We study the effects of a spatially homogenous magnetic field in Bianchi-I cosmological models. The cases of a pure magnetic field and two models with additional dust and a massless scalar field (stiff matter) are also considered. At the beginning of the cosmological evolution, i.e., in the neighborhood of the singularity, the Universe is described by one of Kasner’s solutions, and asymptotically by another Kasner solution when the volume of the Universe tends to infinity. The transition law between these two Kasner regimes is established, and shown to coincide with the analogous law for the empty Bianchi-II universe. The universe filled with dust and a magnetic field undergoes the process of isotropization, while the presence of a massless scalar field induces a modification of the relations between Kasner indices in the two asymptotic regimes. In all of these cases, we analyze the approach to the singularity in some detail and comment on the issue of the possible singularity crossing.

Massive neutrinos modify the expansion history of the universe and suppress the structure formation below their free streaming scale. Cosmic microwave background (CMB) observations at small angular scales can be used to constrain the total mass $\mathrm{\Sigma }{m}_{\nu }$ of the three neutrino flavors. However, at these scales, the CMB-measured $\mathrm{\Sigma }{m}_{\nu }$ is degenerate with $\tau$, the optical depth to reionization, which quantifies the damping of CMB anisotropies due to the scattering of CMB photons with free electrons along the line of sight. Here we revisit the idea to use 21-cm power spectrum observations to provide direct estimates for $\tau$. A joint analysis of CMB and 21-cm data can alleviate the $\tau -\mathrm{\Sigma }{m}_{\nu }$ degeneracy, making it possible to measure $\mathrm{\Sigma }{m}_{\nu }$ with unprecedented precision. Forecasting for the upcoming Hydrogen Epoch of Reionization Array (HERA), we find that a $\lesssim \mathcal{O}(10\%)$ measurement of $\tau$ is achievable, which would enable a $\gtrsim 5\sigma$ measurement of $\mathrm{\Sigma }{m}_{\nu }=60[\mathrm{meV}]$, for any astrophysics model that we considered. Precise estimates of $\tau$ also help reduce uncertainties in other cosmological parameters, such as $A_s$, the amplitude of the primordial scalar fluctuations power spectrum.

Dark matter halos of dwarf spheroidal galaxies (dSphs) play important roles in dark matter detection. Generally we estimate the halo profile using a kinematical equation of dSphs but the halo profile has a large uncertainty because we have only a limited number of kinematical datasets. In this paper, we utilize cosmological models of dark matter subhalos to obtain better constraints on halo profile of dSphs. The constraints are realized as two cosmological priors: satellite prior, based on a semianalytic model of the accretion history of subhalos and their tidal stripping effect, and stellar-to-halo mass relation prior, which estimates halo mass of a galaxy from its stellar mass using empirical correlations. In addition, we adopt a radial dependent likelihood function by considering the velocity dispersion profile, which allows us to mitigate the parameter degeneracy in the previous analysis using a radial independent likelihood function with averaged dispersion. Using these priors, we estimate the squared dark matter density integrated over the region of interest (so-called $J$ factor) of eight classical and 27 ultrafaint dSphs. Our method significantly decreases the uncertainty of $J$ factors (up to about 20%) compared to the previous radial independent analysis. We confirm the model dependence of $J$-factor estimates by evaluating Bayes factors of different model setups and find that the estimates are still stable even when assuming different cosmological models.

Measuring the radio emission from cosmic-ray particle cascades has proven to be a very efficient method to determine their properties such as the mass composition. Efficient modeling of the radio emission from air showers is crucial in order to extract the cosmic-ray physics parameters from the measured radio emission. MGMR3D is a fast semianalytic code that calculates the complete radio footprint, i.e., intensity, polarization, and pulse shapes, for a parametrized shower-current density and can be used in a chi-square optimization to fit a given radio data. It is many orders of magnitude faster than its Monte Carlo counterparts. We provide a detailed comparative study of MGMR3D to Monte Carlo simulations, where, with improved parametrizations, the shower maximum $X_{\max }$ is found to have very strong agreement with a small dependency on the incoming zenith angle of the shower. Another interesting feature we observe with MGMR3D is sensitivity to the shape of the longitudinal profile in addition to $X_{\max }$. This is achieved by probing the distinguishable radio footprint produced by a shower having a different longitudinal profile than usual. Furthermore, for the first time, we show the results of reconstructing shower parameters for Low-Frequency Array data using MGMR3D, and obtaining a $X_{\max }$ resolution of $22\mathrm{g}/{\mathrm{cm}}^2$ and energy resolution of 19%.

