In this paper, we show how to carry out a relatively more realistic and complete reconstruction of supernova neutrino spectra in the future large liquid-scintillator detectors, by implementing the method of singular value decomposition with a proper regularization. For a core-collapse supernova at a distance of 10 kpc in the Milky Way, its ${\overline{\nu }}_e$ spectrum can be precisely determined from the inverse beta-decay process ${\overline{\nu }}_e+p\to e^{+}+n$, for which a 20 kiloton liquid-scintillator detector with the resolution similar to the Jiangmen Underground Neutrino Observatory may register more than 5000 events. We have to rely predominantly on the elastic neutrino-electron scattering $\nu +e^{-}\to \nu +e^{-}$ and the elastic neutrino-proton scattering $\nu +p\to \nu +p$ for the spectra of ${\nu }_e$ and ${\nu }_x$, where $\nu$ denotes collectively neutrinos and antineutrinos of all three flavors and ${\nu }_x$ for ${\nu }_{\mu }$ and ${\nu }_{\tau }$ as well as their antiparticles. To demonstrate the validity of our approach, we also attempt to reconstruct the neutrino spectra by using the time-integrated neutrino data from the latest numerical simulations of delayed neutrino-driven supernova explosions.

Extreme black holes have been argued to be unstable, in the sense that under linearized gravitational perturbations of the extreme Kerr spacetime the Weyl scalar ${\psi }_4$ blows up along their event horizons at very late advanced times. We show numerically, by solving the Teukolsky equation in $2+1\mathrm{D}$, that all algebraically independent curvature scalar polynomials approach limits that exist when advanced time along the event horizon approaches infinity. Therefore, the horizons of extreme black holes are stable against linearized gravitational perturbations. We argue that the divergence of ${\psi }_4$ is a consequence of the choice of a fixed tetrad, and that in a suitable dynamical tetrad all Weyl scalars, including ${\psi }_4$, approach their background extreme Kerr values. We make similar conclusions also for the case of scalar field perturbations of extreme Kerr.

We compute the shear viscosity of two-flavor QCD plasma in an external magnetic field in perturbative QCD at leading log order, assuming that the magnetic field is weak or soft: $eB\sim g^4\log (1/g)T^2$. We work in the assumption that the magnetic field is homogeneous and static, and the electrodynamics is nondynamical in a formal limit $e\to 0$ while $eB$ is kept fixed. We show that the shear viscosity takes a form $\eta =\overline{\eta }(\overline{B})T^3/(g^4\log (1/g))$ with a dimensionless function $\overline{\eta }(\overline{B})$ in terms of a dimensionless variable $\overline{B}=(eB)/(g^4\log (1/g)T^2)$. The variable $\overline{B}$ corresponds to the relative strength of the effect of cyclotron motions compared to the QCD collisions: $\overline{B}\sim l_{\mathrm{mfp}}/l_{\text{cyclo}}$. We provide a full numerical result for the scaled shear viscosity $\overline{\eta }(\overline{B})$.

Studying superpartner production together with a hard initial state radiation jet has been a useful strategy for searches of supersymmetry with a compressed spectrum at the LHC. In the case of the top squark (stop), the ratio of the missing transverse momentum from the lightest neutralinos and the initial state radiation momentum, defined as ${\overline{R}}_M$, turns out to be an effective variable to distinguish the signal from the backgrounds. It has helped to exclude the stop mass below 590 GeV along the top corridor where $m_{\tilde{t}}-m_{{\tilde{\chi }}_1^0}\approx m_t$. On the other hand, the current experimental limit is still rather weak in the $W$ corridor where $m_{\tilde{t}}-m_{{\tilde{\chi }}_1^0}\approx m_W+m_b$. In this work, we extend this strategy to the parameter region around the $W$ corridor by considering the one lepton final state. In this case, the kinematic constraints are insufficient to completely determine the neutrino momentum, which is required to calculate ${\overline{R}}_M$. However, the minimum value of ${\overline{R}}_M$ consistent with the kinematic constraints still provides a useful discriminating variable, allowing the exclusion reach of the stop mass to be extended to $\sim 550\mathrm{GeV}$ based on the current $36{\mathrm{fb}}^{-1}$ LHC data. The same method can also be applied to the chargino search with $m_{{\tilde{\chi }}_1^{\pm }}-m_{{\tilde{\chi }}_1^0}\approx m_W$ because the analysis does not rely on $b$ jets. If no excess is present in the current data, a chargino mass of 300 GeV along the $W$ corridor can be excluded, beyond the limit obtained from the multilepton search.

