In the context of a theory of minimally modified gravity, the $V(\varphi )$ cold dark matter (VCDM), one can realize any cosmological behavior at the level of the homogeneous and isotropic background without introducing fatal instabilities for perturbations. Therefore, VCDM provides a theoretically consistent and observationally testable framework of dynamical dark energy parametrizations with or without phantom behaviors. In this paper, we propose the VCDM realizations of various phenomenological parametrizations present in the literature: the Chevallier-Polarski-Linder, Barboza-Alcaniz, Jassal-Bagla-Padmanabhan, exponential, and logarithmic models. Using the VCDM equations for cosmological perturbations, we test them against the recent cosmological datasets, Planck 2018 and DESI baryon acoustic oscillation data release 2, and then discuss their implications.

Critical behavior and ultraviolet scaling of induced gravitational waves (GWs) from an early matter-dominated (eMD) era are studied in the context of primordial black hole evaporation. The depth of the eMD is characterized by the minimum parameter of the equation of state ${\omega }_{\min }$ that the Universe can attain during this phase. We identify a critical value ${\omega }_c\sim 7.3\times {10}^{-3}$ that separates two regimes. For ${\omega }_{\min }<{\omega }_c$, the GW peak lies at the nonlinear cutoff point and requires nonlinear dynamics. For ${\omega }_{\min }>{\omega }_c$, the peak originates from modes that reenter near the matter-radiation equality, and the ultraviolet tail follows a distinct scaling $k^{-3/2}$. This critical behavior provides a clear definition of deep versus shallow eMD and a robust spectral signature for future GW observations.

We investigate the cosmological imprint of self-interacting dark radiation (DR) on the primordial $B$-mode angular power spectrum and its impact on the estimation of the tensor-to-scalar ratio $r$. We consider a minimal model in which DR is described as an effectively massless axionlike particle with quartic self-interactions. These interactions are incorporated into the Einstein–Boltzmann equations using the relaxation time approximation and implemented in the CLASS code. We show that increasing the strength of DR self-interactions suppresses anisotropic stress, thereby reducing the damping of gravitational waves and leading to an enhancement of the primordial $B$-mode signal relative to the free-streaming case. Using mock CMB data and Markov Chain Monte Carlo analyses, we show that neglecting DR self-interactions may bias the inferred value of $r$ by an amount comparable to the uncertainty expected in forthcoming CMB polarization experiments, such as the ground-based Simons Observatory and the satellite missions LiteBIRD and Probe of Inflation and Cosmic Origins. Our results emphasize the importance of properly modeling DR interactions in future precision searches for primordial $B$-modes in order to obtain unbiased constraints on inflationary gravitational waves.

We present constraints on isotropic cosmic birefringence induced by axion-like particles (ALPs), derived from the analysis of cosmic microwave background (CMB) polarization measurements obtained with the high-frequency channels of Planck. Recent measurements report a hint of isotropic cosmic birefringence, though its origin remains uncertain. The detailed dynamics of ALPs can leave characteristic imprints on the shape of the $EB$ angular power spectrum, which can be exploited to constrain specific models of cosmic birefringence. We first construct a multifrequency likelihood that incorporates an intrinsic nonzero $EB$ power spectrum. We also show that the likelihood used in previous studies can be further simplified without loss of generality. Using this framework, we simultaneously constrain the ALP model parameters, the instrumental miscalibration angle, and the amplitudes of the $EB$ power spectrum of a Galactic dust foreground model. We find that, if ALPs are responsible for the observed cosmic birefringence, ALP masses at ${\log }_{10}{m}_{\varphi }[\mathrm{eV}]\simeq -27.8$, $-27.5$, $-27.3$, $-27.2$, $-27.1$, as well as ${\log }_{10}{m}_{\varphi }[\mathrm{eV}]\in [-27.0,-26.5]$, are excluded at more than $2\sigma$ statistical significance.

