The enhancement of weak signals and the detection of hypothetical particles facilitated by quantum amplification are crucial for advancing fundamental physics and its practical applications. Recently, it was experimentally observed that a magnetic field can be amplified by using nuclear spins under Markovian noise [H. Su et al., New constraints on axion-mediated spin interactions using magnetic amplification, Phys. Rev. Lett. 133, 191801 (2024).]. Here, we theoretically propose amplifying the magnetic-field signal by using nuclear spins by the quantum Zeno effect (QZE). Under identical conditions, we demonstrate that compared to the Markovian case the amplification of the weak magnetic field can be enhanced by a factor about $e^{1/2}$ under a Gaussian noise. Moreover, through numerical simulations we determine the optimal experimental parameters for amplification conditions. This work shows that the combination of the QZE and spin amplification effectively enhances the amplification of the weak magnetic field. Our findings may provide valuable guidance for the design of experiments on establishing new constraints of dark matter and exotic interactions in the near future.

We numerically simulate the formation of primordial black holes (PBHs) in a radiation-dominated Universe under the assumption of spherical symmetry, driven by the collapse of adiabatic fluctuations, for different curvature profiles $\zeta$. Our results show that the threshold for PBH formation, defined as the peak value of the critical compaction function ${\mathcal{C}}_c(r_m)$ (where $r_m$ is the scale at which the peak occurs), does not necessarily asymptotically saturate to its maximum possible value in the type-I region for sufficiently sharp profiles. Instead, the threshold is found in the type-II region with ${\mathcal{C}}_c(r_m)$ being a minimum. We find, for the cases tested, that this is a general trend associated with profiles that exhibit extremely large curvatures in the linear component of the compaction function ${\mathcal{C}}_l(r)\equiv -4r{\zeta }^{\prime }(r)/3$ shape around its peak $r_m$ (spiky shapes). To measure this curvature at $r_m$, we define a dimensionless parameter, $\kappa \equiv -r_m^2{\mathcal{C}}_l^{\prime \prime }(r_m)$, and we find that the thresholds observed in the type-II region occur for sufficiently large $\kappa$ for the profiles we have used, contrary to expectations. By defining the threshold in terms of ${\mathcal{C}}_{l,c}(r_m)$, we extend previous analytical estimations to the type-II region, which is shown to be accurate within a few percent when compared to the numerical simulations for the tested profiles. Our results suggest that current PBH abundance calculations for models where the threshold lies in the type-II region may have been overestimated due to the general assumption that it should saturate at the boundary between the type-I and type-II regions.

Simulation-based inference (SBI) allows fast Bayesian inference for simulators encoding implicit likelihoods. However, some explicit likelihoods cannot be easily reformulated as simulators, hindering their integration into combined analyses within SBI frameworks. One key example in cosmology is given by the Planck cosmic microwave background (CMB) likelihoods. We present a simple method to construct an effective simulator for any explicit likelihood using samples from a previously converged Markov Chain Monte Carlo (MCMC) run. This effective simulator can subsequently be combined with any forward simulator. To illustrate this method, we combine the full Planck CMB likelihoods with a $3\times 2\mathrm{pt}$ simulator (cosmic shear, galaxy clustering and their cross-correlation) for a stage IV survey like Euclid, and test evolving dark energy parametrized by the $w_0{w}_a$ equation of state. Assuming the $w_0{w}_a$ cold dark matter cosmology hinted by the Dark Energy Spectroscopic Instrument baryon acoustic oscillations (BAO) data release 2 + Planck 2018 + PantheonPlus supernovae Ia (SNIa) datasets, we find that future $3\times 2\mathrm{pt}$ data alone could detect evolving dark energy at $5\sigma$, while its combination with current CMB, BAO, and SNIa datasets could raise the detection to almost $7\sigma$. Moreover, thanks to simulation reuse enabled by SBI, we show that our joint analysis is in excellent agreement with MCMC while requiring zero Boltzmann solver calls. This result opens up the possibility of performing massive global scans combining explicit and implicit likelihoods in a highly efficient way.

We consider non-Gaussianity in open quantum systems by finding and characterizing exact ground states of nonlinearly coupled anharmonic oscillators. Tracing out the hidden sector oscillator, we find that the non-Gaussianity of the observable mode may be either enhanced or suppressed by nonlinear coupling to a hidden, non-Gaussian mode. We use a known family of quasiexactly solvable anharmonic oscillators to construct exact, rather than perturbative, ground state solutions. These include states of extreme classical non-Gaussianity and strong quantum non-Gaussianity (infinite stellar rank). The calculation generalizes the classic, bilinearly coupled oscillator example, used for the black hole area law, to non-Gaussian quantum states whose entanglement properties are more complex. If the visible sector field is nondynamical and plays the role of a coupling parameter in the late universe, our results suggest novel statistics for disordered, or space-time dependent, couplings. This class of constructions allows useful exploration of strongly non-Gaussian states and fields, including a means to characterize the robustness of non-Gaussianity to interactions with environmental modes.

