Fully depleted thick silicon skipper-charge-coupled devices (skipper CCDs) are an important technology to probe neutrino and light-dark-matter interactions due to their subelectron read-out noise. However, the successful search for rare neutrino or dark-matter events requires the signal and all backgrounds to be fully characterized. In particular, a measurement of the electron-hole pair creation energy below 150 eV and the Fano factor are necessary for characterizing the dark matter and neutrino signals. Moreover, photons from background radiation may Compton scatter in the silicon bulk, producing events that can mimic a dark matter or neutrino signal. We present a measurement of the Compton spectrum using a skipper CCD and a ${}^{241}\mathrm{Am}$ source. With these data, we estimate the electron-hole pair-creation energy to be $(3.71\pm 0.08)\mathrm{eV}$ at 130 K in the energy range between 99.3 eV and 150 eV. By measuring the widths of the steps at 99.3 eV and 150 eV in the Compton spectrum, we introduce a novel technique to measure the Fano factor, setting an upper limit of 0.31 at 90% C.L. These results prove the potential of skipper CCDs to characterize the Compton spectrum and to measure precisely the Fano factor and electron-hole pair creation energy below 150 eV.

We compute the pseudocomplexity of purification corresponding to the reduced transition matrices for free scalar field theories with an arbitrary dynamical exponent. We plot the behavior of complexity with various parameters of the theory under study and compare it with the complexity of purification of the reduced density matrices of the two states $|{\psi }_1⟩$ and $|{\psi }_2⟩$ that constitute the transition matrix. We first find the transition matrix by reducing to a small number (1 and 2) of degrees of freedom in lattice from a lattice system with many lattice points and then purify it by doubling the degrees of freedom (2 and 4 respectively) for this reduced system. This is a primary step towards the natural extension to the idea of the complexity of purification for reduced density matrices relevant for the studies related to postselection.

It has been argued that a self-interacting massive vector field is pathological due to a dynamical formation of a singular effective metric of the vector field, which is the onset of a gradient or ghost instability. We discuss that this singularity formation is not necessarily a fundamental problem but a breakdown of the effective field theory (EFT) description of the massive vector field. By using a model of ultraviolet (UV) completion of the massive vector field, we demonstrate that a Proca star, a self-gravitating condensate of the vector field, continues to exist even after the EFT suffers from a gradient instability without any pathology at UV, in which the EFT description is still valid and the gradient instability in EFT may be interpreted as a standard dynamical instability of a high-density boson star from the UV perspective. On the other hand, we find that the EFT description is broken before the ghost instability appears. This suggests that a heavy degree of freedom may be spontaneously excited to cure the pathology of the EFT as the EFT dynamically tends to approach the onset of the ghost instability.

We examine in greater detail the proposal that time is the conjugate of the constants of nature. Fundamentally distinct times are associated with different constants, a situation often found in “relational time” settings. We show how in regions dominated by a single constant the Hamiltonian constraint can be reframed as a Schrödinger equation in the corresponding time, solved in the connection representation by outgoing-only monochromatic plane waves moving in a “space” that generalizes the Chern-Simons functional (valid for the equation of state $w=-1$) for other $w$. We pay special attention to the issues of unitarity and the measure employed for the inner product. Normalizable superpositions can be built, including solitons, “light-rays” and coherent/squeezed states saturating a Heisenberg uncertainty relation between constants and their times. A healthy classical limit is obtained for factorizable coherent states, both in monofluid and multifluid situations. For the latter, we show how to deal with transition regions, where one is passing on the baton from one time to another, and investigate the fate of the subdominant clock. For this purpose minisuperspace is best seen as a dispersive medium, with packets moving with a group speed distinct from the phase speed. We show that the motion of the packets’ peaks reproduces the classical limit even during the transition periods, and for subdominant clocks once the transition is over. Deviations from the coherent/semiclassical limit are expected in these cases, however. The fact that we have recently transitioned from a decelerating to an accelerating Universe renders this proposal potentially testable, as explored elsewhere.

Gravitational wave science is dependent upon expensive numerical simulations, which provide the foundational understanding of binary merger radiation needed to interpret observations of massive binary black holes. The high cost of these simulations limits large-scale campaigns to explore the binary black hole parameter space. Surrogate models have been developed to efficiently interpolate between simulation results, but these models require a sufficiently comprehensive sample to train on. Acquisition functions can be used to identify points in the domain for simulation. We develop a new acquisition function which accounts for the cost of simulating new points. We show that when applied to a 3D domain of binary mass ratio and dimensionless nonprecessing spins, the accumulated cost of simulation is reduced by a factor of about 10.