IceCube has recently reported the detection of $\sim 1–10\mathrm{TeV}$ neutrinos from the nearby active galaxy, NGC 1068. The lack of TeV-scale emission from this source suggests that these neutrinos are generated in the dense corona that surrounds NGC 1068’s supermassive black hole. In this paper, we present a physical model for this source, including the processes of pair production, pion production, synchrotron, and inverse Compton scattering. We have also performed a new analysis of Fermi-LAT data from the direction of NGC 1068, finding that the gamma-ray emission from this source is very soft but bright at energies below $\sim 1\mathrm{GeV}$. Our model can predict a gamma-ray spectrum that is consistent with Fermi-LAT observations when the magnetic field within the corona of this active galactic nucleus (AGN) is quite high, namely $B\gtrsim 6\mathrm{kG}$. To explain the observed neutrino emission, this source must accelerate protons with a total power that is comparable to its intrinsic x-ray luminosity. In this context, we consider two additional nearby active galaxies, NGC 4151 and NGC 3079, which have been identified as promising targets for IceCube.

The origin of Galactic cosmic rays (CRs), particularly around the knee region ($\sim 3\mathrm{PeV}$), remains a major unanswered question. Recent observations by LHAASO suggest that the knee is shaped mainly by protons, with a transition to heavier elements at higher energies. Microquasars—compact jet-emitting sources—have emerged as possible PeV CR accelerators, especially after detections of ultrahigh-energy gamma rays from these systems. We propose that the observed proton spectrum (hard below a few PeV, steep beyond) arises from the reacceleration of sub-TeV Galactic CRs via shear acceleration in large-scale microquasar jet-cocoon structures. Our model also naturally explains the observed spectrum of energies around a few tens of PeV by summing up heavier nuclei contributions. Additionally, similar reacceleration processes in radio galaxies can contribute to ultrahigh-energy CRs, bridging Galactic and extragalactic origins. Combined with low-energy CRs from supernova remnants and galaxy clusters around the second knee region, this scenario could provide a unified explanation for CRs across the entire energy spectrum.

Employing the principle of quantum teleportation in gravitational-wave detectors provides a method to address technical challenges associated with implementing quantum filters for squeezed-light injection. A recent proposal [Phys. Rev. A 110, 022601] has shown that an arbitrary number of effective squeezing-angle rotations can be achieved by cascading quantum teleportation, yielding sensitivity equivalent to frequency-dependent prefiltering. A natural question is whether the teleportation-based protocol can also realize frequency-dependent postfiltering. In this work, we examine this possibility and show that, with perfect teleportation fidelity, postfiltering can be fully implemented. In practice, however, various imperfections make the sensitivity nearly equivalent to that of teleportation-based prefiltering. We apply this scheme to the low-frequency detector in the Einstein Telescope xylophone configuration and find that teleportation-based postfiltering could also be a candidate for the detector’s design.

The Michelson interferometric phase detection resolution can be enhanced by replacing conventional beam splitters with novel directionally unbiased four-port scatterers, such as Grover coins. We present a quantitative analysis of the noise-to-signal ratio of sideband frequencies generated by gravitational-wave-induced phase perturbations in a Grover-Michelson interferometer (GMI). We discuss the principles of GMI signal enhancement and demonstrate how combining this configuration with additional light recycling arrangements further enhances the performance.

In this paper, we utilize the maximum entropy prescription to determine a quantum state of a small collision system at the kinetic freeze-out. We derive expressions for multiplicity-selected particle momentum spectra and correlation functions by applying a fixed particle number constraint to this state. The results of our analysis can be useful for interpreting the multiplicity dependence of the particle momentum spectra and correlations in high-multiplicity $pp$ collision events at a fixed LHC energy.

