulating Scalars

    Abhishek Banerjee🇺🇸 · Ngan H. Nguyen🇺🇸 · Erwin H. Tanin🇺🇸

    The cosmological evolution of a scalar field is shaped by Hubble damping. Any non-gravitational couplings of the scalar with the primordial thermal bath generically contribute additional damping. Although rarely considered, such thermal damping could be the dominant dissipative effect. We derive approximate but highly general thermal-damping rates of scalar fields that modulate the masses of thermally populated particles. We extend previous results to cover cases of particular phenomenological interest where the scalar background oscillates sinusoidally but not necessarily slowly compared to the thermalization rates of the primordial bath. Based on these results, we estimate the thermal damping of scalars coupled to neutrinos linearly, to gluons quadratically, and to WIMPs linearly, and demonstrate its importance in certain parameter space of these models. We also estimate the thermal damping rates in models of QCD axion.

    hep-phastro-ph.COgr-qcPRD(2026)·4 citations
20. 20*

    CoLoRFulNNLO for hadron collisions: regularizing initial-state double real emissions

    Vittorio Del Duca🇮🇹 · Gábor Somogyi🇭🇺 · Francesco Tramontano🇮🇹

    We present the extension of the completely local subtraction scheme CoLoRFulNNLO to color-singlet production in hadron collisions. We provide explicit momentum mappings and the complete set of double-real counterterms required for this class of processes. The counterterms are systematically derived from the known infrared limit formulae of QCD matrix elements, and particular care has been taken to ensure their analytic integrability. The resulting construction involves a relatively small number of counter-events, preserving the locality and efficiency of the scheme. All formulae have been implemented within the publicly available NNLOCAL Monte Carlo program, and we explicitly validate all IR limits using arbitrary-precision computer algebra and present representative results. The counterterms presented here constitute a self-contained subset applicable to general hadronic processes within the CoLoRFulNNLO approach.

    hep-phhep-thJHEP(2026)·8 citations
21. 21*

    Primordial Black Holes from Inflation with a Spectator Field

    Dario L. Lorenzoni🇨🇦 · Sarah R. Geller🇺🇸 · David I. Kaiser🇺🇸 · Evan McDonough🇨🇦

    How is the production of primordial black holes (PBHs) in single-field models of inflation impacted by the presence of additional scalar fields? We consider the effect of a spectator field - a free scalar field with sub-Hubble mass, no direct coupling to the inflaton, and which makes a subdominant contribution to the total energy density - in the context of single-field models of inflation featuring a transient phase of ultra-slow roll (USR) evolution. Despite the modest title, a spectator field can have a dramatic impact: the slow-roll evolution of the spectator prevents the combined inflaton-and-spectator system from entering into USR, which naively might be expected to preclude the production of PBHs. However, we demonstrate that the growth of perturbations is maintained or enhanced by the spectator, through the rich interplay of curvature and isocurvature perturbations. We show in a model-independent way that the single-field phase of ultra-slow-roll is replaced by two turns in field space encompassing a phase of tachyonic instability for the isocurvature perturbations and a transfer of power from isocurvature to curvature modes. Furthermore, we highlight a degeneracy between the fine-tuning of the feature in the inflaton potential and the parameters of the spectator, leading to an overall resilience of model predictions to parameter variations. This makes it easier for the underlying PBH model to accommodate both high-precision CMB constraints and production of PBHs in the asteroid-mass range.

    ↳ astro-ph.COgr-qchep-phhep-th7 citations
22. 22*

    Reanalyzing DESI DR1: 3. Constraints on Inflation from Galaxy Power Spectra & Bispectra

