The Lyman-$\alpha$ (Ly-$\alpha$) forest is a unique probe of cosmology and the intergalactic medium at high redshift and small scales. The statistical power of the ongoing Dark Energy Spectroscopic Instrument (DESI) demands precise theoretical tools to model the Ly-$\alpha$ forest. We present a hybrid effective field theory forward model in redshift space that leverages the accuracy of nonlinear particle displacements computed using the $N$-body simulation suite abacussummit with the predictive power of an analytical, perturbative bias forward model in the framework of the effective field theory. The residual noise between the model and the simulated Ly-$\alpha$ field has a nearly white (scale- and orientation-independent) power spectrum on quasilinear scales, substantially simplifying its modeling compared to a purely perturbative description. As a consequence of the improved control over the 3D Ly-$\alpha$ forest stochasticity, we find agreement between the modeled and the true power spectra at the 5% level down to scales of $k_{\max }\lesssim 1h{\mathrm{Mpc}}^{-1}$. This procedure offers a promising path toward constructing efficient and accurate emulators to predict large-scale clustering summary statistics for full-shape cosmological analyses of Ly-$\alpha$ forest data from both DESI and its successor, DESI-II.

We build upon previous analytical treatments of scalar perturbations in curved inflationary universes to obtain analytical templates for the primordial tensor power spectrum in models with nonzero primordial spatial curvature. These templates are derived without assuming a particular inflaton potential, within a background history consisting of an initial kinetically dominated phase followed by an ultraslow-roll inflationary regime, thereby isolating the universal imprints of curvature on tensor modes. Our results predict characteristic large-scale features—including low-$\ell$ cutoffs and oscillatory patterns—that are consistent with numerical solutions and provide a clear physical interpretation of how curvature modifies the underlying dynamics. In particular, we show that curvature effects manifest mathematically as systematic shifts in the dynamically relevant wave vectors, mirroring the behavior previously identified in the scalar power spectrum. These features translate into distinctive signatures in the large-angle $B$-mode polarization spectrum, offering a potential discriminant for spatial curvature in forthcoming cosmic microwave background observations.

Searches for neutrino isocurvature usually constrain a specific linear combination of isocurvature perturbations. In this work, we discuss realistic cosmological scenarios giving rise to neutrino isocurvature. We show that in general both neutrino and matter isocurvature perturbations are generated, whose ratio we parametrize by a newly introduced mixing angle. We obtain the first limits on this new mixing angle from PLANCK data, and discuss novel insights into the early Universe that could be provided by future measurements.

In this work, we investigate how short-range correlations affect relativistic hadronic models at high densities, with direct consequences for the structure of neutron stars, both with and without dark matter content. Two versions of the model are examined; one with vector self-interactions up to second order (${\omega }_0^2$) and another including a fourth-order term (${\omega }_0^4$). We show that short-range correlations tend to soften the equation of state when only the quadratic term is present, but produce a noticeable stiffening once the ${\omega }_0^4$ term is included. The corresponding Tolman-Oppenheimer-Volkoff solutions for pure neutron stars indicate that short-range correlations reduce the maximum mass in the first case but increase it in the second. Extending the analysis to stars containing a fermionic dark matter component, within the two-fluid formalism, we verify that the same features appear in the respective mass-radius diagrams. In particular, the decrease of the maximum mass with increasing dark matter fraction is partly compensated by the short-range correlation effects in the hadronic sector for the model with the fourth-order term. In all cases, the resulting parametrizations are consistent with recent astrophysical constraints, including the joint NICER-XMM-Newton analyses of the pulsars PSR $\mathrm{J}0030+0451$ and PSR $\mathrm{J}0740+6620$, as well as the gravitational-wave event GW190425.

We consider the possibility that gravity is mediated by “continuous spin” particles, i.e. massless particles whose invariant spin scale ${\rho }_g$ is nonzero. In this case, the primary helicity-2 modes of gravitational radiation on a Minkowski background mix with a tower of integer-helicity partner modes under boosts, with ${\rho }_g$ controlling the degree of mixing. We develop a formalism for coupling spinless matter to continuous spin gravity at linearized level. Using this formalism, we calculate the time-delay signatures induced by gravitational waves in an idealized laser interferometer detector. The fractional deviation from general relativity predictions is $O({\rho }_g/\omega )$ for gravitational wave frequencies $\omega >{\rho }_g$, and the effects of waves with $\omega \lesssim {\rho }_g$ are damped. The precision and low frequency ranges of gravitational wave detectors suggest potential sensitivity to spin scales at or below $\sim {10}^{-14}\mathrm{eV}$ at ground-based laser interferometers and $\sim {10}^{-24}\mathrm{eV}$ at pulsar timing arrays, motivating further analysis of observable signatures.