In this article, we calculate the mass distribution of primordial black holes (PBHs) formed in the matter-dominated (MD) era by the peak theory. We apply the Zel’dovich approximation to track the nonlinear evolution of overdensities and compute the PBH abundance and mass function by incorporating a PBH formation criterion based on the hoop conjecture. We find that the PBH abundance $\beta$ follows the scaling law $\beta \simeq A_{\gamma }{\sigma }_h^{*5}$ for ${\sigma }_h^{*}\ll 1$. Here, ${\sigma }_h^{*}$ is the quantity that characterizes the variance of the density fluctuation at the horizon entry. We also find that, in contrast to the previous estimates, the PBH spin is very small for ${\sigma }_h^{*}\ll 1$ but could be larger for larger ${\sigma }_h^{*}$ and broader power spectra. Finally, specializing to a monochromatic power spectrum, we prove analytically that the PBH mass distribution becomes effectively monochromatic and reveal that the resultant PBH abundance is approximately 19 times the previous prediction.

Based on considerations of quantum gravity, global symmetries which lead to axions as pseudo- Nambu-Goldstone bosons after low scale symmetry breaking cannot be exact at the Planck scale. Here, we show that Planck-suppressed terms which yield this symmetry breaking may provide a noninflationary misalignment mechanism which can generate coherent oscillations of the axion and axionlike particle (ALP) fields at low temperatures.

Recent James Webb Space Telescope observations of high-redshift massive galaxy candidates have initiated renewed interest in the important mystery around the formation and evolution of our Universe’s largest supermassive black holes (SMBHs). We consider the possibility that some of them were seeded by the direct collapse of primordial density perturbations from inflation into primordial black holes and analyze the consequences of this on current dark matter substructures assuming non-Gaussian primordial curvature perturbation distributions. We derive bounds on the enhanced curvature perturbation amplitude from the number of dwarf spheroidal galaxies in our Galaxy, observations of stellar streams and gravitational lensing. We find this bound region significantly overlaps with that required for SMBH seed formation and enables us to probe Gaussian and non-Gaussian curvature perturbations corresponding to the SMBH seeds in the range $\mathcal{O}({10}^5–{10}^{12})M_{\odot }$.

The gravitational wave signature from core-collapse supernovae (CCSNe) is dominated by quadrupolar oscillation modes of the newly born protoneutron star (PNS), and could be detectable at galactic distances. We have developed a framework for computing the normal oscillation modes of a PNS in general relativity, including, for the first time, the presence of an accretion flow and a surrounding stalled accretion shock. These new ingredients are key to understanding PNS oscillation modes, in particular those related to the standing accretion shock instability. Their incorporation is an important step toward accurate PNS asteroseismology. For this purpose, we perform linear and adiabatic perturbations of a spherically symmetric background, in the relativistic Cowling approximation, and cast the resulting equations as an eigenvalue problem. We discretize the eigenvalue problem using collocation Chebyshev spectral methods, which is then solved by means of standard and efficient linear algebra methods. We impose boundary conditions at the accretion shock compatible with the Rankine-Hugoniot conditions. We present several numerical examples to assess the accuracy and convergence of the numerical code, as well as to understand the effect of an accretion flow on the oscillation modes, as a stepping stone toward a complete analysis of the CCSNe case.

We propose a novel mechanism to generate primordial magnetic fields (PMFs) strong enough to explain the observed cosmic magnetic fields. We employ a scalar field charged under U(1) gauge symmetry with a nontrivial vacuum expectation value to provide an effective mass term to the electromagnetic field and thus break its conformal invariance. The primordial magneto-genesis takes place in the radiation dominated (RD) epoch, after the electroweak symmetry breaking (EWSB) phase. As a result, our mechanism is naturally free from the over-production of electric fields due to high conductivity in the RD epoch, and the baryon isocurvature problem which takes place only if magneto-genesis happens before the ESWB phase. In addition, we find that a significant amount of PMFs can be generated when the scalar field experiences a tachyonic phase. In this case, the scalar field is light and weakly coupled and has negligible energy density compared to the cold dark matter, hence the strong coupling problem and the backreaction problem are also absent. Therefore, our model is free from the above-mentioned problems that frequently appear in other primordial magneto-genesis scenarios.

