Papers

I present new results for the massive cusp anomalous dimension at four loops in QCD. I combine partial exact and conjectured analytical expressions with an approximation that is based on the asymptotic behavior of the cusp anomalous dimension to produce the newest estimates. Detailed comparisons are made with previous approximate results that highlight the robustness of the calculational approach.

In this work, we study the noisy truncated Hausdorff moment problem in the context of recovering parton distribution functions (PDFs) from their moments. We start by reviewing basics of the Hausdorff moment problem and analyze how the relation between the amount of moment data provided and the ability for $f(x)$ to be reconstructed varies across different classes of parton distribution functions; we then turn to using Bayesian methods centered around Gaussian Processes (GPs) to solve the moment problems. Standard aspects of Bayesian regression such as covariance kernel choice, analytical characterization of the posterior, hyperparameter sampling with Monte Carlo methods, and validation metrics are detailed. In addition to this, powerful novel tools, such as a method to correct for mean bias in posterior distributions, and a simple class of covariance kernels whose $x$ correlation length is learned during sampling are introduced. Finally, we test our framework on 5 datasets from valence, gluon, and sea quark phenomenological pion and nucleon PDF datasets, selected to reflect diversity in PDF behavior. We find that our GP framework robustly reconstructs PDFs given a moderate number of moments. Additionally, the novel tools developed in this work resolve persistent issues that would be difficult to address via conventional means. The presented framework can be readily applied to moments obtained via lattice Quantum Chromodynamics (LQCD) to reconstruct PDFs from theoretical first principles.

The recent observation of an isolated nuclear recoil event at an energy of $248\pm 23 (stat)\pm 23 (sys)$ keV, as reported by the LUX-ZEPLIN (LZ) collaboration, can be an intriguing signature for Beyond the Standard Model (BSM) possibilities, particularly for dark matter (DM). This paper explores a scenario in which the observed recoil could simultaneously signal inelastic DM and a flavor-specific New Physics (NP) interaction in the quark sector. Considering a minimal extension of the Standard Model (SM) with two closely degenerate $Z_2$-odd vector-like fermions (VLFs), interacting with the SM via a scalar portal, the analysis shows that a perfect agreement with the observed 248 keV nuclear recoil can be achieved if the quark Yukawa couplings are allowed to deviate from their SM values. The underlying quarkophilic NP can originate from a dimension-6 effective operator at a NP scale $\Lambda\leq \mathcal{O}(10)$ TeV. Future collider searches can be crucial to test/falsify the proposal.

The penguin-dominated $B\to\phi K$ decays provide sensitive probes of physics beyond the Standard Model. Interpreting them at increasing experimental precision requires control of doubly Cabibbo-suppressed hadronic contributions. Using a factorization approach, we obtain Standard Model benchmarks for the branching ratios and CP-violating observables, including the hadronic phase shift in $B_d^0\to\phi K_{\rm S}$. The $B_s^0\to\phi K_{\rm S}$ channel, in which the corresponding penguin effects are not Cabibbo-suppressed, offers additional insight into these contributions. Comparing the neutral and charged $B\to\phi K$ modes further allows the construction of isospin observables. We discuss their Standard-Model expectations and sensitivity to New Physics in the $I=0$ and $I=1$ sectors. The available data are consistent with the Standard Model, while leaving substantial room for New Physics contributions.

We present the first study of shear viscosity induced cavitation incorporating transverse expansion alongside chemical non-equilibrium dynamics in the Quark-Gluon Plasma (QGP). Chemical non-equilibrium is incorporated through quark and gluon fugacities, whose evolution is coupled to causal dissipative relativistic hydrodynamics in the Gubser geometry. Using phenomenological temperature-dependent shear viscosity parametrizations, we study the evolution of the longitudinal pressure and identify the conditions under which it becomes negative and thereby breaking down the hydrodynamic description. We demonstrate that shear induced cavitation develops first at the centre of the fireball ($r=0$) at early times and subsequently extends towards larger radial distances, with transverse expansion accelerating its onset, while persisting during chemical equilibration. Within our framework, we determine the critical initial shear viscosity $(\eta/s)_{\rm crit}$, below which cavitation does not occur throughout the QGP evolution. Since hydrodynamics is found to successfully describe the phenomenology of heavy-ion collisions, our results provide a constraint on shear viscosity requiring the absence of cavitation during the QGP evolution. We find that the phenomenologically extracted $\eta/s$ from JETSCAPE analyses lie below the critical shear viscosity $(\eta/s)_{\rm crit}$ obtained in our framework.

