Papers

We revisit the evolution of axion domain walls seeded by inflationary fluctuations. In our previous work, we showed that such domain-wall networks retain superhorizon correlations even after entering the scaling regime. We extend our previous analysis to the case with large initial fluctuations, where many minima of the axion potential are already populated when the axion starts to oscillate. Although the conventional misalignment contribution can have suppressed long-wavelength isocurvature perturbations when many vacua are averaged over, axions produced by domain-wall collapse provide an additional contribution that can dominate when the walls enter the scaling regime before annihilation. In particular, the biased vacuum energy released during wall annihilation inherits the superhorizon correlations of the inflationary fluctuations and transfers them to the axion energy density. We find that sizable isocurvature perturbations can therefore survive even after the walls annihilate. We also discuss generic isocurvature constraints on dark matter produced by domain-wall collapse.

Machine learning is now a central tool for solving inverse problems in particle physics and astronomy. Models are trained on simulation and deployed on real data, raising the question not just of whether they fit, but of whether they are wrong in ways we did not anticipate: the unknown unknowns. This challenge of model misspecification is not unique to machine learning. In physics, misspecification is sometimes exactly what we want to find: new discoveries appear as failures of existing models. At other times, we want such effects absorbed into the analysis without biasing the measurement. A robust analysis is one that absorbs the misspecifications we are not interested in, while preserving sensitivity to the ones we are. Machine learning can both amplify misspecification and provide new tools to address it. We discuss the challenges of model misspecification, diagnostics for detecting it, and strategies for mitigation. No single diagnostic can confirm that a model is correctly specified: detection and mitigation are two halves of an iterative loop, in which a battery of complementary diagnostics is applied, the model is updated, and the process repeated. Robustness against unknown unknowns is ultimately less about any single technique than about a disposition: a willingness to suspect one's own model, and to design analyses that can survive being wrong in ways one did not anticipate.

In holography, four-dimensional confining gauge theories are often modelled by five-dimensional Einstein–scalar gravity by choosing a specific form of the scalar potential. In a large class of non-conformal theories, we show that a predictive structure emerges for the thermal confinement transition by generalising the gravitational dual to $D+1$ dimensions and using a $1/D$ expansion. These results are independent of the details of the scalar potential, hinting towards universality. The black brane geometry dual to the deconfined phase can be analytically constructed due to its effects being localised near the horizon at leading order. The solution does not exist below a minimal temperature $T_{\rm min}$ and the maximum possible supercooling in the transition $\epsilon_{\rm sc} = 1-T_{\rm min}/T_{\rm c}$ is generically suppressed by a factor of $1/D^2$. Remarkably, the maximum supercooling at the leading order is set by the speed of sound in the deconfined phase of the gauge theory at the critical temperature, $\epsilon_{\rm sc}=c_s^2(T_{\rm c})/2$. These predictions agree with explicit calculations in an exponential superpotential, improved holography, and the thermal transition in $\mathcal{N}=4$ super Yang–Mills on a sphere.

The nucleon-triggered vector boson $V_{\mathcal B}$ is a hypothetical particle motivated by a statistically significant discrepancy between the KLOE measurement, $\mathrm{BR}^{\eta\rightarrow\pi^{0}\gamma\gamma}_{\text{KLOE}} = \left(0.98\pm0.11_{\text{stat}}\pm0.14_{\text{syst}}\right)\times10^{-4}$, and the current world average, $\left(2.55\pm0.22\right)\times10^{-4}$, dominated by MAMI photoproduction data. This hypothetical new interaction is activated by external nucleons, causing deviations from the Standard Model predictions, while leaving leptonic measurements, such as KLOE and BESIII, unaffected. We embed this mechanism in representative MAMI- and JEF-like photoproduction settings, deriving distinctive and directly testable kinematic and cut-dependent signatures to quantify small differences between the two regimes. One such signature is a small predicted population of events beyond the nominal on-shell boundaries of the $\gamma\gamma$ and $\pi^0\gamma$ spectra, containing 4–23 events in a sample of 1200, depending on the selection window. These events correlate with the recoil proton kinematics, and the polar angle relative to the on-shell hypothesis can reach $\lesssim -5^\circ$ at MAMI energies, but only $\approx -0.2^\circ$ at JEF. For identical selection windows, the JEF-like effective branching fraction exceeds the MAMI-like prediction by less than $1\%$, while widening the window increases both predictions by up to $\sim4\%$. Both energy regimes produce a similar upward shift of the mean reconstructed mass, $\langle M_{\pi^0\gamma\gamma}\rangle-m_\eta\simeq +2$–$7~\mathrm{MeV}$. Finally, we identify representative $V_{\mathcal B}$-induced topologies that could contribute to recently reported discrepancies in the angular distributions of $\gamma d\to\pi^0\eta d$ and $\gamma d\to\pi^0\pi^0 d$, leaving their quantitative investigation to future work.