Two novel classes of nonlinearly charged black hole (BH) solutions are introduced in the context of massive gravity theory, which are coupled to the logarithmic and exponential theories of nonlinear electrodynamics. The solutions can produce one-horizon, two-horizon, extreme, and naked singularity BHs with the massive Reissner-Nordström BHs’ asymptotic behavior. The BHs’ conserved and thermodynamic quantities are calculated under the influence of both massive gravitons and nonlinear electrodynamics. Through a Smarr-type mass formula, it is shown that these quantities satisfy the standard form of the thermodynamical first law. Thermal stability of the massive BHs is investigated using the canonical ensemble and geometrical methods, separately. The first- and second-order phase transition points, and the size of those BHs which remain locally stable, are determined. Then, the results of these alternative approaches are compared. By calculating the Gibbs free energies, global stability or Hawking-Page phase transition of the BHs is studied. The points at which the phase transition takes place and the conditions under which the BHs are globally stable are characterized. The critical behavior of the BHs is studied in the extended phase space by considering the thermodynamic pressure proportional to the cosmological constant.

Combining supernovae, baryon acoustic oscillations, and redshift-space distortions data from the next generation of (stage-IV) cosmological surveys, we aim to reconstruct the expansion history up to large redshifts using forward-modeling of $f_{\mathrm{DE}}(z)={\rho }_{\mathrm{DE}}(z)/{\rho }_{\mathrm{DE},0}$ with Gaussian processes (GP). In order to reconstruct cosmological quantities at high redshifts where few or no data are available, we adopt a new approach to GP which enforces the following minimal assumptions: (a) Our cosmology corresponds to a flat Friedman-Lemaître-Robertson-Walker universe; (b) An Einstein de Sitter (EdS) universe is obtained on large redshifts. This allows us to reconstruct the perturbations growth history from the reconstructed background expansion history. Assuming various DE models, we show the ability of our reconstruction method to differentiate them from $\mathrm{\Lambda }\mathrm{CDM}$ at $\gtrsim 2\sigma$.

Astrophysical observations of neutron stars have been widely used to infer the properties of the nuclear matter equation of state. Beside being a source of information on average properties of dense matter, the data provided by electromagnetic and gravitational wave (GW) facilities are reaching the accuracy needed to constrain, for the first time, the underlying nuclear dynamics. In this work, we assess the sensitivity of current and future neutron star observations to directly infer the strength of repulsive three-nucleon forces, which are key to determine the stiffness of the equation of state. Using a Bayesian approach, we focus on the constraints that can be derived on three-body interactions from binary neutron star mergers observed by second- and third-generations of gravitational wave interferometers. We consider both single and multiple observations. For current detectors at design sensitivity, the analysis suggests that only low mass systems, with large signal-to-noise ratios, allow one to reliably constrain the three-body forces. However, our results show that a single observation with a third-generation interferometer, such as the Einstein Telescope or Cosmic Explorer, will constrain the strength of the repulsive three-nucleon potential with exquisite accuracy, turning third-generation GW detectors into new laboratories to investigate the properties of nucleon interactions.

An excess of events of unknown origin at low energies below 1 keV has been observed in multiple low-threshold dark matter detectors. Understanding the origin of these events is of utmost importance, as this unidentified event rate currently overwhelms any potential new physics signal. Depending on the target material, nuclear recoil events at these energies may cause lattice defects, in which case a part of the true recoil energy is stored in the defect and not observed in the phonon detector. If the threshold for defect creation is sharp, this effect leads to a prominent feature in the observed recoil spectrum. Electronic recoils at low energies do not create defects and therefore the feature in the observed spectrum is not expected in that case. We propose to use the sharp defect creation threshold of diamond to test if the low-energy events are due to nuclear recoils. Based on simulated data we expect the nuclear recoil peak in the observed spectrum to be visible in diamond with a data set of $\sim 700$ events, potentially achievable with $\sim 0.1$ gram days of exposure.