We discuss the pion gravitational form factors at intermediate and large spacelike momentum transfer in a perturbative-QCD factorization framework. The short-distance kernel is supplemented by the one-loop non-Abelian $TJJ$ correlator, where the energy–momentum tensor couples to two off-shell gluons. Its trace sector contains the QCD conformal anomaly and admits a scalar, dilaton-like pole interpretation. A transverse-momentum-dependent pion wave function, combined with Sudakov resummation and a Gaussian intrinsic-transverse-momentum profile, suppresses endpoints and large transverse separations. The projection on the pion form factors exhibits a characteristic hierarchy: the isolated anomaly cancels in the momentum form factor 4A_\pi$, remains important in the mechanical form factor $D_\pi$, and dominates the $TJJ$ correction to the trace form factor. The result identifies a beta-function-controlled short-distance contribution to pion mechanical structure and clarifies the relation between the perturbative anomaly pole and a correlated scalar partonic channel.

We develop an operator-level framework for reconstructing the angular structure of small-$x$ diffractive amplitudes from energy-flow measurements. Focusing on coherent diffractive dijet production in the leading-eikonal approximation, we establish the relation between the angular multipoles of the dipole amplitude, the gluon Wigner distribution, and the diffractive scattering amplitude, while keeping their distinct radial transforms explicit. We show that, in the real common-phase sector and away from diffractive zeros, the normalized scattering amplitude can be reconstructed directly, up to a global sign convention, from the square root of the normalized energy-flow distribution. For generic complex amplitudes, the measured intensity instead determines autocorrelations of the amplitude spectrum and phase retrieval is not unique without additional information. We further discuss corrections arising from harmonic-dependent phases, practical conditions for an EIC extraction, and effects beyond the leading-eikonal approximation.

A detailed collider study of Higgs production in the process $e^+e^- \to ZH$ is presented within the framework of the Two-Higgs-Doublet Model (2HDM), with particular emphasis on mis-aligned scenarios in the Type-I realization. The analysis is performed at a future $e^+e^-$ collider with $\sqrt{s}=500$~GeV and an integrated luminosity of $10~\mathrm{ab}^{-1}$, considering heavy Higgs masses in the range $160 \leq m_H \leq 400$~GeV. The analysis covers heavy CP-even Higgs states with non-fermionic decay modes such as $H\to WW$ and $H\to hh$, and incorporates final states arising from leptonic and invisible $Z$ boson decays. Fast parametrized detector-level simulations are employed to evaluate selection efficiencies, signal–background discrimination, and exclusion sensitivities. It is shown that values of $|c_{\beta-\alpha}|>0.1$ can be excluded at the $95\%$ confidence level over almost the entire range $1\leq\tan\beta\leq10$ in the $H\to WW$ scenario, while the $H\to hh$ channel provides lower sensitivity.

White dwarfs (WDs) are compact remnants of stars, supported by electron degeneracy pressure, and their structures are generally considered to be well understood. Significant discrepancies exist between the theoretical and observed white dwarf mass-radius (MR) relations, especially for hot Q-branch white dwarfs with unexplained heating sources. In this study, we explore the potential of WDs as a portal to dark matter (DM) physics by investigating the effect of self-annihilating DM (SADM) admixed in WDs, solving the set of two-fluid hydrostatic equilibrium and heat diffusion equations self-consistently. We obtain empirical formulae for the WD luminosity $L$ and effective temperature $T_\text{eff}$ as functions of the DM mass fraction $f_d$, annihilation cross section $\langle\sigma v\rangle$, and particle mass $m_\chi$, as well as the WD's total mass $M_t$. We also compare the WD MR relations for various $L$, $f_d$, and both Fermionic and Bosonic DM particle statistics, with the observational data. We show that the majority of observed deviations in the WD MR relation can be accounted for by having SADM admixed with $f_d \le 10^{-5}$ and $\langle\sigma v\rangle \ll 3\times10^{-26}$ $\text{cm}^3$ $\text{s}^{-1}$, the thermal relic cross section. Therefore, our results suggest that WDs can be sensitive DM detectors, and DM self-annihilation could provide additional heating in WDs, accounting for their observed extra luminosities.