We examine the sensitivity of the beam normal spin asymmetry in Bhabha scattering to beyond the Standard Model mediators, in the context of the JLab polarized positron program. A key property of this observable is that the Standard Model contribution exhibits a zero crossing at a fixed scattering angle, providing a clean, effectively background-free point for these searches. We consider scalar, vector, and axial vector mediators and present projected bounds, finding that scalar and vector scenarios allow a significant extension of the search ranges beyond existing constraints.

We propose the “naive” $T$-odd Collins-Soper moments in the Drell-Yan process as probes of previously unexplored directions in the Standard Model effective field theory (SMEFT) parameter space. We show that the moments $A_6$ and $A_7$ in the high invariant mass and transverse momentum region are sensitive to dimension-8 $CP$-odd semileptonic four-fermion operators with an additional gluon field strength tensor. Using the projected integrated luminosity of a future high-luminosity LHC, we show that effective ultraviolet scales in the few-TeV range can be probed with this process.

Accelerator-based neutrino experiments offer a competitive environment to search for long-lived particles with sub-GeV masses. Yet, many theoretical models involving such particles predict very similar phenomenology and nearly identical final-state signatures. In view of this, we study the capabilities of upcoming experiments—specifically the DUNE near detectors—to distinguish between different classes of long-lived particles and the mechanisms by which they are produces. We expound how the experiment’s excellent energy resolution, combined with the possibility to move the detector off-axis (the DUNE-PRISM concept), work in tandem to improve the discrimination power.

The Wilson formulation of fermions in lattice gauge theory provides a unified description of the chiral anomalies in the standard model. The discrete Dirac operator diagonalizes into a series of $2\times 2$ blocks. In each block the possible eigenvalues either form a complex pair or separate into two real eigenvalues that have specific chirality. The collision of these pairs of eigenvalues occurs outside the perturbative region and provides a path between topological sectors.

The nature of the finite temperature phase transition of QCD depends on the particle density and the mass of the dynamical quarks. We discuss the properties of the phase transition at high density, considering an effective theory describing the high-density heavy-quark limit of QCD. This effective theory is a simple model in which the Polyakov loop is a dynamical variable, and the quark Boltzmann factor is controlled by only one parameter, $C(\mu ,m_q)$, which is a function of the quark mass $m_q$ and the chemical potential $\mu$. The Polyakov loop is an order parameter of $Z_3$ symmetry, and the fundamental properties of the phase transition are thought to be determined by the $Z_3$ symmetry broken by the phase transition. By replacing the Polyakov loop with $Z_3$ spin, we find that the effective model becomes a three-dimensional three-state Potts model ($Z_3$ spin model) with a complex external field term. We investigate the phase structure of the Potts model and discuss QCD in the heavy-quark region. As the density varies from $\mu =0$ to $\mu =\infty$, we find that the phase transition is first order in the low-density region, changes to a crossover at the critical point, and then becomes first order again. This strongly suggests the existence of a first-order phase transition in the high-density heavy-quark region of QCD.

We perform a systematical investigation of the existence of the deuteronlike singly bottomed dibaryon resonance states with strangeness $S=-1,-3,-5$ in the chiral quark model. Two resonance states with strangeness $S=-1$ are obtained in the baryon-baryon scattering process. The first candidate is $\mathrm{\Sigma }{\mathrm{\Sigma }}_b$ in the $\mathrm{\Lambda }{\mathrm{\Lambda }}_b$ and $N{\mathrm{\Xi }}_b^{*}$ scattering process, with the resonance energy 6974.22–6975.37 MeV and the decay width 14.450 MeV, respectively; the other one is $\mathrm{\Sigma }{\mathrm{\Sigma }}_b^{*}$ in the $N{\mathrm{\Xi }}_b$ and $N{\mathrm{\Xi }}_b^{\prime }$ scattering process, with the resonance energy 6990.69–7008.37 MeV and the decay width 43.790 MeV, respectively. The calculation of the distance between the center of mass of the two baryons shows that both $\mathrm{\Sigma }{\mathrm{\Sigma }}_b$ and $\mathrm{\Sigma }{\mathrm{\Sigma }}_b^{*}$ can be appropriately described as the deuteronlike dibaryons. Both of these resonance states are worthy of experimental exploration. Furthermore, it should be emphasized that the effect of channel coupling is of great importance in exploring exotic hadron states, and investigating the scattering process may serve as an effective approach to identifying genuine resonances.