Hadronic molecules are commonly viewed as products of near-threshold two-body dynamics. We investigate whether an experimentally established molecule can also serve as a building block for a more complex exotic hadron by studying pion scattering off $T^+_{cc}(3875)$. Treating $T_{cc}$ as a correlated isoscalar $D D^*$ molecular cluster, we describe the resulting $\pi D D^*$ dynamics in the $I(J^P)=1(1^-)$ channel within the Fixed Center Approximation to the Faddeev equations. The full three-body amplitude develops a pronounced enhancement slightly above the $\pi T_{cc}$ threshold, centered at $M_{\rm peak}\simeq 4055$~MeV, with an apparent width of approximately $60$~MeV. The associated behavior of the real and imaginary parts of the amplitude is compatible with a resonant-like interpretation. These results show that the lightest hadron can play an active dynamical role in promoting an observed hadronic molecule into a building block of a heavier near-threshold structure generated by the three-body dynamics. We propose searching for this enhancement in the $T_{cc}\pi$ invariant-mass distribution, particularly through the $D^0D^0\pi^+\pi^-$ final state.

Motivated by recent DESI results suggesting dynamical dark energy, we investigate the thawing scenario in quintessence with an exponential potential, $V=V_0e^{-\lambda\phi/m_{\mathrm{pl}}}$, by analytically expanding the deviation of the equation of state parameter $w_{\phi}$ from $-1$ in powers of $\lambda$. In addition to the previously known leading-order result at $O(\lambda^2)$, we derive the $O(\lambda^4)$ correction as a function of the density parameter $\Omega_\phi$. We show that a consistent determination of the redshift dependence of $w_\phi$ through $O(\lambda^4)$ requires corrections to the background expansion. We obtain the required correction by expanding $\Omega_\phi$ in powers of $\lambda$ around its $\Lambda\mathrm{CDM}$ value. Comparison with numerical solutions demonstrates that the $O(\lambda^4)$ expansion provides a more accurate approximation than the leading-order result. Our analytical approximation, which consistently incorporates the $O(\lambda^4)$ correction, will provide a potentially useful tool for distinguishing the exponential quintessence model from other dark energy models in future observations.

We investigate the thermodynamic properties and critical behavior of rotating strongly interacting matter within the two-flavor Nambu–Jona-Lasinio model. The phase structure and critical endpoint (CEP) are determined in the temperature-angular-velocity \((T,\omega)\) plane. Exploiting the thermodynamic conjugacy between the angular velocity \(\omega\) and rotational polarization \(J\), we characterize the CEP through complementary thermal, coexistence, susceptibility, and critical-isotherm responses. The corresponding effective critical exponents are extracted along distinct thermodynamic trajectories and are found to be consistent with \(\alpha_\omega\simeq0\), \(\beta_\omega\simeq1/2\), \(\gamma_\omega\simeq1\), and \(\delta_\omega\simeq3\). These exponents are numerically compatible with the standard scaling relations and form a mutually consistent Landau mean-field scaling pattern. Our results establish a coherent thermodynamic characterization of the rotation-induced CEP and demonstrate how its singular behavior is encoded in rotational response observables associated with the conjugate pair \((\omega,J)\).