We construct the Yukawa couplings of the quark sector as overlap integrals of Gaussian wave functions in extra spatial dimensions. Assuming that the wave function of each chiral fermion is localised at a point in the extra dimensions, while that of the Higgs doublet is flat, the Yukawa matrix elements are determined by the relative positions of the three left-handed quark doublets, $q_1$, $q_2$, $q_3$, and the six right-handed quark singlets, $u_1$, $u_2$, $u_3$, $d_1$, $d_2$, $d_3$. We employ numerical optimisation techniques from machine learning to identify field configurations that satisfy all current experimental constraints on the quark Yukawa sector. In this framework, the large hierarchy of quark masses arises naturally, since the overlap integrals of Gaussian wave functions are exponentially sensitive to ${\mathcal O}(1)$ separations in the extra dimensions.

During a core-collapse supernova (CCSN), the emitted electron antineutrino ($\bar{\nu}_e$) burst initiates inverse beta decay (IBD) in the outer hydrogen layer of the stellar envelope. This leads to the production of a characteristic 511 keV photon signal, termed the Gamma-Ray Echo. The same neutrino burst, when detected on Earth in large neutrino observatories such as Hyper-Kamiokande, will offer information about the $\bar{\nu}_e$ content of the neutrino flux reaching Earth. In this work, we show that comparing the $\bar{\nu}_e$ content inferred from the gamma-ray echo with that inferred from terrestrial neutrino observations during a nearby CCSN event can offer a promising probe of large neutrino emission anisotropies and long-baseline propagation effects. In the latter case, the combined SN-Earth observations effectively act as a near-far detector configuration for neutrino propagation over an astrophysical baseline. We find that, for a near-Earth supernova, anisotropies or non-standard propagation effects at the level of tens of percent can be tested using gamma-ray telescopes with effective areas of $\mathcal{O}(10^4)~\mathrm{ cm^2}$. Therefore, our results motivate the development of the next generation of large effective area gamma-ray telescopes operating in the MeV gap.

We study a five-dimensional realization of endothermic dark matter motivated by the recent high-recoil LUX-ZEPLIN event. A pseudo-Dirac Standard-Model singlet fermion is localized in the extra dimension and couples to a bulk $U(1)_D$ gauge field. The same localization that suppresses a distant-brane Majorana operator and generates the inelastic splitting also controls the couplings to the Kaluza–Klein (KK) dark-photon tower, producing a localization-filtered mediator propagator. We organize the phenomenology around two representative mass–splitting points: an LZ benchmark, $m_\chi=1.10~\TeV$ and $\delta=365~\keV$, and an IceCube-motivated comparison point, $m_\chi=1.08~\TeV$ and $\delta=566~\keV$. The latter is used only to compare terrestrial and solar kinematics; the published IceCube bound is Higgsino-specific and is not directly imposed on our singlet KK model. At the LZ benchmark with $R^{-1}=0.30~\GeV$ and $m_0=0.10~\GeV$, the KK tower enhances the high-recoil xenon rate by a factor of about four relative to a single dark photon at fixed microscopic coupling. The LZ point lies just below the terrestrial halo speed ceiling, whereas the $566~\keV$ comparison point is inaccessible to ordinary xenon scattering and instead lies in a kinematic regime accessible to solar capture; any neutrino constraint on the present singlet model remains dependent on its capture and annihilation dynamics. The characteristic prediction of the extra-dimensional construction is therefore a correlated interplay of localization, KK spectral distortion, and inelastic kinematics.