We derive the unitarity constraints on anomalous quartic gauge couplings originating from the $f{\overline{f}}^{\prime }\to V{V}^{\prime }{V}^{\prime \prime }$ channel with $V^{({}^{\prime })({}^{\prime \prime })}=\gamma$, $Z$, $W^{\pm }$, and $H$. We also assess the importance of these bounds on the present and future experimental searches.

Using $4.5{\mathrm{fb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected by the BESIII detector at center-of-mass energies between 4.600 and 4.699 GeV, we search for the semileptonic decays ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^{+}{\pi }^{-}{e}^{+}{\nu }_e$ and ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^{-}{\pi }^{+}{e}^{+}{\nu }_e$ for the first time. Assuming their branching fractions are equal under isospin symmetry, evidence for ${\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^{\pm }{\pi }^{\mp }{e}^{+}{\nu }_e$ is reported with a significance of $3.6\sigma$. The corresponding branching fraction is measured to be $\mathcal{B}({\mathrm{\Lambda }}_c^{+}\to {\mathrm{\Sigma }}^{\pm }{\pi }^{\mp }{e}^{+}{\nu }_e)=({7.7}_{-{2.3}_{\mathrm{stat}}}^{+2.5}\pm {1.3}_{\mathrm{syst}})\times {10}^{-4}$, which is consistent with quark model predictions within two standard deviations.

We rely on Monte Carlo (MC) simulations to interpret searches for new physics at the Large Hadron Collider (LHC) and elsewhere. These simulations result in noisy and approximate estimators of selection efficiencies and likelihoods. In this context we pioneer an exact-approximate computational method—exact-approximate Markov chain Monte Carlo (MCMC), also known as pseudomarginal MCMC—that returns exact inferences despite noisy simulations. To do so, we introduce an unbiased estimator for a Poisson likelihood. We demonstrate the new estimator and new techniques in examples based on a search for neutralinos and charginos at the LHC using a simplified model. We find attractive performance characteristics—exact inferences are obtained for a similar computational cost to approximate ones from existing methods and inferences are robust with respect to the number of events generated per point. The unbiased estimator uses a Poisson-distributed number of MC events; it is also possible to construct a biased estimator whose bias decays factorially with increasing number of MC events.

At hadron colliders, the net transverse momentum of particles that do not interact with the detector (missing transverse momentum, ${\overrightarrow{p}}_{\mathrm{T}}^{\mathrm{miss}}$) is a crucial observable in many analyses. In the standard model, ${\overrightarrow{p}}_{\mathrm{T}}^{\mathrm{miss}}$ originates from neutrinos. Many beyond-the-standard-model particles, such as dark matter candidates, are also expected to leave the experimental apparatus undetected. This paper presents a novel deep neural network based ${\overrightarrow{p}}_{\mathrm{T}}^{\mathrm{miss}}$ estimator, deepmet, developed by the CMS Collaboration at the LHC. The deepmet algorithm produces a weight for each reconstructed particle based on its properties. The estimator is based on the negative vector sum of the weighted transverse momenta of all reconstructed particles in an event. Compared with other estimators currently employed by CMS, deepmet improves the ${\overrightarrow{p}}_{\mathrm{T}}^{\mathrm{miss}}$ resolution by 10%–30%, shows improvement for a wide range of final states, is easier to train, and is more resilient against the effects of additional proton-proton interactions accompanying the collision of interest.

We construct a smooth trajectory in Minkowski spacetime that is inertial in the asymptotic past and future but undergoes approximately uniform acceleration for a finite duration. In a suitable limit, this trajectory reduces to the standard Rindler trajectory, reproducing the expected Bogoliubov transformations and results consistent with the thermal time hypothesis. We analyze the behavior of an Unruh-DeWitt (UDW) detector following such a trajectory and explore the dependence of complete positivity (CP) divisibility on the detector’s frequency, acceleration, and the duration of acceleration. Notably, we find that the detector exhibits a memory effect due to the finite duration of acceleration, which is also quantified by the Fisher information. We further examine two UDW detectors along various trajectory combinations and show that, unlike the transition rate, both the total correlation and the entanglement harvested return smoothly to their initial values after the acceleration/deceleration phase. These correlation measures behave similarly in both accelerating and decelerating segments. Interestingly, we do not observe any measurable effect of the memory effect on negativity or mutual information. We also discuss the physical significance of the sign of the flux of acceleration-induced radiation.