Quantum simulation is a rapidly evolving tool with great potential for research at the frontiers of physics, and is particularly suited to be used in computationally intensive lattice simulations, such as problems with nonequilibrium. In this work, a basic scenario, namely free fermions in an expanding universe, is considered, and quantum simulations are used to perform the evolution and study the phenomena involved. Using digital quantum simulations with the Jordan-Wigner transformation and Trotter decomposition, the evolutions of fermion number density, correlation functions, polarization, and chiral condensation are analyzed. A spread out phenomenon can be observed in the simulation, which is a consequence of momentum redshift. This work also demonstrates the simplicity and convenience of using quantum simulations when studying time evolution problems.

We investigate the impact of momentum-dependent relaxation time approximation in the Boltzmann equation within the Bjorken flow framework by analyzing the moments of the single-particle distribution function. The moment equations, which form an infinite hierarchy, provide important insights about the system dynamics and the approach towards equilibrium for systems far from equilibrium. The momentum-dependent collision kernel couples moments through both the energy exponents and the angular dependence via various-order Legendre polynomials, resulting in an intricate system of infinitely coupled equations. A naive truncation of the coupled equations results in diverging moments at late times. We outline strategies for solving the coupled system, including a novel approach for managing the divergences and noninteger moments. We show a significant influence of momentum-dependent relaxation time on the time evolution of the moments, particularly for higher-order moments and systems with smaller shear viscosity over entropy density, emphasizing the importance of incorporating such dependence for a more accurate description of the system dynamics with low shear viscosity such as the quark-gluon-plasma produced in high-energy heavy-ion collisions.

The dynamics of quantum fields become nonperturbative when their interactions are probed by a large number of particles. To explore this regime, we study correlation functions that involve a large number of fields, focusing on massive scalar theories that feature arbitrary self-interactions, ${\varphi }^{2p}$. Treating quantum fields as operator-valued distributions, we investigate $n$-point correlation functions at ultrashort distances and compute moments and cumulants of fields, using a semiclassical saddle point approximation in the double scaling limit of weak coupling, $\lambda \to 0$, large quantum number, $n\to \infty$, while keeping $\lambda n$ constant. Addressing the nonperturbative regime, where $\lambda n\gtrsim 1$, requires a resummation of the effective saddle point to all orders in $\lambda n$. We perform this resummation in zero and one dimensions and show that the moments, corresponding to correlation functions including disconnected contributions, grow exponentially with $n$. This growth is significantly reduced for higher-order self-interactions, i.e., for larger $p$. On the other hand, we argue that the cumulants, which represent connected correlation functions, grow even more rapidly and are mostly independent of $p$.

Scalar extensions of the Standard Model (SM) are of much interest at the Large Hadron Collider (LHC) and future colliders. In particular, these models can give rise to resonant di-Higgs production and alter the Higgs trilinear coupling. In this paper, we study di-Higgs production in the Standard Model extended by a real scalar singlet with no additional symmetries. We determine how large the resonant di-Higgs rate and variation in the Higgs trilinear coupling can be in four scenarios: current LHC results and projected results at the high luminosity LHC (HL-LHC), the HL-LHC combined with a circular $e^{-}{e}^{+}$ collider such as the Circular Electron Positron Collider or Future Circular Collider with electron-positron collisions, and the HL-LHC combined with a linear $e^{-}{e}^{+}$ collider such as the International Linear Collider. While these are updated results from a previous study by [I. M. Lewis and M. Sullivan, Benchmarks for double Higgs production in the singlet extended standard model at the LHC, Phys. Rev. D 96, 035037 (2017).] using current LHC data, we go further and find benchmark points in the multi-TeV resonance regime for future colliders beyond the HL-LHC. Considering current LHC results, the resonant di-Higgs rate can still be an order of magnitude larger than the SM predicted di-Higgs rate. In the HL-LHC scenario, the Higgs trilinear coupling can still be a factor of three larger than the SM prediction for resonance masses in the 1.5–3.5 TeV range, where resonant searches may have less reach. This enhancement is just at the projected $2\sigma$ sensitivity of the HL-LHC. We find there are resonance masses for which the change in the Higgs trilinear is maximized while the resonant rate is negligible. We provide an analytical understanding of these effects with a discussion on the interplay of various constraints on the parameter space and the Higgs trilinear coupling.

We study the implications of noninvertible chiral symmetry in a four-dimensional U(1) gauge theory coupled to massless fermions with electromagnetic $SL(2,\mathbb{Z})$ duality. This is done by deriving the Adler-Bell-Jackiw anomaly of massless QED in the dual frame that is used to explicitly construct the symmetry defect operator as well as the conserved two-form symmetry current. As expected, the noninvertible chiral symmetry is covariant under the duality transformation. This has implications for understanding the nature of kinetic and topological terms in the dual frame and for axion electrodynamics. In particular, we show that to generate an axion potential from a dyon loop, the one-form magnetic symmetry must be explicitly broken by a mutually nonlocal charged state with nonzero pairwise helicity.