The axion-photon coupling, crucial for experimental axion searches and tests of the strong CP solution, receives a substantial model-independent contribution $\mathcal C_{\rm QCD}$ from QCD dynamics. Next-to-leading-order chiral perturbation theory (NLO ChPT) in different frameworks has yielded puzzling discrepancies of up to $8\%$, motivating precise first-principles calculations. We present an independent lattice QCD determination using a method complementary to the recent background-field calculation. Computing pseudoscalar-to-two-photon three-point functions and exploiting anomalous Ward identities, we separate $\mathcal C_{\rm QCD}$ into an exact anomaly contribution and a light-quark-mass-suppressed correction. The latter is computed using domain-wall fermions, whose excellent chiral symmetry strongly suppresses discretization effects. Working on two near-physical $N_f=2+1$ ensembles with continuum extrapolation, we obtain $\mathcal C_{\rm QCD}^{\rm IS}=1.619(30)$ (isospin-symmetric), $\mathcal C_{\rm QCD}^{\rm IB}=0.347(22)$ (isospin-breaking), and $\mathcal C_{\rm QCD}=1.965(35)$ in total. While direct comparisons with published NLO ChPT predictions reveal apparent tensions, we identify their sources and show that the ChPT results can be reconciled with our lattice determination. Our result provides a first-principles benchmark for the QCD contribution to the axion-photon coupling and a quantitative test of competing ChPT descriptions.

Quantum tunnelling plays a central role in the structure and spectroscopy of hydrogen-bonded systems, and its sensitivity to isotopic substitution provides a stringent probe of the underlying potential-energy landscape. Despite extensive numerical studies, many high-level approaches tend to obscure the simple physical relationships linking effective mass, barrier geometry, and tunnelling amplitudes. Here, we develop a Cornell-type analytical–numerical framework to describe proton and deuteron tunnelling, combining a semi-analytical localized wavefunction ansatz with numerical solutions of the one-dimensional Schrödinger equation. The resulting tunnelling splittings exhibit an exponential dependence on the square root of the effective isotope mass,$\ln(\Delta E)\propto -\sqrt{\mu_{\mathrm{eff}}}$, in agreement with semiclassical Wentzel–Kramers–Brillouin (WKB) theory. Comparison with multidimensional reaction-space calculations for the formic acid dimer shows that this scaling persists in fully coupled 3D and 5D quantum models, yielding an empirical relation $\ln(\Delta E)= -1.75\sqrt{\mu_{\mathrm{eff}}}+2.60$. The present framework provides a transparent and computationally efficient approach for quantifying mass-scaling and tunnelling dynamics in hydrogen-bonded and other double-well systems.

Black holes ring when perturbed, whereas their response to a stationary gravitational-wave background is a real-frequency scattering problem, not a source of additional quasi-normal-mode lines. We make this standard distinction quantitative by treating a black hole as a frequency-, angle-, and polarization-dependent filter. For an isotropic stationary background around Schwarzschild holes, elastic scattering produces no net monopole signal, so horizon absorption is the only population-level spectral distortion. We calculate this transfer function for Schwarzschild holes in detail, identify its absorptive and phase-delay signatures, and connect the stationary response to the causal ringdown excited by a finite wave packet. We then promote the single-hole result to an angular and polarization transport kernel for a cosmological population. The resulting optical depth is negligible for realistic black-hole populations, including asteroid-mass primordial black holes comprising all dark matter. We then extend the analysis to Kerr holes, for which superradiance allows genuine amplification in selected co-rotating modes, but isotropic incidence and random spin orientations strongly dilute the diffuse signal. Observable effects are therefore more likely in rare, nearby, aligned, rapidly spinning, or transiently illuminated systems than through cumulative cosmological propagation.