We return to interpreting the historical SN 1987A neutrino data from a modern perspective. To this end, we construct a suite of spherically symmetric supernova models with the prometheus-vertex code, using four different equations of state and five choices of final baryonic neutron-star (NS) mass in the $1.36–1.93M_{\odot }$ range. Our models include muons and proto-neutron star (PNS) convection by a mixing-length approximation. The time-integrated signals of our $1.44M_{\odot }$ models agree reasonably well with the combined data of the four relevant experiments, IMB, Kam-II, BUST, and LSD, but the high-threshold IMB detector alone favors a NS mass of $1.7–1.8M_{\odot }$, whereas Kam-II alone prefers a mass around $1.4M_{\odot }$. The cumulative energy distributions in these two detectors are well-matched by models for such NS masses, and the previous tension between predicted mean neutrino energies and the combined measurements is gone, with and without flavor swap. Generally, our predicted signals do not strongly depend on assumptions about flavor mixing, because the PNS flux spectra depend only weakly on antineutrino flavor. While our models show compatibility with the events detected during the first seconds, PNS convection and nucleon correlations in the neutrino opacities lead to short PNS cooling times of 5–9 s, in conflict with the late-event bunches in Kam-II and BUST after 8–9 s, which are also difficult to explain by background. Speculative interpretations include the onset of fallback of transiently ejected material onto the NS, a late phase transition in the nuclear medium, e.g., from hadronic to quark matter, or other effects that add to the standard PNS cooling emission and either stretch the signal or provide a late source of energy. More research, including systematic 3D simulations, is needed to assess these open issues.

We simulate the time evolution of collective neutrino oscillations in two-flavor settings on a quantum computer. We explore the generalization of Trotter-Suzuki approximation to time-dependent Hamiltonian dynamics. The trotterization steps are further optimized using the Cartan decomposition of two-qubit unitary gates $U\in SU(4)$ in the minimum number of controlled-NOT (CNOT) gates making the algorithm more resilient to the hardware noise. A more efficient hybrid quantum-classical algorithm is also explored to solve the problem on noisy intermediate-scale quantum devices.

The collisionless Boltzmann equation, also called free-streaming, is a convenient approximation. It is rather simple to implement numerically, and it is effective at reducing the irregularities of rough initial conditions. It can be obtained as a small $\hslash$ limit from a free scalar quantum field, namely, by neglecting the ${\hslash }^2$ term in the dynamical evolution of the Wigner distribution, the quantum precursor of the distribution function. In this work, the general form for the exact solutions of the Wigner distribution is presented, for a scalar field undergoing a ($1+1$)-dimensional expansion, namely, with the symmetry constraints of rotation and translation invariance in the transverse plane. It is very different from the (on-shell) free-streaming of classical particles. It is shown how to recognize the classical $\hslash \to 0$ limit from the general form. The numerical analysis for a specific example shows very large quantum corrections to the classical free-streaming.

Supersymmetric models with low electroweak fine-tuning are expected to be more prevalent on the string landscape than fine-tuned models. We assume a fertile patch of landscape vacua containing the minimal supersymmetric standard model as low energy/weak scale effective field theory. Then, a statistical pull by the landscape to large soft terms is balanced by the requirement of a derived value of the weak scale which is not too far from its measured value in our Universe. Such models are characterized by light Higgsinos in the few hundred GeV range whilst top squarks are in the 1–2.5 TeV range with large trilinear soft terms which helps to push $m_h\sim 125\mathrm{GeV}$. Other sparticles are generally beyond current LHC reach and the $\mathrm{BR}(b\to s\gamma )$ branching fraction is nearly equal to its standard model value. The light top-squarks decay comparably via ${\tilde{t}}_1\to b{\tilde{\chi }}_1^{+}$ and ${\tilde{t}}_1\to t{\tilde{\chi }}_{1,2}^0$ yielding mixed final states of $b\overline{b}+{\cancel{E}}_T$, $t\overline{b}/\overline{t}b+{\cancel{E}}_T$, and $t\overline{t}+{\cancel{E}}_T$. We evaluate prospects for top squark discovery at high-luminosity LHC for the well-motivated case of natural SUSY from the landscape. We find for high luminosity LHC a $5\sigma$ reach out to $m_{{\tilde{t}}_1}\sim 1.65\mathrm{TeV}$ and a 95% CL exclusion reach to $m_{{\tilde{t}}_1}\sim 1.95\mathrm{TeV}$. These reaches cover most (but not all) of the allowed stringy natural parameter space.

The MUSE experiment at Paul Scherrer Institute will perform the first measurement of low-energy muon-proton elastic scattering (muon lab momenta 115–210 MeV) with the aim of determining the proton charge radius. We study the prospects for the proton radius extraction using the theoretical framework of dispersively improved chiral effective field theory ($\mathrm{DI}\chi \mathrm{EFT}$). It connects the proton radii with the finite-$Q^2$ behavior of the form factors through complex analyticity and enables the use of data up to $Q^2\sim 0.1{\mathrm{GeV}}^2$ for radius extraction. We quantify the sensitivity of the $\mu p$ cross section to the proton charge radius, the theoretical uncertainty of the cross section predictions, and the size of two-photon exchange corrections. We find that the optimal kinematics for radius extraction at MUSE is at momenta 210 MeV and $Q^2\sim 0.05–0.08{\mathrm{GeV}}^2$. We compare the performance of electron and muon scattering in the same kinematics. As a by-product, we obtain explicit predictions for the $\mu p$ and $ep$ cross sections at MUSE as functions of the assumed value of the proton radius.