The idea that the Majorana neutrino should be identified as a Bogoliubov quasiparticle is applied to the seesaw mechanism for the three generations of neutrinos in the Standard Model. A relativistic analog of the Bogoliubov transformation in the present context is a $CP$-preserving canonical transformation but modifies charge conjugation properties in such a way that the C-noninvariant fermion number–violating term (condensate) is converted to a Dirac mass term. Puzzling aspects associated with the charge conjugation of chiral Weyl fermions are clarified.

A search for long-lived, massive particles predicted by many theories beyond the Standard Model is presented. The search targets final states with large missing transverse momentum and at least one high-mass displaced vertex with five or more tracks, and uses $32.8{\mathrm{fb}}^{-1}$ of $\sqrt{s}=13\mathrm{TeV}$ $pp$ collision data collected by the ATLAS detector at the LHC. The observed yield is consistent with the expected background. The results are used to extract 95% C.L. exclusion limits on the production of long-lived gluinos with masses up to 2.37 TeV and lifetimes of $\mathcal{O}({10}^{-2})-\mathcal{O}(10)\mathrm{ns}$ in a simplified model inspired by split supersymmetry.

Using a data sample of $(448.1\pm 2.9)\times {10}^6\psi (3686)$ events collected with the BESIII detector at the BEPCII collider, we present measurements of branching fractions for the decays ${\chi }_{cJ}\to {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-}$ and ${\mathrm{\Sigma }}^0{\overline{\mathrm{\Sigma }}}^0$. The decays ${\chi }_{c1,2}\to {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-}$ and ${\mathrm{\Sigma }}^0{\overline{\mathrm{\Sigma }}}^0$ are observed for the first time, and the branching fractions for ${\chi }_{c0}\to {\mathrm{\Sigma }}^{+}{\overline{\mathrm{\Sigma }}}^{-}$ and ${\mathrm{\Sigma }}^0{\overline{\mathrm{\Sigma }}}^0$ decays are measured with improved precision. The branching fraction ratios between the charged and neutral modes are consistent with the prediction of isospin symmetry.

The decay rate of the Bunch-Davies state of a massive scalar field in the expanding flat spatial sections of de Sitter space is determined by an analysis of the particle pair creation process in real time. The Feynman definition of particle and antiparticle Fourier mode solutions of the scalar wave equation and their adiabatic phase analytically continued to the complexified time domain show conclusively that the Bunch-Davies state is not the vacuum state at late times. The closely analogous creation of charged particle pairs in a uniform electric field is reviewed and Schwinger’s result for the vacuum decay rate is recovered by this same real time analysis. The vacuum decay rate in each case is also calculated by switching the background field on adiabatically, allowing it to act for a very long time, and then adiabatically switching it off again. In both the uniform electric field and de Sitter cases, the particles created while the field is switched on are verified to be real, in the sense that they persist in the final asymptotic flat zero-field region. In the de Sitter case, there is an interesting residual dependence of the rate on how the de Sitter phase is ended, indicating a greater sensitivity to spatial boundary conditions. The electric current of the created particles in the $E$-field case and their energy density and pressure in the de Sitter case are also computed, and the magnitude of their backreaction effects on the background field estimated. Possible consequences of the Hubble scale instability of the de Sitter vacuum for cosmology, vacuum dark energy, and the cosmological “constant” problem are discussed.

We report on a new open-source, user-friendly numerical relativity code package called $\mathrm{SENR}/\mathrm{NRPy}+$. Our code extends previous implementations of the BSSN reference-metric formulation to a much broader class of curvilinear coordinate systems, making it ideally suited to modeling physical configurations with approximate or exact symmetries. In the context of modeling black hole dynamics, it is orders of magnitude more efficient than other widely used open-source numerical relativity codes. $\mathrm{NRPy}+$ provides a Python-based interface in which equations are written in natural tensorial form and output at arbitrary finite difference order as highly efficient C code, putting complex tensorial equations at the scientist’s fingertips without the need for an expensive software license. SENR provides the algorithmic framework that combines the C codes generated by $\mathrm{NRPy}+$ into a functioning numerical relativity code. We validate against two other established, state-of-the-art codes, and achieve excellent agreement. For the first time—in the context of moving puncture black hole evolutions—we demonstrate nearly exponential convergence of constraint violation and gravitational waveform errors to zero as the order of spatial finite difference derivatives is increased, while fixing the numerical grids at moderate resolution in a singular coordinate system. Such behavior outside the horizons is remarkable, as numerical errors do not converge to zero near punctures, and all points along the polar axis are coordinate singularities. The formulation addresses such coordinate singularities via cell-centered grids and a simple change of basis that analytically regularizes tensor components with respect to the coordinates. Future plans include extending this formulation to allow dynamical coordinate grids and bispherical-like distribution of points to efficiently capture orbiting compact binary dynamics.