Light, weakly coupled particles can be copiously produced in the hot and dense interior of stars, and the resulting energy loss can leave observable imprints on entire stellar populations. For instance, additional energy loss from red giant cores delays helium ignition and brightens the tip of the red giant branch (TRGB). We revisit the TRGB bounds on light scalars coupled to electrons, of which the Higgs portal is the prototypical example. In the degenerate cores of red giants, scalar emission is dominated by resonant conversion of longitudinal plasmons, which we compute using finite-temperature field theory. Rather than rescaling neutrino emission rates at fixed benchmark core conditions, we implement this emissivity in the MESA stellar evolution code and self-consistently simulate the evolution of red giants, including the backreaction of the scalar energy loss on the stellar structure. Comparing our predictions with the observed bolometric TRGB magnitudes of 27 Milky Way globular clusters, we exclude scalar-electron couplings $\alpha_{\phi ee} = g_e^2/4\pi > 1.6 \times 10^{-34}$ at 95% confidence for sub-keV masses, improving on previous bounds by nearly two orders of magnitude. In the context of the Higgs portal, this corresponds to an exclusion on values of the mixing angle $\sin\theta > 2.2\times 10^{-11}$, providing the tightest bound for scalar masses in the $\sim 1\,\mathrm{eV} - 10\,\mathrm{keV}$ range.

We investigate constraints on additional relativistic species and thermal sterile neutrinos using the DESI DR1 one-dimensional Lyman-$\alpha$ forest power spectrum, combined with Planck 2018 CMB and DESI DR2 BAO measurements. We consider both the $\Lambda$CDM+$N_{\rm eff}$ extension and a thermal with a different-temperature sterile-neutrino (DTS) scenario, in which the sterile relic can be colder than the standard neutrino background. We first validate the DESI two-parameter $P_{\rm 1D}$ compression for the DTS model, finding that the residual cosmological dependence not captured by the compressed parameters remains below 0.15%. No significant evidence for additional radiation or a sterile component is found. For $\Lambda$CDM+$N_{\rm eff}$, we obtain $N_{\rm eff}<3.41$ at 95% credibility from CMB+DESI-BAO+DESI-$P_{\rm 1D}$. In the DTS scenario, the full CMB+DESI-BAO+DESI-$P_{\rm 1D}$ combination yields the stringent bound $m_s^{\rm eff}<0.061\,{\rm eV}$, highlighting the complementarity of BAO and Lyman-$\alpha$ information in constraining the massive sterile abundance. We further interpret the allowed $\Delta N_{\rm eff}$ in terms of thermal light relics, deriving lower limits on their decoupling temperatures that reach the QCD epoch.

Axion-like particles (ALPs) with masses between 10 MeV and 10 GeV and moderately small couplings sit in an experimental blind spot. They decay too fast for intensity-frontier experiments and are too feebly coupled and too light for conventional collider searches. The LHC produces them at substantial rates through vector boson fusion (VBF), the dominant production mode for electromagnetically coupled ALPs, but two obstacles keep this signal out of reach. The events are soft, so trigger thresholds discard most of them, and the Lorentz boost merges the two decay photons into a single calorimeter deposit. We show that the Compact Muon Solenoid (CMS) experiment can overcome both by combining its data-acquisition strategies with the tracker-based reconstruction of merged photon pairs. Data parking on the VBF jet topology in Run 3 (312 fb$^{-1}$) and trigger-level data scouting at the High-Luminosity LHC (HL-LHC, 3 ab$^{-1}$) remove the need for a threshold on the photons. Photons that convert to electron-positron pairs in the silicon tracker resolve the merged pair, since the tracker measures their direction far more finely than the calorimeter granularity. Reconstructing the ALP decay vertex from the conversion tracks removes the prompt backgrounds but not the long-lived $K_L\to\gamma\gamma$. In Run 3, where the full event is recorded, the merged diphoton invariant mass confines the $K_L$ to a narrow window around its own mass. In the scouting stream, where only trigger-level information survives, the diphoton $p_T$, the conversion tracks, and the hadronic activity in the event take over this role. We project that the parked Run 3 data, already recorded, reach a region of the $(m_a, g_{a\gamma\gamma})$ plane that no measurement has probed. Level-1 trigger data scouting at the HL-LHC extends that reach by roughly an order of magnitude in both coupling and mass.