Computing neutrino oscillation probabilities is a solved problem; computing their derivatives is not. We present MANGO (MANGO: A Neutrino Gradient Oscillator), a composable oscillation engine in which every computed quantity is differentiable with respect to all inputs, including propagation geometry, detector depth, and individual Earth-shell densities. None of these quantities appear in traditional analytic probability formulas. The engine supports vacuum, constant-density, layered-PREM, arbitrary-profile, and adiabatic solar propagation, alongside front-ends for non-standard interactions, 3+N sterile states, decoherence, and non-unitary mixing. Because reverse-mode cost depends on output rather than input dimension, evaluating sensitivities incurs a constant 2.5-3x forward-pass overhead. As a result, calculating sensitivities for all 369 density, electron-fraction, and shell-radius parameters of a layered Earth costs no more than the 6 standard oscillation parameters. By maintaining exact sensitivity signals, MANGO allows gradients to flow continuously past the probability stage and through detector response, event weighting, binning, and likelihoods. We demonstrate this on a stylized Earth-tomography analysis. In a single pass, MANGO computes the marginalized uncertainty on a six-zone radial density model and, by differentiating through the inverse Fisher matrix, evaluates its sensitivity with respect to detector angular resolution. This provides an experimental-design metric unreachable using traditional analytic probability formulas. Three-flavor and layered-Earth probabilities match external benchmarks (OscProb, NuFast-Earth) to within 10^-9 to 10^-5, while all forward models, BSM limits, and differentiation paths are verified against exact analytic solutions and finite differences.

We study non-perturbative quark-antiquark pair production and the subsequent quark dynamics in the earliest glasma stage of relativistic heavy-ion collisions. For that, we develop a new model, WAGASHI (Wong-precessing Anisotropic Glasma And ScHwinger-produced Initial-conditions), which combines classical Yang-Mills glasma evolution, Wong-equation transport, and Schwinger pair production on an event-by-event basis. We find that a sizeable number of quarks, comparable to the final hadron yields, are produced already during the glasma stage and subsequently undergo substantial momentum broadening and spin randomization, suggesting a significant contribution toward the early equilibration of the quark-gluon plasma. We also determine the event-by-event distributions of baryon number, electric charge, strangeness, and spin polarization in Pb-Pb and O-O collisions at LHC energies, finding particularly large fluctuations in the smaller O-O system. These results provide dynamical initial conditions for the subsequent hydrodynamic evolution of the quark-gluon plasma.

We investigate thermal photon emission from magnetized quark-gluon plasma (QGP) within (1+1)-dimensional relativistic magnetohydrodynamics (MHD), systematically incorporating magnetic susceptibility $\chi_m$—encompassing both constant and lattice-QCD-derived temperature-dependent $\chi_m(T)$ parametrizations—and weak-field quantum corrections to quark distribution functions $f_{\rm EM}$. Employing the Pu-Bjorken MHD framework, we calculate photon production rates from Compton scattering, $q\bar{q}$ annihilation, bremsstrahlung, and annihilation with rescattering, and integrate these over the QGP spacetime evolution to obtain transverse momentum ($p_T$) spectra. Our results demonstrate that photon yields are predominantly governed by the initial magnetic field strength and its temporal decay profile, with $\chi_m$ exerting negligible influence in the explored parameter space. In contrast, the weak-field correction $f_{\rm EM}$ induces a distinct enhancement in thermal photon production at intermediate $p_T$. This work establishes a rigorous theoretical framework for quantifying electromagnetic observables in magnetized QGP and provides the foundation for future dissipative MHD studies incorporating spin-magnetization dynamics.

Recently, it was demonstrated that the disagreement between lattice calculations and holographic models, regarding rotational effects in the quark-gluon plasma (QGP), occurs due to different choices of reference frames. While a static observer measures a confinement temperature that decreases with rotation, one in a co-rotating frame finds the opposite behavior. Both results are correct, and a comprehension of the frame-dependency of the critical temperature is a significant step in the description of the QGP under rotation. In this article, we generalize this previous holographic result by describing the plasma through the most general Myers-Perry black hole solution. This breaks the spherical symmetry present in the equal angular momentum case, considered before. As a consequence, the local temperature measured by a co-rotating observer has a non-trivial angular dependence: it can decrease, increase or even behave non-monotonically when rotational velocity increases.

We develop an efficient three-dimensional numerical-relativity framework for primordial black-hole (PBH) formation from superhorizon curvature perturbations in a radiation-dominated Universe. We implement flux-conservative relativistic hydrodynamics in the adaptive-mesh-refinement code GRChombo and introduce a cosmologically scaled Gamma-driver that allows the cosmic-time step to grow in proportion to the scale factor. For a representative long-term simulation, the scaled driver preserves the apparent-horizon mass evolution and constraint behavior while reducing the number of coarse-level advances by a factor of approximately $94$ relative to the standard driver. We also construct a conformal-time version of the moving-puncture gauge as an independent check. Applying the framework to a spherical Gaussian curvature profile, we find a collapse threshold $0.79578 < \mu_c < 0.79580$ and a critical exponent $\gamma \simeq 0.3559$, consistent with previous spherically symmetric results. We further fit the late-time PBH mass growth to the Zel'dovich–Novikov accretion law, demonstrating that the code can follow both near-critical collapse and long-term post-formation evolution in three dimensions. The framework provides a foundation for future studies of PBH formation beyond spherical symmetry.