Hadron-quark phase transition in neutron star cores is achieved in the present work with the help of the Maxwell construction. For this purpose, we employ six different and well-known hadronic models for the pure hadronic phase. The quark phase is described with the MIT bag model in which the density dependence of the bag pressure $B(\rho )$ is invoked for different asymptotic values ($B_{\mathrm{as}}$) of $B(\rho )$. The resulting hybrid star (HS) configurations exhibit twin star characteristics and distinct special points (SPs) on the mass-radius diagram of the HSs irrespective of the transition densities and the value of $B_{\mathrm{as}}$. We find that for any particular value of $B_{\mathrm{as}}$, the mass corresponding to SP ($M_{\mathrm{SP}}$) and the maximum mass ($M_{\max }$) of the HSs, obtained with different hadronic models, follow a nearly linear (fitted) relationship where the slope is independent of the value of $B_{\mathrm{as}}$. The $M_{\mathrm{SP}}-M_{\max }$ dependence of the HSs is found to be consistent with any hadronic equation of state (EoS) chosen to obtain the hybrid EoS, and thus, such relations can be considered as universal relations in the context of formation of SPs. A change in the value of $B_{\mathrm{as}}$ shifts the position of the fitted line in the $M_{\mathrm{SP}}-M_{\max }$ plane, with the linearity, however, retained.

We study scalar one-loop amplitudes in massive ${\varphi }^3$-theory within causal loop-tree duality. We derive a recurrence relation for the integrand of the amplitude. The integrand is by construction free of spurious singularities on H-surfaces. Taking renormalization and contour deformation into account, we obtain the (integrated) amplitude by Monte Carlo integration. We have checked up to seven points that our results agree with analytic results.

We derive the transport coefficients of second-order fluid dynamics with 14 dynamical moments using the method of moments and the Chapman-Enskog method in the relaxation-time approximation for the collision integral of the relativistic Boltzmann equation. Contrary to results previously reported in the literature, we find that the second-order transport coefficients derived using the two methods are in perfect agreement. Furthermore, we show that, unlike in the case of binary hard-sphere interactions, the diffusion-shear coupling coefficients ${\ell }_{V\pi }$, ${\lambda }_{V\pi }$, and ${\tau }_{V\pi }$ actually diverge in some approximations when the expansion order $N_{\ell }\to \infty$. Here we show how to circumvent such a problem in multiple ways, recovering the correct transport coefficients of second-order fluid dynamics with 14 dynamical moments. We also validate our results for the diffusion-shear coupling by comparison to a numerical solution of the Boltzmann equation for the propagation of sound waves in an ultrarelativistic ideal gas.

The gravitational form factors which are obtained from the matrix elements of the energy-momentum tensor provide us information about internal distributions of mass, energy, pressure, and shear. The Druck term is the least understood among all the gravitational form factors. In a light front quark-diquark model of a proton, we investigate the Druck form factor. Using Abel transformation, we evaluate the 3D distribution in the Breit frame from the 2D light front distributions. The results are compared with other models and lattice predictions.

If neutrinos get mass through the exchange of lepton mediators, as in seesaw schemes, the neutrino appearance probabilities in oscillation experiments are modified due to effective nonunitarity of the lepton mixing matrix. This also leads to new $CP$ phases and an ambiguity in underpinning the “conventional” phase of the three-neutrino paradigm. We study the $CP$ sensitivities of various setups based at the European Spallation Source neutrino super-beam (ESSnuSB) experiment in the presence of nonunitarity. We also examine its potential in constraining the associated new physics parameters. Moreover, we show how the combination of DUNE and ESSnuSB can help further improve the sensitivities on the nonunitarity parameters.

The isovector axial form factor of the nucleon plays a key role in interpreting data from long-baseline neutrino oscillation experiments. We perform a lattice-QCD based calculation of this form factor, introducing a new method to directly extract its $z$ expansion from lattice correlators. Our final parametrization of the form factor, which extends up to spacelike virtualities of $0.7{\mathrm{GeV}}^2$ with fully quantified uncertainties, agrees with previous lattice calculations but is significantly less steep than neutrino-deuterium scattering data suggests.

The charmless decay processes of $X(3872)$ provide us a good platform to study the nature and the decay mechanism of $X(3872)$. Based on a molecular nature of $X(3872)$ as a $\overline{D}{D}^{*}$ bound state, we have investigated the charmless decays $X(3872)\to VV$ and $VP$ via intermediate $D^{*}\overline{D}+\mathrm{c}.\mathrm{c}.$ meson loops, where $V$ and $P$ stand for light vector and pseudoscalar mesons, respectively. We discuss three cases, i.e., pure neutral components ($\theta =0$), isospin singlet ($\theta =\pi /4$) and neutral components dominant ($\theta =\pi /6$), where $\theta$ is a phase angle describing the proportion of neutral and charged constituents. The proportion of neutral and charged constituent has an influence on the decay widths of $X(3872)\to VV$ and $VP$. With the coupling constant of $X(3872)$ to the $\overline{D}{D}^{*}$ channel obtained under the molecule ansatz of $X(3872)$ resonance, the predicted decay widths of $X(3872)\to VV$ are about tens of keVs, while the decay width can reach a few hundreds of keVs for $X(3872)\to VP$. The dependence of these ratios between different decay modes of $X(3872)\to VV$ and $X(3872)\to VP$ to the mixing angle $\theta$ is also investigated. It is expected that the theoretical calculations here can be tested by future experiments.