We initiate a systematic cosmological investigation of an axio-dilaton system governed by a curved field-space metric as generically motivated by supergravity and string compactifications. The scalar sector consists of a light scalar dilaton field evolving along an asymptotically exponential potential and a pseudoscalar field spanning an essentially flat direction, kinetically coupled through an exponential field-space metric. Deviations from the asymptotic regime are incorporated by introducing a generalised Albrecht-Skordis potential containing a polynomial factor. Utilising a dynamical systems approach alongside numerical evolution and Bayesian inference, we constrain the model using Type Ia Supernovae (SNe Ia), Baryon Acoustic Oscillations (BAO) and Planck 2018 distance-prior data. We identify a parameter degeneracy indicating that steeper potentials demand stronger field-space kinetic couplings to sustain late-time cosmic acceleration. Finally, a joint likelihood analysis reveals that while the model successfully accounts for dark energy dynamics, it is only slightly statistically favoured over $\Lambda$CDM by current observations.

The lifetime of the strong magnetic field generated in relativistic heavy-ion collisions remains one of the major open questions in the study of the quark–gluon plasma. We propose heavy-quark spin precession as a probe to quantify the magnetic field and its profile in such collisions. We investigate the Larmor evolution of polarized charm and bottom quarks propagating through an expanding quark–gluon plasma in the presence of the magnetic field. We show that realistic magnetic-field strengths and lifetimes generate measurable accumulated precession phases prior to hadronization, leading to characteristic charge-dependent polarization splittings between $\Lambda_c^+$ and $\bar{\Lambda}_c^-$, as well as between $\Lambda_b^0$ and $\bar{\Lambda}_b^0$, through the mixing of transverse and longitudinal polarization components. The predicted signals exhibit distinctive transverse-momentum and quark-mass dependence, providing complementary sensitivity to the magnetic-field lifetime in the charm and bottom sectors. Our results suggest heavy-flavor polarization, especially in the charm sector, as a quantitative probe for the space–time evolution of magnetic fields in relativistic heavy-ion collisions.

We investigate whether adding $t$, the positive magnitude of the squared nuclear four-momentum transfer, enables boosted decision trees (BDTs) to improve invisible-dark-boson selection relative to optimized rectangular cuts at the Electron-Ion Collider. We model coherent exclusive scalar and vector production at generator level in electron-gold collisions at 18 GeV by 100 GeV per nucleon. Both methods use identical weighted samples, inputs, preselection, and optimization objectives. Using only electron information, the BDT provided no consistent advantage over optimized cuts for signal selection across 11 masses for each boson type. When both methods also use $t$, the BDT distinguishes signal from background slightly better than optimized cuts at 10 GeV for both boson types. These results motivate further investigation of machine learning in EIC dark-boson searches through exclusive processes where $t$ can be reconstructed.

We present a nonparametric determination of spatial curvature using only late-time geometrical probes. Under a Gaussian Process smoothness prior, we jointly constrain the dimensionless expansion history and $\Omega_K$, combining three Type Ia Supernovae (SNeIa) samples with either DESI DR2 line-of-sight baryon acoustic oscillations (BAO) or cosmic chronometers (CC) data. From our baseline SNeIa+BAO analyses we find $\Omega_K=0.219^{+0.110}_{-0.111}$, $\Omega_K=0.330^{+0.098}_{-0.150}$ and $\Omega_K=0.260^{+0.124}_{-0.127}$ for the PantheonPlus, DES Dovekie and Union3 SNeIa samples respectively. These nonparametric results mildly favour an open Universe, supporting recent hints in this direction, and improve on the sensitivity of a previous application of the method by up to a factor of $\sim 2.5$. We find consistent constraints combining SNeIa and CC, whereas restricting SNeIa data to the redshift range covered by BAO somewhat weakens the constraints and shifts the PantheonPlus central value to $\Omega_K<0$. Our results depend only on late-time relative distances and expansion rates, making them insensitive to the absolute distance scale calibration, while relying neither on Cosmic Microwave Background data nor on a parametric dark energy model.