In the extended NJL model, the decays of the first radially excited vector mesons $\rho'$,$\omega'$, $\phi'$ and ${K^*}'$ with production of $3P$, where $P=K,\pi,\eta$ are calculated. The box channels and the channels with intermediate vector mesons in the ground and first radially excited states are considered. The obtained results can be considered as predictions for future experiments.

Newtrinos.jl is an open-source Julia package for performing global analyses of neutrino data. It provides a modular, three-layer architecture that separates physics models, experiment descriptions, and statistical inference into independent modules. This allows researchers to freely combine experiments and test them against a variety of theoretical models. New experiments and physics models can be added without modifying core code. Full statistical forward models including all relevant systematic uncertainties are implemented for each experimental dataset, defining both the likelihood and the data-generating process and enabling modern statistical inference workflows. The framework is composable, making it straightforward to construct joint likelihoods over multiple datasets. Physics and nuisance parameters can be merged, correlated, or decorrelated across experiments to ensure consistency in the joint fit. The package supports Frequentist and Bayesian inference and is parallelizable across CPU threads or distributed workers. Written entirely in Julia, all models are automatically differentiable, enabling exact gradient computation.

Introduction of probabilities from multiple inclusive cross-sections is studied in the unitary pomeron exchange models with no interaction between the pomerons themselves. Discrepancy is observed between the emerging inelasic cross-section and the one following from unitarity. It diminishes with energy and disappears in the high-energy limit. Probabilities and entropy are calculated numerically. As a function of energy squared $s$ the entropy grows as \ln\ln s rather than as \ln s, contrary to naive predictions. For the BFKL pomeron the entropy abruptly changes its slope in the rapidity region where consistency of the modelis is approximately restored

We investigate the detectability of high-frequency gravitational waves from the superradiance of light primordial black hole dark matter through photons converted in the Galactic magnetic field. We find that the signal is significantly enhanced in the X-ray frequency range around $10^{18}$Hz. For clustered initial conditions, future X-ray observations may detect the converted photons from primordial black holes in the mass range $10^{-15}M_{\odot} \sim 10^{-13}M_{\odot}$. Our results indicate that future X-ray observations could provide a new probe of light primordial black hole dark matter through high-frequency gravitational waves.

We investigate the impact of an external magnetic field on the in-medium properties of pseudoscalar ($D^0,D^+,D_s$) and vector ($D^{0*},D^{+*},D_{s}^{*}$) mesons in isospin asymmetric nuclear matter at finite temperature using a hybrid theoretical framework combining the chiral SU(3) quark mean-field (CQMF) model and the light-front quark model (LFQM). The medium-modified constituent quark masses, obtained from the CQMF model by including the magnetized Dirac sea contribution and anomalous magnetic moments of nucleons, are used as input to the LFQM calculations of meson masses, weak decay constants, and leading-twist distribution amplitudes. We further incorporate the Landau quantization of the charged mesons restricted to the lowest Landau level, while magnetic field induced pseudoscalar-vector mixing is taken into account for each $D$-$D^{*}$ doublet. We find that the external magnetic field enhances the effective masses and decay constants of both pseudoscalar and vector $D$ mesons by magnetic catalysis, while increasing baryon density generally induces an attractive mass shift and suppresses the decay constant and distribution amplitudes. The Landau level contribution further enhances the effective masses of the charged mesons, whereas the pseudoscalar-vector mixing produces a level repulsion, shifting the vector meson masses upward and the pseudoscalar meson masses downward. The interplay between magnetic field and density effects gives rise to a nontrivial medium behavior of heavy-light meson properties, with isospin asymmetry further inducing a small but systematic mass splitting across all the meson states considered. These results provide useful insights into heavy-flavor dynamics in strongly interacting matter and are relevant to ongoing and future studies at FAIR, NICA, and J-PARC.

The $\Omega^0_c$ baryon is unique among charmed sextet baryons because it decays through the weak interaction. In this work, we investigate the topological amplitudes of $\Omega_c^0$ decays in the $SU(3)_F$ limit. The complete set of tree- and penguin-induced diagrams contributing to $\Omega_c^0$ decays into decuplet and octet baryons is presented. The linear relations between the topological amplitudes and the $SU(3)$ irreducible amplitudes are derived through tensor analysis. Several isospin relations are obtained, and additional relations are derived to test the Körner-Pati-Woo theorem.