We perform a theoretical analysis of the semileptonic decays ${\eta }^{(\prime )}\to {\pi }^0{\ell }^{+}{\ell }^{-}$ and ${\eta }^{\prime }\to \eta {\ell }^{+}{\ell }^{-}$, where $\ell =e$, $\mu$, via a charge-conjugation-conserving two-photon mechanism. The underlying form factors are modeled using vector-meson dominance, phenomenological input, and U(3) flavor symmetry. We consider both a monopole and a dipole model, the latter tailored such that the expected high-energy behavior is ensured. Furthermore, we benchmark the effect of $S$-wave rescattering contributions to the decays. We infer significant effects of the form factors neglected in the literature so far, still finding branching ratios of the various decays well below the current experimental upper limits.

The nucleon axial-vector coupling constant $g_A$ is studied in the presence of an external magnetic field, and in dense nuclear environments, to emulate nuclear matter in magnetars. For this purpose we use QCD finite energy sum rules for two-current and three-current correlators, the former involving nucleon-nucleon correlators and the latter involving proton-axial-neutron currents. As a result, the axial-vector coupling constant decreases both with baryon density as well as with magnetic field. The axial-vector coupling evaluated with baryon density near the nuclear density ${\rho }_0$ leads to $g_A^{*}\approx 0.92$. In the presence of magnetic fields $g_A$ decreases in general, but $g_A^{*}$ does not show significant changes.

We perform a blind search for particle signals in the XENON1T dark matter detector that occur close in time to gravitational-wave signals in the LIGO and Virgo observatories. No particle signal is observed in the nuclear recoil and electronic recoil channels within $\pm 500$ seconds of observations of the gravitational-wave signals GW170104, GW170729, GW170817, GW170818, and GW170823. We use this null result to constrain monoenergetic neutrinos and axion-like particles emitted in the closest coalescence GW170817, a binary neutron star merger. We set new upper limits on the fluence (time-integrated flux) of coincident neutrinos down to 17 keV at the 90% confidence level. Furthermore, we constrain the product of the coincident fluence and cross section of axion-like particles to be less than ${10}^{-29}{\mathrm{cm}}^2/{\mathrm{cm}}^2$ in the [5.5–210] keV energy range at the 90% confidence level.

Simulation is crucial for all aspects of collider data analysis, but the available computing budget in the High Luminosity LHC era will be severely constrained. Generative machine learning models may act as surrogates to replace physics-based full simulation of particle detectors, and diffusion models have recently emerged as the state of the art for other generative tasks. We introduce CaloDiffusion, a denoising diffusion model trained on the public CaloChallenge datasets to generate calorimeter showers. Our algorithm employs 3D cylindrical convolutions, which take advantage of symmetries of the underlying data representation. To handle irregular detector geometries, we augment the diffusion model with a new geometry latent mapping (GLaM) layer to learn forward and reverse transformations to a regular geometry that is suitable for cylindrical convolutions. The showers generated by our approach are nearly indistinguishable from the full simulation, as measured by several different metrics.

We revisit the entanglement of a Schwinger pair created by external fields of arbitrary strength, using a holographic dual description of QCD. When external fields are strong in comparison to the string tension, the entanglement is geometrically tied to the Einstein-Rosen (ER) bridge in the bulk, and disappears when the pair production is not exponentially suppressed at the boundary. For moderate external fields, the entanglement is shown to follow from the geometrical interplay between the position of the ER bridge and the confining wall in the bulk. We clarify the physical nature of quantum entanglement in pair production, and connect it to the entropy of entanglement between the left- and right-moving fermions. In particular, we clarify the effect of real radiation off the produced particles on quantum entanglement of the pair.

Following previous work by one of the authors [M. V. Altaisky, Unifying renormalization group and the continuous wavelet transform, Phys. Rev. D 93, 105043 (2016).], we develop a new approach to the renormalization group, where the effective action functional ${\mathrm{\Gamma }}_A[\varphi ]$ is a sum of all fluctuations of scales from the size of the system $L$ down to the scale of observation $A$. It is shown that the renormalization flow equation of the type $\frac{\partial {\mathrm{\Gamma }}_A}{\partial \ln A}=-Y(A)$ is a limiting case of such consideration, when the running coupling constant is assumed to be a differentiable function of scale. In this approximation, the running coupling constant, calculated at one-loop level, suffers from the Landau pole. In general, when the scale-dependent coupling constant is a nondifferentiable function of scale, the Feynman loop expansion results in a difference equation. This keeps the coupling constant finite for any finite value of scale $A$. As an example, we consider Euclidean ${\varphi }^4$ field theory.