    Anton Chudaykin🇨🇭 · Mikhail M. Ivanov🇺🇸 · Oliver H. E. Philcox🇺🇸

    Models of cosmic inflation generically predict a weak but potentially detectable amount of primordial non-Gaussianity (PNG), which can be used to obtain insights into the degrees of freedom during inflation and their interactions. The simplest types of PNG are the local and non-local (equilateral and orthogonal) shapes of the primordial three-point correlators, which are predicted by models with multiple light fields and derivative interactions in single-field inflation, respectively. In this paper we place constraints on local, equilateral, and orthogonal non-Gaussianities using the power spectrum and bispectrum extracted from first public release of the Dark Energy Spectroscopic Instrument (DESI). Our analysis makes use of higher-order clustering information through a consistent effective field theory (EFT) model for both the power spectrum and bispectrum at one-loop order. Using robust scale cuts where the EFT description is valid, we find the following constraints on PNG amplitudes: $f_{\mathrm{NL}}^{\mathrm{loc}}=-0.1\pm 7.4$, $f_{\mathrm{NL}}^{\mathrm{equil}}=719\pm 390$, $f_{\mathrm{NL}}^{\mathrm{orth}}=-200\pm 100$ (at $68\%$ CL). Non-local PNG constraints can be further improved by combining high-redshift DESI with legacy BOSS data and using simulation-based priors on bias parameters, yielding the strongest large-scale structure constraints to date $f_{\mathrm{NL}}^{\mathrm{equil}}=200\pm 230$, $f_{\mathrm{NL}}^{\mathrm{orth}}=-24\pm 86$. Our constraint on $f_{\mathrm{NL}}^{\mathrm{loc}}$ is competitive with the cosmic microwave background (CMB) limit; the combination gives $f_{\mathrm{NL}}^{\mathrm{loc}}=-0.0\pm 4.1$, $18\%$ stronger than the CMB only result, which represents the strongest bound on multi-field inflation yet obtained.

    ↳ astro-ph.COhep-phhep-thPRD(2026)·39 citations
23. 23*

    Exploring the QCD phase diagram through correlations and fluctuations

    Volker Koch🇺🇸 · Volodymyr Vovchenko🇺🇸

    The exploration of the Quantum Chromodynamics (QCD) phase diagram is a central goal of relativistic heavy-ion collision experiments. This review focuses on the role of fluctuations and correlations as sensitive probes of the phase structure. We discuss theoretical advancements and experimental methodologies employed to map the QCD phase diagram, highlighting constraints derived from both lattice QCD calculations and existing experimental data. Key observables such as cumulants and factorial cumulants of conserved charges (e.g., net-proton, net-charge) are explored as promising signatures of phase transitions and the QCD critical point. We discuss how these quantities are measured experimentally and compared with theoretical predictions, addressing challenges and best practices for meaningful comparisons. Special attention is given to predictions and current experimental results at high baryon density, including recent findings from the STAR collaboration at RHIC. Finally, we identify open issues and future directions for fluctuation and correlation studies at lower collision energies, relevant for future measurements, for example by the CBM experiment.

    ↳ nucl-thhep-phnucl-exEur.Phys.J.ST(2026)·10 citations
24. 24*

    General SIGW source for reheating dynamics

    M. Laine🇨🇭 · S. Procacci🇨🇭

    Working in an arbitrary gauge, we derive the source term for scalar-induced gravitational waves (SIGW) valid during a general reheating epoch. The dominant energy component is allowed to transition smoothly from an inflaton field to a set of fluids, possibly via a period of matter domination. Gauge invariance is verified up to second order.

    ↳ gr-qchep-phJCAP(2026)·2 citations
25. 25*

    Quarkyonic Quark-Meson Coupling Model for Nuclear and Neutron Matter

    Koichi Saito🇯🇵 · Tsuyoshi Miyatsu🇰🇷 · Myung-Ki Cheoun🇰🇷

    We unite the dual quarkyonic model with the quark-meson coupling (QMC) model to construct a novel nuclear model based on the quark degrees of freedom, which can cover a wide range of nuclear densities, from low density to the crossover region. In the model, the relativistic, gaussian quark wavefunction is used to describe the nucleon structure. We first evaluate the energy density, chemical potential, pressure and sound velocity within the ideal Fermi gas picture. In this case, those physical quantities are discontinuous or divergent at the quark saturation density, where the quarkyonic phase emerges. To remove such singular behavior, we next introduce an infrared regulator, and combine the dual quarkyonic model and the QMC model to include the nuclear interaction -- we call it the quarkyonic quark-meson coupling (QQMC) model. In this model, the quark saturation density depends strongly on the nucleon size. For example, when $r_p=0.6(0.8)$ fm, where $r_p$ is the root-mean-square radius of the proton, the quark saturation density is about $3.6(1.5)\times {\rho }_0$ in symmetric nuclear matter, where ${\rho }_0$ is the nuclear saturation density. Furthermore, the nuclear interaction plays an important role in considering physical quantities quantitatively. In fact, the QQMC model can produce the sound velocity which is consistent with that inferred from the observed data of several neutron stars. Furthermore, pressure in symmetric or pure neutron matter deduced from the experiments of heavy-ion collisions at high energy can be explained by the QQMC model as well. We discuss in detail the formulation for the QQMC model and the physical quantities calculated by the model.