We make a systematic calculation of the spectra and hadronic decays of the $D_s$ system in a coupled channel framework, where the unquenched effects are induced by the ${}^3{P}_0$ model. In the calculation, the wave functions are obtained by using a nonrelativistic potential model and are handled precisely with Gaussian expansion method. Even though the fitting mainly focuses on the spectrum, our model agrees well with the experiments on both the spectra and the hadronic decays, suggesting that the coupled channel effect could result in a reasonable and coherent description of the $D_s$ mesons. Based on the calculation, we give a detailed analysis on various aspects of the excited states, especially $D_{s0}^{*}(2317),D_{s1}(2460),D_{s1}(2536),D_{s1}^{*}(2860),D_{s0}(2590)$, and $D_{sJ}^{*}(3040)$. We also predict that $D_{s0}^{*}(2^3{P}_0)$ should be a $D^{*}{K}^{*}$ dominant molecule with mass 2894 MeV, which is only 5 MeV below the $D^{*}{K}^{*}$ threshold.

QCD jets provide one of the best avenues to extract information about the quark-gluon plasma produced in the aftermath of ultrarelativistic heavy-ion collisions. The structure of jets, determined by multiparticle quantum interference, is hard to tackle using perturbative methods. When jets evolve in a QCD medium this interference pattern is modified, adding another layer of complexity. By taking advantage of recent developments in quantum technologies, such effects might be better understood via direct quantum simulation of jet evolution. In this work, we introduce a precursor to such simulations. Based on the light-front Hamiltonian formalism, we construct a digital quantum circuit that tracks the evolution of a single hard probe in the presence of a stochastic color background. In terms of the jet quenching parameter $\widehat{q}$, the results obtained using classical simulators of ideal quantum computers agree with known analytical results. With this study, we hope to provide a baseline for future in-medium jet physics studies using quantum computers.

Production of $p\overline{p}$ and $n\overline{n}$ pairs in $e^{+}{e}^{-}$ annihilation near the threshold of the process is discussed with account for the new experimental data that appeared recently. Since a significant part of these new data was obtained at energies noticeably exceeding the threshold, we also take into account the form factor describing the amplitude of $N\overline{N}$ pair production at small distances. The effective optical potential, which describes a sharp dependence of the $N\overline{N}$ production cross sections near the threshold, consists of the central potential for $S$ and $D$ waves and the tensor potential. These potentials differ for states with isospin $I=0$ and $I=1$ of the $N\overline{N}$ pair. The optical potential describes well $N\overline{N}$ scattering phases, the cross sections of $p\overline{p}$ and $n\overline{n}$ production in $e^{+}{e}^{-}$ annihilation near the threshold, and the electromagnetic form factors $G_E$ and $G_M$ for protons and neutrons, as well as the cross sections of the processes $e^{+}{e}^{-}\to 6\pi$ and $e^{+}{e}^{-}\to K^{+}{K}^{-}{\pi }^{+}{\pi }^{-}$.

By analyzing $(448.1\pm 2.9)\times {10}^6\psi (3686)$ events collected with the BESIII detector operating at the BEPCII collider, the decays of ${\chi }_{cJ}\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }}\eta$ ($J=0$, 1, and 2) are observed for the first time with statistical significances of $13.9\sigma$, $6.7\sigma$, and $8.2\sigma$, respectively. The product branching fractions of $\psi (3686)\to \gamma {\chi }_{cJ}$ and ${\chi }_{cJ}\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }}\eta$ are measured. Dividing by the world averages of the branching fractions of $\psi (3686)\to \gamma {\chi }_{cJ}$, the branching fractions of ${\chi }_{cJ}\to \mathrm{\Lambda }\overline{\mathrm{\Lambda }}\eta$ decays are determined to be $(2.31\pm 0.30\pm 0.21)\times {10}^{-4}$, $(5.86\pm 1.38\pm 0.68)\times {10}^{-5}$, and $(1.05\pm 0.21\pm 0.15)\times {10}^{-4}$ for $J=0$, 1 and 2, respectively, where the first uncertainties are statistical and the second systematic.