We present a model of holographic dark energy in which the infrared cutoff is determined by both the Ricci and the Gauss-Bonnet invariants. Such a construction has the significant advantage that the infrared cutoff, and consequently the holographic dark energy density, does not depend on the future or the past evolution of the universe, but only on its current features, and moreover it is determined by invariants, whose role is fundamental in gravitational theories. We extract analytical solutions for the behavior of the dark energy density and equation-of-state parameters as functions of the redshift. These reveal the usual thermal history of the universe, with the sequence of radiation, matter and dark energy epochs, resulting in the future to a complete dark energy domination. The corresponding dark energy equation-of-state parameter can lie in the quintessence or phantom regime, or experience the phantom-divide crossing during the cosmological evolution, and its asymptotic value can be quintessencelike, phantomlike, or be exactly equal to the cosmological-constant value. Finally, we extract the constraints on the model parameters that arise from big bang nucleosynthesis.

We further develop the description of redshift-space distortions within the effective field theory of large scale structures. First, we generalize the counterterms to include the effect of baryonic physics and primordial non-Gaussianity. Second, we evaluate the IR resummation of the dark matter power spectrum in redshift space. This requires us to identify a controlled approximation that makes the numerical evaluation straightforward and efficient. Third, we compare the predictions of the theory at one loop with the power spectrum from numerical simulations up to $\ell =6$. We find that the IR resummation allows us to correctly reproduce the baryon acoustic oscillation peak. The $k$ reach—or, equivalently, the precision for a given $k$—depends on additional counterterms that need to be matched to simulations. Since the nonlinear scale for the velocity is expected to be longer than the one for the overdensity, we consider a minimal and a nonminimal set of counterterms. The quality of our numerical data makes it hard to firmly establish the performance of the theory at high wave numbers. Within this limitation, we find that the theory at redshift $z=0.56$ and up to $\ell =2$ matches the data at the percent level approximately up to $k\sim 0.13h{\mathrm{Mpc}}^{-1}$ or $k\sim 0.18h{\mathrm{Mpc}}^{-1}$, depending on the number of counterterms used, with a potentially large improvement over former analytical techniques.

In this article, we consider the magnetic corrections to $\pi \text{−}\pi$ scattering lengths in the frame of the linear sigma model. For this, we consider all the one-loop corrections in the $s$, $t$, and $u$ channels, associated to the insertion of a Schwinger propagator for charged pions, working in the region of small values of the magnetic field. Our calculation relies on an appropriate expansion for the propagator. It turns out that the leading scattering length, $l=0$ in the $S$ channel, increases for an increasing value of the magnetic field, in the isospin $I=2$ case, whereas the opposite effect is found for the $I=0$ case. The isospin symmetry is valid because the insertion of the magnetic field occurs through the absolute value of the electric charges. The channel $I=1$ does not receive any corrections. These results, for the channels $I=0$ and $I=2$, are opposite with respect to the thermal corrections found previously in the literature.

We evaluate the induced value of Newton’s constant which would arise in QCD. The ingredients are modern lattice results, perturbation theory and the operator product expansion. The resulting shift in the Planck mass is positive. A scaled-up version of such a theory may be part of a quantum field theory treatment of gravity.

At present, the Boer-Mulders (BM) function for a given quark flavor is extracted from data on semi-inclusive deep inelastic scattering (SIDIS) using the simplifying assumption that it is proportional to the Sivers function for that flavor. In a recent paper, we suggested that the consistency of this assumption could be tested using information on so-called difference asymmetries i.e. the difference between the asymmetries in the production of particles and their antiparticles. In this paper, using the SIDIS COMPASS deuteron data on the $⟨\cos {\varphi }_h⟩$, $⟨\cos 2{\varphi }_h⟩$ and Sivers difference asymmetries, we carry out two independent consistency tests of the assumption of proportionality, but here applied to the sum of the valence-quark contributions. We find that such an assumption is compatible with the data. We also show that the proportionality assumptions made in the existing parametrizations of the BM functions are not compatible with our analysis, which suggests that the published results for the Boer-Mulders functions for individual flavors are unreliable. The $⟨\cos {\varphi }_h⟩$ and $⟨\cos 2{\varphi }_h⟩$ asymmetries receive contributions also from the, in principle, calculable Cahn effect. We succeed in extracting the Cahn contributions from experiment (we believe for the first time) and compare with their calculated values, with interesting implications.