We study a $U(1)\otimes U(1)$ system coupled to scalar fields. Initially, the model is studied in a novel continuum formulation and study of the appropriate diagonalizations is performed. Three models are examined, in two of which the scalar field couples with both gauge fields while in the third one the scalar field couples only to the dark photon. The model is then treated on a space-time lattice. We determine the phase diagram for various values of the kinetic coupling parameter. Then there follows the determination of masses for the scalar fields and the massive gauge fields, as well as the fine structure constants for the massless gauge fields.

The charge asymmetry in the process $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}{\pi }^0\gamma$ is studied for photons with energies $\nu \ll \sqrt{s}$. The longitudinal polarization of electrons (positrons) is taken into account. The asymmetry arises due to interference of the amplitudes for production of pion states with opposite $C$ parities. The contribution of the $a_1^0(1260)$ meson in the intermediate state to the charge asymmetry is discussed. This contribution is not the leading one, however it is not negligible. It is shown that the charge asymmetry can reach several tens of percent.

We use Pomeron evolution equation in zero transverse dimension based on the Abramovskii-Gribov-Kancheli (AGK) cutting rules to calculate the von Neumann entropy and $q$ moments that are used as an experimental test for the Koba-Nielsen-Olesen scaling. In order to avoid the negative probabilities that emerge from the negative AGK weights in the Minkowski space, we reformulate the Pomeron evolution in the Euclidean space. The resulting positive definite probabilities for cut and uncut Pomerons are used in calculating the $q$ moments. The comparison to the experimental data shows that our AGK-based model successfully describes $q$-moment dependence on the mean multiplicity without any adjustable parameter in the experimental data of the $p\text{−}p$ collisions by the ALICE Collaboration.

The study of solar neutrinos presents significant opportunities in astrophysics, nuclear physics, and particle physics. However, the low-energy nature of these neutrinos introduces considerable challenges to isolate them from background events, requiring detectors with low-energy threshold, high spatial and energy resolutions, and low data rate. We present the study of solar neutrinos with a kiloton-scale liquid argon detector located underground, instrumented with a pixel readout using the Q-Pix technology. We explore the potential of using volume fiducialization, directional topological information, light signal coincidence, and pulse-shape discrimination to enhance solar neutrino sensitivity. We find that discriminating neutrino signals below 5 MeV is very difficult. However, we show that these methods are useful for the detection of solar neutrinos when external backgrounds are sufficiently understood and when the detector is built using low-background techniques. When building a workable background model for this study, we identify $\gamma$ background from the cavern walls and from capture of $\alpha$ particles in radon decay chains as both critical to solar neutrino sensitivity and significantly underconstrained by existing measurements. Finally, we highlight that the main advantage of the use of Q-Pix for solar neutrino studies lies in its ability to enable the continuous readout of all low-energy events with minimal data rates and manageable storage for further off-line analyses.

The neutrino fast flavor instability dominates the evolution of neutrino flavor within the engines of core-collapse supernovae and neutron star mergers. However, theoretical models of neutrino flavor change that include many-body quantum correlations can differ starkly from similar mean-field calculations. We demonstrate for the first time that the inhomogeneous fast flavor instability is disrupted by many-body correlations using a novel tensor network framework that allows a continuous transition between mean-field and many-body results by tuning the singular value decomposition cutoff value. Generalizing the forward-scattering Hamiltonian to spatially varying conditions, we demonstrate that the timescale of flavor transformation scales logarithmically with system size, suggesting that many-body effects could occur before mean-field instabilities are able to saturate. Our results have significant implications for astrophysical explosion dynamics, nucleosynthesis, and observable neutrino signatures.

We investigate the emergent factorization of Hilbert space in the low-energy description of matrix models, addressing key aspects of the black hole information paradox. We examine the collective description for the low-energy sector of $SU(N)$ matrix model, characterized by a factorized Hilbert space composed of a finite number of boxes and anti-boxes. This factorization leads us to examine the emergence of thermofield dynamics state in the low energy sector from a fine-tuned state. Our investigation of these matrix models elucidates a concrete mechanism for constructing the truncated algebra of accessible observables, thereby facilitating an understanding of black hole complementarity. In the context of the black hole information paradox, we discuss the origin of the island appearing inside the black hole and provide a reinterpretation of the recent proposal—the holography of information.