In this work, we take a first step to a stochastic real-time description of the vacuum phase transitions in a radiation-dominated FLRW universe from the Schwinger-Keldysh formalism. By splitting the phase transition field $\Phi$ into the long-wavelength mode $\phi$ and the short-wavelength mode $\sigma$ and tracing over the latter as the environment, we obtain a classical Langevin-type equation-of-motion for the long-wavelength field $\phi$, where the quantum effects are encoded in a non-Markov memory kernel and a non-Gaussian noise. As a phenomenological example, we start from a polynomial potential and a thermalized initial state, and study the structure of the memory kernel as well as the correlation functions of the noise term. Further extensions remain possible to describe the whole dynamics of cosmological first-order phase transitions via numerical simulations.

We investigate scalar induced gravitational waves (SIGWs) as probes of a dark QCD crossover. Motivated by twin Higgs and asymmetric twin baryon dark matter scenarios, we consider a dark QCD sector with a confinement scale approximately 5.5 times the Standard Model (SM) QCD scale. We construct the effective energy and entropy degrees of freedom for the SM supplemented by dark QCD sectors containing either three light dark quark flavors or all six dark quark flavors. The resulting equation of state parameter and sound speed are then used to solve the first-order scalar perturbations and the second-order SIGWs through the SM and dark QCD crossover epochs. For a monochromatic primordial curvature power spectrum, we first demonstrate that the realistic SM thermal history modifies the SIGW spectrum relative to the idealized radiation-dominated case. We then show that a dark QCD crossover generates an additional frequency-shifted distortion when the enhanced scalar mode reenters the horizon near the dark confinement scale. This distinctive feature can therefore serve as a characteristic signature of the dark QCD sector. Our results demonstrate that SIGWs provide a complementary cosmological probe of hidden confining sectors, with characteristic spectral features shifted to higher frequencies relative to the SM QCD imprint. The analysis developed in this work can also be extended to other well-motivated theories containing different dark confining sectors.

We propose a modified Polyakov-loop Nambu–Jona-Lasinio (mPNJL) model in which the Polyakov potential is given by an explicit dependence on the quark chemical potential, allowing it to remain finite at zero temperature and thus to describe the confinement-deconfinement transition in cold dense matter. Combining this modified quark sector with hadronic equations of state via a Maxwell construction, we find that, depending on the model parameters, the equation of state can exhibit either two phase transitions, from hadronic matter to confined quark matter and subsequently to deconfined quark matter, or a single transition directly from hadronic to deconfined quark matter or from hadronic to confined quark matter. Stable massive cold hybrid stars with only confined and/or deconfined quark phase are obtained. We systematically examine how the parameters of the modified Polyakov potential and the quark vector interactions control the location of these transitions, and find that repulsive vector interactions are essential to obtain a stable quark core. Hybrid stars with confined and/or a deconfined core can reach maximum masses above $2M_\odot$, provided a sufficiently stiff hadronic equation of state is used at low density. In the core of the maximum-mass configurations, the speed of sound shows variations at finite baryon densities, with c$_s^2(\mu)$ departing from the asymptotic conformal value c$_s^2$ = 1/3 in confined core stars. These variations serve as a diagnostic of the equation-of-state stiffness while remaining fully consistent with causality and thermodynamic stability. This work establishes the qualitative role of each model parameter in shaping hybrid-star structure.