The scale at which supersymmetry (SUSY) breaks ($m_s$) is still unknown. The present article, following a top-down approach, endeavors to study the effect of varying $m_s$ on the radiative stability of the observational parameters associated with the neutrino mixing. These parameters get additional contributions in the minimal supersymmetric model (MSSM). A variation in $m_s$ will influence the bounds for which the Standard Model (SM) and MSSM work and hence, will account for the different radiative contributions received from both sectors, respectively, while running the renormalization group equations (RGE). The present work establishes the invariance of the self complementarity relation among the three mixing angles, ${\theta }_{13}+{\theta }_{12}\approx {\theta }_{23}$ against the radiative evolution. A similar result concerning the mass ratio, $m_2:m_1$ is also found to be valid. In addition to varying $m_s$, the work incorporates a range of different seesaw (SS) scales and tries to see how the latter affects the parameters.

A search for electroweak production of supersymmetric particles in scenarios with compressed mass spectra in final states with two low-momentum leptons and missing transverse momentum is presented. This search uses proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015–2016, corresponding to $36.1{\mathrm{fb}}^{-1}$ of integrated luminosity at $\sqrt{s}=13\mathrm{TeV}$. Events with same-flavor pairs of electrons or muons with opposite electric charge are selected. The data are found to be consistent with the Standard Model prediction. Results are interpreted using simplified models of $R$-parity-conserving supersymmetry in which there is a small mass difference between the masses of the produced supersymmetric particles and the lightest neutralino. Exclusion limits at 95% confidence level are set on next-to-lightest neutralino masses of up to 145 GeV for Higgsino production and 175 GeV for wino production, and slepton masses of up to 190 GeV for pair production of sleptons. In the compressed mass regime, the exclusion limits extend down to mass splittings of 2.5 GeV for Higgsino production, 2 GeV for wino production, and 1 GeV for slepton production. The results are also interpreted in the context of a radiatively-driven natural supersymmetry model with nonuniversal Higgs boson masses.

We give an explicit toy qubit transport model for transferring information from the gravitational field of a black hole to the Hawking radiation by a continuous unitary transformation of the outgoing radiation and the black hole gravitational field. The model has no firewalls or other drama at the event horizon, and it avoids a counterargument that has been raised for subsystem transfer models as resolutions of the firewall paradox. Furthermore, it fits the set of six physical constraints that Giddings has proposed for models of black hole evaporation. It does utilize nonlocal qubits for the gravitational field but assumes that the radiation interacts locally with these nonlocal qubits, so in some sense the nonlocality is confined to the gravitational sector. Although the qubit model is too crude to be quantitatively correct for the detailed spectrum of Hawking radiation, it fits qualitatively with what is expected.

In this paper, we investigate the action growth in various backgrounds in Einstein-Maxwell-dilaton theory. We calculate the full time evolution of action growth in the anti–de Sitter dilaton black hole and find it approaches the late time bound from above. We investigate the black hole which is asymptotically Lifshitz and obtain its late time and full time behavior. We find the violation of Lloyd bound in the late time limit and show the full time behavior approaching the late time bound from above and exhibiting some new features for $z$ sufficiently large.

We extend the phenomenology of loop quantum cosmology (LQC) to second order in perturbations. Our motivation is twofold. On the one hand, since LQC predicts a cosmic bounce that takes place at the Planck scale, the second-order contributions could be large enough to jeopardize the validity of the perturbative expansion on which previous results rest. On the other hand, the upper bounds on primordial non-Gaussianity obtained by the Planck Collaboration are expected to play a significant role on explorations of the LQC phenomenology. We find that the bounce in LQC produces an enhancement of non-Gaussianity of several orders of magnitude, on length scales that were larger than the curvature radius at the bounce. Nonetheless, we find that one can still rely on the perturbative expansion to make predictions about primordial perturbations. We discuss the consequences of our results for LQC and its predictions for the cosmic microwave background.

In this work, we use the renormalization group method in the study of the behavior of a quartic fermionic self-interaction in a Gross-Neveu-Thirring model in $2+1$ dimensions, in the context of Hořava-Lifshitz theory. We show that if we include high derivatives in the spatial part of the free Lagrangian density for a critical exponent $z=2$ the model becomes renormalizable by power counting, thus improving the ultraviolet (UV) behavior of theory. We determine the renormalization group (RG) functions at one-loop order and we obtain the fixed points of effective beta function $(\overline{\beta })$. We find that it is asymptotically free for the case $\overline{\beta }<0$.