The Schrödinger-Newton equation is a proposed model to explain the localization of macroscopic particles by suppressing quantum dispersion with the particle’s own gravitational attraction. On cosmic scales, however, dark energy also acts repulsively, as witnessed by the accelerating rate of universal expansion. Here, we introduce the effects of dark energy in the form of a cosmological constant $\mathrm{\Lambda }$, that drives the late-time acceleration of the Universe, into the Schrödinger-Newton approach. We then ask in which regime dark energy dominates both canonical quantum diffusion and gravitational self-attraction. It turns out that this happens for sufficiently delocalized objects with an arbitrary mass and that there exists a minimal delocalization width of about 67 m. While extremely macroscopic from a quantum perspective, the value is in principle accessible to laboratories on Earth. Hence, we analyze, numerically, how the dynamics of an initially spherical Gaussian wave packet is modified in the presence of $\mathrm{\Lambda }>0$. A notable feature is the gravitational collapse of part of the wave packet, in the core region close to the center of mass, accompanied by the accelerated expansion of the more distant shell surrounding it. The order of magnitude of the distance separating collapse from expansion matches analytical estimates of the classical turnaround radius for a spherically symmetric body in the presence of dark energy. However, the time required to observe these modifications is astronomical. They can potentially be measured only in physical systems simulating a high effective cosmological constant, or, possibly, via their effects on the inflationary universe.

In order to investigate the impact of collective neutrino oscillations (CNOs) on the neutrino signal from a nearby supernova, we perform three-flavor neutrino oscillation simulations employing the multiangle effect. The background hydrodynamic model is based on the neutrino hydrodynamic simulation of a $8.8M_{\odot }$ progenitor star. We find that CNO commences after some 100 ms post bounce. Before this, CNO is suppressed by matter-induced decoherence. In the inverted mass hierarchy, the spectrum of ${\overline{\nu }}_e$ becomes softer after the onset of CNO. To evaluate the detectability of this modification, we define a hardness ratio between the number of high energy neutrino events and low energy neutrino events adopting a fixed critical energy. We show that Hyper-Kamiokande (HK) can distinguish the effect of CNO for supernova distances out to $\sim 10\mathrm{kpc}$. On the other hand, for the normal mass hierarchy, the spectrum of ${\nu }_e$ becomes softer after the onset of CNO, and we show that DUNE can distinguish this feature for supernova distances out to $\sim 10\mathrm{kpc}$. More work is necessary to optimize the best value of critical energy for maximum sensitivity. We also show that if the spectrum of ${\overline{\nu }}_e$ in HK becomes softer due to CNO, the spectrum of ${\nu }_e$ in DUNE becomes harder, and vice versa. These synergistic observations in ${\overline{\nu }}_e$ and ${\nu }_e$, by HK and DUNE, respectively, will be an intriguing opportunity to test the occurrence of CNO.

How to represent a jet is at the core of machine learning on jet physics. Inspired by the notion of point clouds, we propose a new approach that considers a jet as an unordered set of its constituent particles, effectively a “particle cloud.” Such a particle cloud representation of jets is efficient in incorporating raw information of jets and also explicitly respects the permutation symmetry. Based on the particle cloud representation, we propose ParticleNet, a customized neural network architecture using Dynamic Graph Convolutional Neural Network for jet tagging problems. The ParticleNet architecture achieves state-of-the-art performance on two representative jet tagging benchmarks and is improved significantly over existing methods.

We study spin oscillations of neutrinos gravitationally scattered off a nonrotating black hole (BH). We derive the transition and survival probabilities of spin oscillations in quadratures when neutrinos interact with BHs only. The dependence of the probabilities on the impact parameter is analyzed. Then, we obtain the effective Schrödinger equation for spin oscillations in neutrino scattering off BHs surrounded by background matter. This equation is solved numerically in the case of a supermassive BH with a realistic accretion disk. We find that the observed neutrino fluxes can be reduced almost 20% because of spin oscillations when neutrinos experience gravitational scattering. The neutrino interaction with an accretion disk results in the additional asymmetry in the intensities of outgoing fluxes depending on the neutrino trajectory.