We present the first complete field-theoretic realization of the finite one-loop T4-3-i topology for Majorana neutrino mass. Here, T4-3-i denotes a one-loop realization of the Weinberg operator in which a fermion links the two external lepton–Higgs pairs. If this fermion is a Majorana singlet or triplet, the same interactions generate a tree-level type-I or type-III seesaw contribution, respectively, so that the loop is not the leading source of neutrino mass. This lower-order contribution is removed by taking the mediator to be a Dirac fermion $N$, placing lepton-number violation in a separate Majorana fermion $\psi$ inside the loop, and imposing an exact $Z_2$ symmetry that keeps the new scalars inert and stabilizes the lightest odd state. We classify the allowed electroweak charge assignments and study the minimal singlet-doublet realization, denoted T4-3-i-B1, which contains one Dirac fermion, one Majorana fermion, an inert scalar doublet, and an inert scalar singlet. The resulting rank-two neutrino mass matrix predicts one massless neutrino. We confront both normal and inverted neutrino-mass orderings with neutrino-oscillation and cosmological data, charged-lepton flavor violation, including $\mu-e$ conversion, electroweak precision observables, $h\to\gamma\gamma$, theoretical consistency conditions, the relic abundance, and direct-detection limits. Both fermionic and scalar dark matter are viable. The fermionic candidate has only a loop-induced Higgs coupling and consequently a strongly suppressed spin-independent scattering rate, whereas the scalar candidate couples through a tree-level Higgs portal and can lie above the neutrino floor while remaining compatible with current limits. In both cases, coannihilation with inert scalars is essential for reproducing the observed relic abundance.

We investigate how future high-precision neutron star (NS) radius measurements encode microscopic information about the dense-matter equation of state (EOS), focusing on a possible first-order hadron–quark phase transition and the resulting mass–radius topology. Within a Bayesian framework using meta-model EOSs with nine microscopic parameters, we analyze mock radius measurements $R_{1.4}=11.9\pm\sigma_R$ km with $\sigma_R=0.9$ and $0.1$ km for canonical NSs. We introduce inverse EOS–radius mappings by studying the conditional mean of each EOS parameter as a function of the model-predicted canonical radius $R_{1.4}$. Their slope measures the sensitivity of an EOS parameter to the radius, while their curvature determines the leading precision dependence of its posterior mean through the Jensen expansion. The symmetry-energy parameters $L$ (slope) and $K_{\rm sym}$ (curvature) are strongly encoded in $R_{1.4}$ and their posterior means shift appreciably with improved radius precision, whereas the higher-order hadronic parameters show stronger topology dependence. Among the transition parameters, the transition density $\rho_t$ is the most strongly encoded in $R_{1.4}$, while the energy-density jump and quark-matter sound speed are more strongly associated with the topology of the full mass–radius sequence. Since the different topologies have strongly overlapping $R_{1.4}$ distributions, even precise radius measurements cannot by themselves identify the topology or uniquely determine the high-density transition properties. These results provide a parameter-dependent hierarchy for assessing the scientific return of future high-precision radius measurements and complementary probes of high-density NS EOS.

We calculate soft-gluon corrections for $Z\gamma$ production through next-to-next-to-next-to-leading-order (N$^3$LO) in one-particle-inclusive (1PI) kinematics. We use these results to produce approximate N$^3$LO (aN$^3$LO) QCD predictions for $Z\gamma$ production cross sections in proton-proton collisions at LHC energies. Differential cross sections in photon transverse momentum $p_T^\gamma$ and rapidity $y^\gamma$ are computed at 13 TeV and 13.6 TeV collider energies. Higher-order $K$-factors are examined systematically, and scale and PDF uncertainties are quantified at each perturbative order. Soft-gluon corrections are found to be significant in the high-$p_T$ region, with good perturbative convergence observed at aN$^3$LO.

We propose a low-scale spontaneous leptogenesis scenario within the dynamical minimal scotogenic model for accommodating neutrino masses and inert scalar dark matter simultaneously. Thus, we dub the mechanism Spontaneous Scoto-leptogenesis. In this setup, a rolling Majoron arising from the global $U(1)_{B-L}$ symmetry breaking induces an effective chemical potential for the $B-L$ charge in the presence of $B-L$ violating interactions that allow for the efficient decays and inverse decays of right handed neutrinos (RHN), so it gives rise to the observed baryon asymmetry of the Universe through the electroweak sphaleron conversion. The mechanism becomes effective in the strong washout regime and successfully lowers the viable mass scale of the lightest RHN to the range of TeV scales, thereby making the thermal scotogenic leptogenesis with two hierarchical RHNs accessible to direct tests. We identify the roles of the $\lambda_5$ coupling for spontaneous leptogenesis and inert scalar dark matter through the efficient erasure of the inert scalar asymmetry. We also explore the regime for Majoron dark matter from the kinetic misalignment, showing that a multicomponent dark sector comprising the inert scalar and the Majoron can be realized in the model. The resulting framework provides a unified origin for low-scale baryogenesis, neutrino masses, and multicomponent dark sector, so it can be tested by complementary experimental probes through direct detection experiments, collider searches for inert scalars, and future detection of Majoron dark matter or dark radiation.