Statistical evidence for a continuous hadron-quark transition is found in this work. Confronting microscopic descriptions connecting the Parity Doublet Model and the Nambu–Jona-Lasinio model with observationally constrained non-parametric equations of state, Bayesian model comparison decisively favors a boundary-free crossover over the conventional first-order Maxwell construction ($\Delta\ln\mathcal{Z} \sim +7.20$) and fixed-boundary crossover ($\Delta\ln\mathcal{Z} \sim +5.16 $). The preferred crossover decouples the intermediate stiffening from the intrinsic stiffness of each phase, allowing both sectors to exhibit physical self-consistency. The chiral-invariant nucleon mass is large, $M_0 = 834^{+28}_{-92}\text{ MeV}$, as expected for a substantial baryon mass surviving chiral restoration. While the quark sector accommodates a small pairing gap $\Delta_{\rm CFL} = 88^{+83}_{-59}\text{ MeV}$ consistent with perturbative QCD limits, avoiding the excessively large gaps $\Delta_{\rm CFL} \gtrsim 200\text{ MeV}$ required by the other constructions. These results demonstrate that a realistic unified description represents a continuous transition deviating substantially from isolated effective models of hadrons and quarks. Exploring genuine phase boundaries is therefore necessary through the emergence of spinodal instabilities within unified frameworks.

Non-thermal cosmological histories rest on the assumption that scalars displaced during inflation undergo coherent oscillations, dominate the energy density of the universe before Big Bang Nucleosynthesis, and decay perturbatively through gravitationally suppressed interactions. In addition, usually a single dark matter component is assumed. This early matter-dominated era is the basis for the usual predictions of non-thermal WIMP production, axion dark matter, entropy generation, and dark radiation. This paper examines whether this picture is dynamically robust against non-perturbative decay of the modulus condensate. In this work, we study non-perturbative particle production from oscillating moduli using the effective field theory appropriate to $G_2$ compactifications. We find that non-perturbative production of Wino-like fermions is strongly suppressed in the relevant parameter regime. In contrast, a modulus-dependent axion kinetic term admits narrow instability bands with growth rates that can exceed the Hubble rate. A linear Floquet analysis alone, however, cannot determine whether these bands significantly deplete the modulus condensate, since cosmic expansion, backreaction, rescattering, and higher-order operators in the effective theory can become important. As a result, the conventional modulus-dominated cosmology remains robust against Wino and gauge-field preheating, while the axion channel provides a potentially important modification that requires nonlinear study. If sufficiently efficient, axion production can alter the division of dark matter between Winos and axions and enhance the dark-radiation abundance.

We compute the gravitational wave spectrum produced by a global cosmic string network in the scaling regime. The spectrum naturally divides at the string correlation length into infrared and ultraviolet parts. In the infrared, we derive the spectrum analytically from the unequal-time correlator of the string stress-energy tensor within the unconnected segment model, which we generalize for the first time to string loops. The loop contribution can be comparable to that of long strings, depending on the loop evolution parameters. In the ultraviolet, where structure below the correlation length dominates the source, we develop a data-driven method that connects this correlator formalism to the instantaneous radiation power spectrum measured in existing lattice simulations. The predicted spectrum rises with frequency as $\Omega_{\rm GW}\propto k$ and $k^{3}$ in the infrared, and flattens into a plateau with a mild logarithmic tilt in the ultraviolet. The turnover frequency between the two is set by the mass of the Goldstone boson, the axion. Confronting the predicted spectrum with current data and projected sensitivities, we map out current constraints and future probes in the plane of the symmetry-breaking scale~$f_a$ and the axion mass~$m_a$.