    ↳ nucl-thastro-ph.HEhep-ph4 citations
26. 26*

    Constraining regular primordial black holes with isocurvature gravitational waves

    Ngo Phuc Duc Loc🇺🇸

    We find the constraint on the population of ultra-light regular primordial black holes (RPBHs) by using isocurvature gravitational waves (GW). If ultra-light RPBHs dominated the early Universe, the initial isocurvature perturbation is converted into curvature perturbation that induce second-order GW background upon evaporation of RPBHs. The upper limit of extra relativistic degrees of freedom $\Delta N_{\mathrm{eff}}$, which could be inferred from Big Bang Nucleosynthesis or Cosmic Microwave Background observations, places a constraint on the maximum energy density of GW, which in turn can be used to constrain the RPBH population. As RPBHs have different lifetime from their singular counterparts, the constraint must be modified accordingly. While the formalism that we provide is generic, we work out explicitly the case of Simpson-Visser metric for demonstration. The RPBHs associated with this metric have lower Hawking temperature and smaller horizon size, leading to a longer lifetime than the singular Schwarzschild black holes. This implies a stronger constraint on RPBH population as they dominate the Universe for a longer period of time and generate stronger GW.

    ↳ astro-ph.COgr-qchep-phhep-th1 citation
27. 27*

    Thermodynamic and transport properties of hot asymmetric nuclear matter within a chiral SU(3) model

    Amruta Mishra🇮🇳 · J. Schaffner-Bielich🇩🇪

    We investigate the thermodynamic and transport properties in hot nuclear matter accounting for the medium modifications of the nucleons within a chiral SU(3) model including effects from isospin asymmetry. Using the relaxation time approximation, the transport coefficients of the shear viscosity and thermal conductivity are studied. The shear viscosity, $\eta$, calculated within the chiral SU(3) model is observed to be smaller than the values calculated for free nucleon gas, whereas the thermal conductivity $\kappa$ is appreciably larger as compared to the free nucleon gas. The presence of isospin asymmetry in the medium leads to higher values of both the coefficients of shear viscosity ($\eta$) and thermal conductivity ($\kappa$), however, the effect is observed to be marginal for $\eta$. In the chiral SU(3) model, the effect of isospin asymmetry is observed to be larger for higher values of temperature. For T=150 MeV, there is observed to be a drop in the value of $\kappa$ as density is increased, contrary to the increase observed for the lower values of temperature, T=50 and 100 MeV. The shear viscosity coefficient to entropy density ratio $\eta /s$ drops with increasing baryon density that becomes more pronounced at higher temperatures in the chiral SU(3) model as compared to the case of a free nucleon gas. The present study of the thermodynamic as well as transport properties in hot nuclear matter is of relevance for relativistic heavy-ion collisions with different initial isospin asymmetry, in particular for the compressed baryonic matter experiment at the FAIR facility at GSI.

    ↳ nucl-thhep-phPRD(2026)·1 citation
28. 28*

    Constraints on Genesis Cosmology from the Smeared Null Energy Condition

    Dong-Hui Yu🇨🇳 · Mian Zhu🇨🇳 · Yong Cai🇨🇳

    The violation of the null energy condition (NEC) is essential for constructing nonsingular cosmological scenarios, such as Genesis cosmology, which avoids the initial singularity by initiating cosmic evolution from an asymptotically Minkowski state. To address theoretical concerns regarding the accumulation of negative energy, the smeared null energy condition (SNEC) has been proposed as a quantum-motivated, semi-local bound on NEC violation. In this work, we examine the implications of the SNEC conjecture for Genesis models, typically constructed within generalized Galileon theories. Our results demonstrate that SNEC imposes nontrivial restrictions on the viability of Genesis models, highlighting the SNEC conjecture as a powerful tool for constraining nonsingular cosmological scenarios.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2026)·2 citations
29. 29*

    Amortized Inference of Multi-Modal Posteriors using Likelihood-Weighted Normalizing Flows

    Rajneil Baruah🇮🇳

    We present a novel technique for amortized posterior estimation using Normalizing Flows trained with likelihood-weighted importance sampling. This approach allows for the efficient inference of theoretical parameters in high-dimensional inverse problems without the need for posterior training samples. We implement the method on multi-modal benchmark tasks in 2D and 3D to check for the efficacy. A critical observation of our study is the impact of the topology of the base distributions on the modelled posteriors. We find that standard unimodal base distributions fail to capture disconnected support, resulting in spurious probability \textit{bridges} between modes. We demonstrate that initializing the flow with a Gaussian Mixture Model that matches the cardinality of the target modes significantly improves reconstruction fidelity, as measured by some distance and divergence metrics. Finally, we apply this method to a curated problem in heavy flavour physics --- the extraction of the Wolfenstein parameters from the CP asymmetry in $B^0\to J/\psi K^0$; it is multimodal, non-Gaussian, and asymmetric in its mode weights --- and compare the results against a well-converged Markov Chain Monte Carlo reference using different metrics.