To resolve ambiguities from multiple solutions in experimental measurements, we construct a ${\chi }^2$ function incorporating constraints such as isospin conservation and amplitude relations. By minimizing the global ${\chi }^2$, we identify physical solutions for seven hidden-charm decay channels of $Y(4230)$. Crucially, the physical solution for $Y(4230)\to {\pi }^{+}{\pi }^{-}J/\psi$ corresponds to the largest among four experimental solutions, potentially modifying inputs for theoretical calculations. Additionally, we predict ${\mathrm{\Gamma }}_{ee}\mathcal{B}(Y(4230)\to {\pi }^{+}{\pi }^{-}{\psi }^{\prime })$ based on our results, acknowledging substantial uncertainties in current measurements.

Domain wall (DW) networks may have formed in the early Universe following the spontaneous breaking of a discrete symmetry. Notably, several particle physics models predict the existence of current-carrying DWs, which can capture and store particles as zero modes on it. In this study, we demonstrate that gravitational waves (GWs) generated by current-carrying DWs with fermionic zeromodes exhibit a novel feature: an additional peak with a distinct spectral shape in the GW spectrum resembling mountains, arising from metastable topological remnants, which we term “spherons.” This distinct signature could be detectable in upcoming GW observatories such as LISA. The results suggest that DW networks in beyond Standard Model scenarios could emit GW signals that are significantly stronger and with greater detectability than previously expected.

We formulate a light-front model for the pion that explicitly incorporates the gluonic degree of freedom. In this framework, high-energy scattering off the pion is described by an active gluon, while the remaining constituents are treated as a spectator system with an effective mass. The mass spectrum and light-front wave functions (LFWFs) of the pion are determined by solving two Schrödinger-like equations derived from quantum chromodynamics: the light-front holographic equation in the chiral limit and the ’t Hooft equation. Using the resulting LFWFs, we compute the gluon distributions within pion, including the parton distribution functions in comparison with the available global fits, generalized parton distributions, and transverse momentum-dependent distributions. The present analysis is restricted to the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi domain of the pion’s gluon generalized parton distribution, without explicit construction of the Efremov-Radyushkin-Brodsky-Lepage region. Consequently, the polynomiality condition for full Mellin moments is not satisfied by construction. Furthermore, we demonstrate that the obtained LFWFs provide a good description of the gravitational form factors of pion when compared with the recent lattice QCD results.

We compare the fixed-order NLO QCD predictions for the $pp\to t\overline{t}t\overline{t}+X$ process in the $4\ell$ decay channel with the parton-shower-based results obtained with the powheg and mc@nlo matching methods. In the first case, NLO QCD corrections are consistently included in both the $t\overline{t}t\overline{t}$ production step and the decays of the four top quarks, preserving all spin correlations. In the second approach, higher-order effects in top-quark decays with approximate spin correlations are simulated in the pythia parton-shower framework. Additionally, we analyze the impact of including the so-called matrix element corrections in top-quark decays in both parton-shower matched predictions. The comparison is performed at the integrated and differential fiducial cross-section level for the LHC center-of-mass energy of $\sqrt{s}=13.6\mathrm{TeV}$.

The LHCb Collaboration has recently found a large $CP$-violating rate asymmetry in the $b$-baryon decay ${\mathrm{\Lambda }}_b^0\to p{K}^{-}{\pi }^{+}{\pi }^{-}$. This is the first observation of $CP$ violation in baryon processes, opening a new window to test its standard model (SM) origin. Many more baryon decays are expected to exhibit observable signals of $CP$ violation. We show that there also exists large $CP$ violation in the U-spin partner decay mode, ${\mathrm{\Xi }}_b^0\to {\mathrm{\Sigma }}^{+}{\pi }^{-}{K}^{+}{K}^{-}$, with rate asymmetry $A_{CP}({\mathrm{\Xi }}_b^0\to {\mathrm{\Sigma }}^{+}{\pi }^{-}{K}^{+}{K}^{-})=-A_{CP}({\mathrm{\Lambda }}_b^0\to p{K}^{-}{\pi }^{+}{\pi }^{-})\frac{\mathrm{Br}({\mathrm{\Lambda }}_b^0\to p{K}^{-}{\pi }^{+}{\pi }^{-})}{\mathrm{Br}({\mathrm{\Xi }}_b^0\to {\mathrm{\Sigma }}^{+}{\pi }^{-}{K}^{+}{K}^{-})}\frac{{\tau }^{{\mathrm{\Xi }}_b}}{{\tau }^{{\mathrm{\Lambda }}_b}}$ in the U-spin symmetry limit. By neglecting a subleading contribution in the amplitudes, $A_{CP}({\mathrm{\Lambda }}_b^0\to p{\pi }^{+}{\pi }^{-}{\pi }^{-})=-(12\pm 6)\%$. These predictions can be tested in the near future.