Vector fields with a chiral, parity-odd coupling to a pseudoscalar field are known to undergo resonant amplification. In this work, we study this phenomenon in the context of cosmological gravitational particle production during early-universe inflation. We consider a massive vector (dark photon) field with a parity-odd coupling to the inflaton. There are two regimes of production, delineated by the relative size of the coupling and the dark photon mass, arising from a tachyonic instability, and a parametric resonance, respectively. As a result of the coupling, the transverse modes, subdominant in both the minimally and nonminimally coupled theories, can dominate the total late-time abundance. The viable parameter space for dark-photon dark matter is thus widened. Furthermore, in the tachyonic case, the production is dominated by a single helicity mode, leading to a population of chiral dark photons that can lead to potential parity-violating observational signatures. We further explore the dependence of the production on the reheating history, and find that information about reheating is encoded in the number density spectrum.

Coherent hard exclusive reactions on light nuclei offer access to their quark and gluon structure and provide a framework for three-dimensional nuclear tomography. We analyze deeply virtual Compton scattering on a helium-4 target, including leading-twist contributions as well as kinematical twist-3 and twist-4 effects. We present numerical estimates of cross sections and asymmetries for kinematic regimes relevant to JLab experiments. We emphasize the importance of next to leading order (NLO) and kinematical twist 3 and 4 contributions to interpret data in the JLab kinematics. We deduce a first tomographic image of quarks and gluons in the helium-4 nucleus.

The text analyzes the concept of mass within Special Relativity, initially deconstructing the interpretation of Einstein's equation ($\varepsilon_\circ = m c^2$) as a principle of equivalence. Based on the adoption of the conservation laws of momentum and energy, the non-additivity of mass in composite systems is established. While in atomic and nuclear systems the total mass is less than the sum of its constituents, in the subnuclear domain the opposite occurs: the positive potential energy of confinement of quarks causes the mass of a hadron to be greater than the sum of the masses of its quarks; in the case of nucleons, it is much greater. It is concluded, then, that the mass of baryonic matter in the observable Universe comes, for the most part, from the energy associated with strong interactions.

The recent observation of the high-energy nuclear recoil event LZ230616 with a recoil energy around 248 keV provides an interesting possibility to probe inelastic doublet dark matter (iDM). However, the electroweak doublet DM scenarios face strong constraints from solar DM capture for DM masses around the TeV scale which give rise to correct thermal relic density. In this work, we revive the inelastic doublet DM (iDM) scenario via type-II seesaw. In particular, we consider an inert lepton doublet (ILD) DM. While the minimal ILD scenario gives the correct relic abundance around the TeV scale, it is strongly constrained by direct detection and solar DM capture. In the type-II seesaw, the presence of the scalar triplet generates the required mass splitting and provides additional annihilation channels, allowing the correct relic abundance for much larger DM masses. The larger DM mass also helps evade the solar capture and indirect detection constraints. Additionally, the scalar triplet gives sub-eV neutrino masses required by the oscillation data.

We compute the gluonic contributions to the three-loop heavy-quark form factors for the vector, axial-vector, scalar, and pseudoscalar currents. In the low-energy limit, $q^2/m^2 \rightarrow 0$, we used guessing algorithms to derive closed-form difference and differential equations from the rational sequences associated with the multiple zeta values and other constants appearing in the expansion coefficients, which required up to 26000 coefficients in the most demanding cases. Part of the results are obtained analytically in terms of harmonic polylogarithms and square-root valued iterated integrals by solving the obtained differential equations. For the remaining contributions, arbitrarily deep series expansions around the singularities of the form factors can be obtained by matching local expansions at intermediate points and by exploiting the differential equations obeyed by the functions associated with each transcendental constant in the expansions around $s = q^2/m^2 = 0$. For all these calculations advanced computer algebra methods have been employed. By using analytic continuation methods for differential equations matching the expansions at different values of $s$ and using PSLQ, we derive analytic results in the high-energy limit, $q^2/m^2 \rightarrow \infty$. The expansion coefficients are expressed in terms of multiple zeta values up to weight $w = 6$ together with three additional constants, two related to sixth-root-of-unity letters and one associated with quadratic-form implied iterated integrals. We also derive deep expansions about the threshold and pseudo-threshold. Numerical results are presented in the whole kinematic range and compared to results in the literature.