    ↳ cs.LGhep-exhep-phphysics.comp-ph+10 citations
30. 30*

    Inflationary relics from an Ultra-Slow-Roll plateau

    Albert Escrivà🇯🇵 · Jaume Garriga🇪🇸 · Shi Pi🇨🇳

    We investigate the formation of primordial black holes (PBHs) in inflationary scenarios featuring an ultra-slow-roll (USR) plateau with a sharp transition to slow roll. We focus on two coexisting production channels: PBHs originating from relic vacuum bubbles where the inflaton got trapped on the plateau, and PBHs arising from standard adiabatic density perturbations. From detailed numerical simulations we find that the bubbles are generically surrounded by type-II curvature fluctuations. Special attention is given to the distribution of initial conditions, including the relevant mean profiles and shape dispersion around them. For the adiabatic channel, we extend the logarithmic template formula $\zeta [{\zeta }_G]$, which maps the Gaussian curvature perturbation to the fully non-Gaussian one while incorporating mode evolution, and we compare this with numerical results obtained using the $\delta N$ formalism. While the template departs from numerical results near its logarithmic divergence, it still provides accurate threshold values for PBH formation in the parameter range relevant to our analysis. Finally, we compute the PBH mass functions for both channels. We find that the adiabatic channel dominates over the bubble-induced channel by a factor $\sim \mathcal{O}(10-10^2)$, and that both contributions are largely dominated by the mean profiles.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2026)·15 citations
31. 31*

    Schwarzschild Black Hole Turbulence: Scalar Probe

    Alex Kehagias🇬🇷 · Antonio Riotto🇨🇭

    We explore how perturbations of a Schwarzschild black hole can redistribute energy among scalar modes and seed turbulent like cascades. We make use of the van der Pol-Krylov-Bogoliubov averaging method and derive coupled mode equations that describe near-resonant interactions between neighbouring multipoles. We compare two routes to instability, namely the difference-frequency mixing between adjacent modes and the diagonal (Mathieu) self-modulation channel. We show that, at high multipole number (eikonal limit), the difference-frequency route dominates and drives a one-way cascade from higher to lower frequencies. We chart the corresponding instability regions ("tongues") and quantify their detuning dependence. The framework provides a simple, quantitative mechanism for energy transfer in black hole ringdowns and clarifies when and how turbulent signatures can arise within linear probes on a weakly perturbed background.

    ↳ gr-qchep-phhep-thJCAP(2026)·4 citations
32. 32*

    Sensitivity of the Hongmeng 21cm experiment to scattering dark matter

    Junsong Cang🇮🇹 · Yu Gao🇨🇳 · Yin-Zhe Ma🇿🇦

    Scattering between dark matter and baryons can cool the intergalactic medium temperature and deepen the 21cm signal. Such interactions have been proposed to explain the unusually deep 21cm absorption signal reported by EDGES in 2018. We explore the potential to detect dark matter - baryon scattering with the Hongmeng project, an upcoming Moon-orbiting satellite experiment dedicated to measuring the global 21cm signal between redshifts $11-46$. We self-consistently forward-model the simulated sky-temperature data, jointly varying the astrophysical and foreground models. We show that even with a very conservative observational strategy in which the experiment only takes data when the Earth and the Sun are both shielded by the Moon, Hongmeng can tighten the current constraints on the cross section of dark matter - baryon scattering ${\sigma }_0$ by a factor of 39 after the full mission, which lasts for five years. The prospective upper limit on ${\sigma }_0$ can reach $5.4\times 10^{-43}\mathrm{c}{\mathrm{m}}^2$ for dark matter masses between 0.1 MeV and 0.3 GeV. Even after only one month of operation, an improvement by a factor of 4 relative to current ${\sigma }_0$ limits can be expected.

    ↳ astro-ph.COhep-ph1 citation
33. 33*

    Evolution of Generic Varying-Tension Cosmic Strings in Expanding Spacetimes

    Hubert Lau Sze Chun🇬🇧 · Joseph Conlon🇬🇧

    It has recently been realised that strings with time-dependent tensions exhibit interesting dynamics; in particular, when the tension decreases loops of string can grow and possibly percolate. We extend previous analytic studies of strings with time-dependent tensions to numerical studies of non-circular loops. We show that the dynamics of a varying-tension string in expanding universe is mathematically equivalent to the evolution of a fixed-tension string in a universe with a modified scale factor. We use numerical solvers and machine learning techniques to explore the dynamics of non-circular string loops with radii close to the Hubble scale.

    ↳ hep-thhep-ph2 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.