We analyze the vacuum fluctuations and the stress-energy tensor of a scalar field of mass $M$ in a conical spacetime, where the topological singularity at the apex requires boundary conditions for the field equation. The necessity of boundary conditions was established by Kay and Studer in the early 1990s, while for $M=0$ stability is achieved only under Dirichlet boundary conditions, and for $M>q$ the field is stable and a localized mode emerges. This mode admits a natural interpretation as a covariant model of an extended particle detector, which allows us to investigate how such detectors modify the local vacuum structure. In this framework, the renormalized stress-energy tensor offers a natural way to quantify the influence of the detector on the surrounding spacetime.

We consider the Chern-Simons theory coupled to massive fundamental matter in three spacetime dimensions, focusing on the Higgsed phase of the bosonic matter in the large-$N$ limit. To study the characteristics of the $Z$ boson in the Higgsed phase and address an apparent puzzle regarding its fermionic analog, we employ the 3D Bose-Fermi duality to derive the exact large-$N$ result for the two-point function of the $Z$ boson. We study the spectral representation of the $Z$ boson and find that, in the large-$N$ limit, it behaves as an unstable resonance with a nonperturbatively large lifetime at weak coupling.

We show that the Seiberg-type duality of $\mathcal{N}=1$ gauge theory coupled with tensor chiral fields and fundamental chiral fields works if the meson spectrum built from the tensor fields takes a particular form: (a) It should be truncated. (b) The $R$ charges of tensor fields $\{R_a\}$ and the truncated mesons $\{R_j\}$ take very special values. The meson spectrum so that the duality works is encoded elegantly in the factorization of the polynomial $y^n-1={\mathrm{\Phi }}_{+}{\mathrm{\Phi }}_{-}$. Our consideration covers many known $\mathcal{N}=1$ dualities and generates a large class of new examples.

Recent investigations of vacuum polarization in extremely compact stars suggest that, in such regimes, the effective matter content of spacetime may acquire a vacuum-energy equation of state with negative energy density, mimicking a negative cosmological constant. Motivated by this observation, we introduce a general algorithm to modify well-known spherically symmetric regular black hole metrics by replacing their usual de Sitter cores (dSC) with anti–de Sitter cores (AdSC). Like their dSC counterparts, these AdSC solutions may exhibit two, one, or no horizons depending on the value of a regularization parameter $\ell$. We present explicit examples of AdSC-Bardeen and AdSC-Dymnikova metrics, analyze their main properties, and investigate some of their phenomenological signatures using test fields. In particular, we compare their fundamental quasinormal modes and echo signals with those of the dSC cases, highlighting potential avenues for distinguishing them observationally.

This paper explores modifications to general relativity by considering higher-order curvature terms in the gravitational action, specifically focusing on the quadratic Ricci scalar and a particular cubic contraction of the Riemann tensor. These modifications introduce new interactions at short distances, potentially altering the dynamics of compact objects. We calculate the effective two-body binding potential energy for these modified theories to quantify these effects using the worldline effective field theory formalism. This approach allows us to systematically integrate out short-distance gravitational effects, capturing the modifications to the binding potential. Our results demonstrate how the quadratic Ricci scalar and cubic Riemann tensor terms contribute to the two-body interaction at the leading order, highlighting deviations from classical general relativity predictions. These findings offer insight into the potential observational signatures of modified gravity theories in binary systems and other astrophysical settings.