We study the possibility of an inverse first-order electroweak phase transition (IFOEWPT) and observable gravitational waves (GW) in a radiative neutrino mass model of scotogenic type where singlet-doublet (SD) fermions, the lightest of whom is the dark matter (DM) candidate, generate the necessary seesaw at one-loop level. Considering the possibility of light neutrinos being Dirac for simplicity and additional detection prospects, we extend the standard model (SM) with two generations of $SU(2)_L$ singlet and doublet fermions, one singlet scalar, and three right-handed neutrinos (RHNs). While RHNs provide the right chiral parts of light Dirac neutrinos, the SD fermions and the scalar singlet facilitate the one-loop neutrino mass diagram. The neutral component of the lighter SD fermion, stabilized under a residual $Z_2$ symmetry plays the role of DM while the heavier SD fermions strongly couple to the Higgs leading to an IFOEWPT where the Universe undergoes two different first-order phase transition as it goes from the symmetric to the final broken Higgs phase. We constrain the parameter space from the requirements of generating the correct neutrino mass, DM relic as well as IFOEWPT while incorporating the existing constraints from different experiments. The final allowed parameter space of the model can be probed at collider, direct-detection, GW and cosmic microwave background (CMB) experiments in near future.

Treating the number of flavors $n$ as a variable in the $O(n)$ model leads to non-perturbative constraints on the spectrum of operators. Using the duality between $O(n)$ and $Sp(-n)$, we extend these relations to negative even values of $n$ and we make them explicit by decomposing operators with general flavor structure into irreducible representations. In perturbation theory, we exploit this structure to reveal novel degeneracies in the scaling dimensions of different operators, which persist for arbitrary $n$. This allows us to derive the two-loop anomalous dimension of any $\phi^k$-type operator from existing results without additional loop calculations. The same mechanism dictates patterns in renormalization group mixing matrices, yielding new non-renormalization results in a specific operator basis. We comment on extending this framework to relations between operator product expansion coefficients and to analogous constraints arising from evanescence under continuation in the number of spacetime dimensions.

The Singlet-Doublet fermion model of dark matter is an economical weak-scale dark matter model that realizes the dark matter abundance through interactions with the electroweak bosons of the Standard Model. Depending on the size of the Yukawa couplings in the model, the dark matter relic abundance can be produced via freeze-out (including co-annihilation), co-scattering, freeze-in, or the SuperWIMP mechanism. We analyze the ways this model can realize the dark matter density with emphasis on the small Yukawa coupling regime. In this limit, direct and indirect detection are difficult, but a rich collider phenomenology is possible.

We study decay of a scalar field false vacuum near a (3+1)-dimensional Schwarzschild black hole equilibrated at Hawking temperature with the environment. Our scalar field model has negative quartic self-coupling and thereby resembles Higgs sector of the Standard Model in the large-field limit. We demonstrate that if the black hole is not too small, the false vacuum in this model decays aspherically with regard to the black hole center: via formation of expanding true vacuum bubbles emerging on the outer side of the event horizon. More specifically, we identify three regimes of the decay. For the largest and coldest black holes, the main mechanism is quantum tunneling described by an infinitesimally thin bounce sitting at some point of the horizon. In the intermediate-mass regime, the vacuum is destroyed by thermal fluctuations creating aspherical critical bubbles in the horizon vicinity. Finally, near the smallest black holes thermal fluctuations still guide the decay but the dominant critical bubble is spherically symmetric and covers the entire horizon.

We propose a new mechanism for dark matter genesis, Defect-Mediated Conversion (DMC). Cosmological domain walls can host a scalar condensate in their core acting as a mixing portal between the Standard Model and a dark sector: thermal-bath fermions crossing the wall are partially and non-thermally converted into dark particles. The conversion probability is governed by a single dimensionless mixing area built from the wall profile, and the yield by the area density of the network. For a light dark particle the probability is independent of both the incident energy and the dark mass, and the relic abundance collapses onto a single mass–coupling relation running from the keV Lyman-$\alpha$ floor to the wall-formation scale. For a heavy one, conversion turns the energy of a single incident fermion into the dark mass, populating dark sectors with masses exceeding both the bath temperature and the mediator mass. The same portal also sources ordinary freeze-in, but DMC, boosted by the coherent wall-area enhancement, dominates it by one to two orders of magnitude at fixed couplings and remains operative in the heavy regime, where freeze-in shuts off.