The nonfactorizing nature of the Hilbert space in loop quantum gravity (LQG) due to gauge invariance requires a generalized definition of entanglement entropy. This work employs the framework of von Neumann algebras to investigate the entanglement entropy in LQG. On a graph, the holonomy and flux operators within a region and on the boundary generate a nonfactor type I von Neumann algebra, which is used to define the entanglement entropy for LQG states. This algebraic formalism is applied to “fixed-area states”—superpositions of spin networks associated with a surface with a definite macroscopic area given by the LQG area spectrum. By maximizing the entropy, we derive a geometrical area law where the entanglement entropy is proportional to the area. In addition, we show that bulk entanglement can renormalize the area-law coefficient and produce logarithmic corrections. The results in this paper closely relate to LQG black hole entropy.

A $B$-mode polarization signal in the cosmic microwave background (CMB) is widely regarded as smoking gun evidence for gravitational waves produced during inflation. Here, we demonstrate that tensor perturbations sourced during noninflationary epochs can yield non-negligible $B$-mode signals, which can in principle complicate the interpretation of future observational data. As a case study, we consider tensor perturbations sourced in the bubble collision stage of a first-order cosmological phase transition occurring in a secluded dark sector. Although phase transitions arise from causal subhorizon physics, they nevertheless exhibit a white noise power spectrum on superhorizon scales. Power is suppressed on the large scales relevant for CMB $B$-mode polarization, but it is not necessarily negligible. We show that for appropriately chosen phase transition parameters, the maximal $B$-mode amplitude can compete with inflationary predictions that can be tested with current and future experiments. These scenarios can be differentiated by performing measurements on multiple angular scales, since the phase transition signal predicts peak power on smaller scales.

We show that persistence-based topology of the 21 cm forest encodes information about Cosmic Dawn that is complementary to traditional amplitude- or correlation-based statistics. Applying topological data analysis to simulated one-dimensional forest spectra over a grid of x-ray heating efficiencies $f_X$ and warm-dark-matter (WDM) masses $m_{\mathrm{WDM}}$ (which set the free-streaming scale), we construct persistence diagrams and Betti-0 curves that track the birth-merger hierarchy of absorption troughs under sublevel filtrations. From these summaries, we define three interpretable descriptors: the trough line density $\lambda (t_{\star })$, the total squared persistence $M_2={\sum }_{j\in {\mathcal{I}}_{\mathrm{long}}}{\tau }_j^2$ where ${\mathcal{I}}_{\mathrm{long}}\equiv \{j|{\tau }_j\ge {\tau }_{\star }\}$ denotes long-lived components, and the Betti-curve asymmetry $A_{\mathrm{skew}}$. In a Fisher forecast around a fiducial WDM model, $\lambda (t_{\star })$ and $A_{\mathrm{skew}}$ provide strong local leverage on the heating axis, while $M_2$ retains appreciable sensitivity to the free-streaming scale and supplies an inclined constraint direction that reduces the remaining degeneracy in the $(f_X,m_{\mathrm{WDM}})$ plane. We further demonstrate that, under an SKA1-Low-like uncorrelated thermal-noise model, noise predominantly produces short-lived fluctuations that are removed by imposing the same persistence-lifetime cut ${\tau }_j\ge {\tau }_{\star }$, leaving the topology of long-lived troughs and the gross Betti-curve morphology largely intact. These results establish persistence-based descriptors as a robust non-Gaussian probe of small-scale structure and heating during Cosmic Dawn, naturally complementing power-spectrum and wavelet-based analyses.

We propose a novel mechanism where a first-order phase transition modulates the decay rate of a massive field. This modulation, even if the scalar field has negligible energy density, subsequently generates an observable stochastic gravitational-wave (GW) background. The stochastic nature of bubble nucleation leads to the asynchrony of phase transitions, generating superhorizon-scale density perturbations through spatial variations in the decay rate $\mathrm{\Gamma }$. These perturbations subsequently source second-order GWs with peak amplitudes governed by the phase transition parameter $\beta /H_{*}$ and decay rate $\mathrm{\Gamma }$. We apply this mechanism in the reheating scenario where the decay rate of the inflaton is modulated by the scalar field that undergoes a first-order phase transition. Numerical calculations reveal that the GW energy spectrum typically reaches ${\mathrm{\Omega }}_{\mathrm{GW}}\sim {10}^{-10}$, demonstrating prospects for detection by space-based interferometers like Laser Interferometer Space Antenna, TianQin, and Taiji. This work establishes a new approach to probe phase transition processes in the early Universe without requiring significant vacuum energy release.