Carrollian field theories at the classical level possess an infinite number of space-time symmetries, namely the supertranslations. In this article, we inquire whether these symmetries for interacting Carrollian scalar field theory survive in the presence of quantum effects. For interactions polynomial in the field, the answer is in the affirmative. We also study a renormalization group flow particularly tailored to respect the manifest Carroll invariance and analyze the consequences of introducing Carroll-breaking deformations. The renormalization group flow, with perturbative loop-level effects taken into account, indicates a new fixed point apart from the Gaussian ones.

Landau’s work on the singularities of Feynman diagrams suggests that they can only be of three types: either poles, logarithmic divergences, or the roots of quadratic polynomials. On the other hand, many Feynman integrals exist whose singularities involve arbitrarily higher-order polynomial roots. We investigate this apparent paradox using concrete examples involving cube roots and roots of a degree-eight polynomial in four dimensions and roots of a degree-six polynomial in two dimensions and suggest that these higher-order singularities can only be approached via kinematic limits of higher codimension than one, thus evading Landau’s argument.

Superconducting cavities can operate analogously to Weber bar detectors of gravitational waves, converting mechanical to electromagnetic energy. The significantly reduced electromagnetic noise results in increased sensitivity to high-frequency signals well outside the bandwidth of the lowest mechanical resonance. In this work, we revisit such signals of gravitational waves and demonstrate that a setup similar to the existing MAGO prototype, operating in a scanning or broadband manner, could have sensitivity to strains of $\sim {10}^{-22}-{10}^{-18}$ for frequencies of $\sim 10\mathrm{kHz}–1\mathrm{GHz}$.

The Indian Consortium of Cosmologists has proposed a cosmic microwave background (CMB) space mission, Exploring Cosmic History and Origin ($ECHO$). A major scientific goal of the mission is to detect the primordial $B$-mode signal of CMB polarization. The detection of the targeted signal is very challenging as it is deeply buried under the dominant astrophysical foreground emissions of the thermal dust and the Galactic synchrotron. To facilitate the adequate subtraction of thermal dust, the instrument design of $ECHO$ has included nine dust-dominated high-frequency bands over the frequency range 220–850 GHz. In this work, we closely reexamine the utility of the high-frequency $ECHO$ bands in foreground subtraction using the Needlet Internal Linear Combination component separation method. We consider three dust models: a physical dust model, a dust spectral energy distribution (SED) with a single modified black body (MBB) emission law and a multilayer dust model with frequency-frequency decorrelation. We consider eleven $ECHO$ bands in the 28–190 GHz range as our baseline configuration and investigate the changes in the level foreground and noise residuals as subsequent dust-dominated high-frequency bands are added. We find that adding the high-frequency bands leads to a consistent decrease in the level of residual foreground and noise, and the sensitivity of $r$ measurement improves. Most of the reduction in both residual levels and enhancement in the sensitivity is achieved in the 28–600 GHz frequency range. Negligible change in residual levels is seen by extending the frequency range from 600 GHz to 850 GHz. We find that extending the $ECHO$ frequency bands from 190 GHz to 340 GHz leads to a 40%–50% reduction in the foreground and noise residual levels in the recovered CMB map. Correspondingly the sensitivity of $ECHO$ toward $r$ also improves by a similar amount. Furthermore, incorporating higher frequencies up to 600 GHz yields an additional reduction of 12%–15% in the residual levels and uncertainty on $r$. However, extending observations up to the 850 GHz frequency band only leads to a marginal improvement in sensitivity, ranging from 3%–7%.

While most scintillation-based dark matter experiments search for weakly interacting massive particles (WIMPs), a sub-GeV WIMP-like particle may also be detectable in these experiments. While dark matter of this type and scale would not leave appreciable nuclear recoil signals, it may instead induce ionization of atomic electrons. Accurate modeling of the atomic wave functions is key to investigating this possibility, with incorrect treatment leading to a large suppression in the atomic excitation factors. We have calculated these atomic factors for argon, krypton, and xenon and present the tabulated results for use with a range of dark matter models. This is made possible by the separability of the atomic and dark matter form factor, allowing the atomic factors to be calculated for general couplings; we include tables for vector, scalar, pseudovector, and pseudoscalar electron couplings. Additionally, we calculate electron-impact total ionization cross sections for xenon using the tabulated results as a test of accuracy. Lastly, we provide an example calculation of the event rate for dark matter scattering on electrons in XENON1T and show that these calculations depend heavily on how the low-energy response of the detector is modeled.