Gildener-Weinberg (GW) models of electroweak symmetry breaking are especially interesting because the low mass and nearly Standard Model couplings of the 125 GeV Higgs boson $H$ are protected by approximate scale symmetry. Another important but so far underappreciated feature of these models is that a sum rule bounds the masses of the new charged and neutral Higgs bosons appearing in all these models to be below about 500 GeV. Therefore, they are within reach of LHC data currently or soon to be in hand. Also so far unnoticed of these models, certain cubic and quartic Higgs scalar couplings vanish at the classical level. This is due to spontaneous breaking of the scale symmetry. These couplings become nonzero from explicit scale breaking in the Coleman-Weinberg loop expansion of the effective potential. In a two-Higgs doublet GW model, we calculate ${\lambda }_{HHH}\simeq 2({\lambda }_{HHH}{)}_{\mathrm{SM}}=64\mathrm{GeV}$. This corresponds to $\sigma (pp\to HH)\cong 15–20\mathrm{fb}$, its minimum value for $\sqrt{s}=13–14\mathrm{TeV}$ at the LHC. It will require at least the 27 TeV HE-LHC to observe this cross section. We also find ${\lambda }_{HHHH}\simeq 4({\lambda }_{HHHH}{)}_{\mathrm{SM}}=0.129$, whose observation in $pp\to HHH$ requires a 100 TeV collider. Because of the above-mentioned sum rule, these results apply to all GW models. In view of this unpromising forecast, we stress that LHC searches for the new relatively light Higgs bosons of GW models are by far the surest way to test them in this decade.

It is known that a five-dimensional free vector field $A_M$ cannot be localized on Randall-Sundrum (RS)-like thick branes—namely, the thick branes embedded in asymptotic anti–de Sitter spacetime. To localize a vector field on the RS-like thick brane, an extra coupling term should be introduced. We generalize the geometrical coupling mechanism by adding two mass terms ($\alpha R{g}^{MN}{A}_M{A}_N+\beta R^{MN}{A}_M{A}_N$) to the action. We decompose the fundamental vector field $A_M$ into three parts: transverse vector part ${\widehat{A}}_{\mu }$ and scalar parts $\varphi$ and $A_5$. Then we find that the transverse vector part ${\widehat{A}}_{\mu }$ decouples from the scalar parts. To eliminate the tachyonic modes of ${\widehat{A}}_{\mu }$, the two coupling parameters $\alpha$ and $\beta$ should satisfy a relation. Combining the restricted condition, we can get a combination parameter as $\gamma =\frac{3}{2}\pm \sqrt{1+12\alpha }$. Only if $\gamma >1/2$ can the zero mode of ${\widehat{A}}_{\mu }$ be localized on the RS-like thick brane. We also investigate the resonant character of the vector part ${\widehat{A}}_{\mu }$ for a general RS-like thick brane with a warp factor $A(z)=-\ln (1+k^2{z}^2)/2$ by choosing the relative probability method. The results show that the massive resonant Kaluza-Klein modes can exist only for $\gamma >3$. The number of resonant Kaluza-Klein states increases with the combination parameter $\gamma$, and the lifetime of the first resonant state can be as long as our Universe’s. This indicates that the vector resonances might be considered one of the candidates of dark matter. Combining the conditions of experimental observations, the constraint shows that the parameter $k$ has a lower limit with $k\gtrsim {10}^{-17}\mathrm{eV}$, the combination parameter $\gamma$ should be greater than 57, and, accordingly, the mass of the first resonant state should satisfy $m_1\gtrsim {10}^{-15}\mathrm{eV}$.

We propose a new method to determine the spatially or impact-parameter dependent nuclear parton distribution functions (nPDFs) using the double parton scattering (DPS) processes in high-energy heavy-ion (proton-nucleus and nucleus-nucleus) collisions. We derive a simple generic DPS formula in nuclear collisions by accommodating both the nuclear collision geometry and the spatially dependent nuclear modification effect, under the assumption that the impact-parameter dependence of nPDFs is only related to the nuclear thickness function. While the geometric effect is widely adopted, the impact of the spatially dependent nuclear modification on DPS cross sections has been overlooked so far, which can, however, be significant when the initial nuclear modification is large. In turn, the DPS cross sections in heavy-ion collisions can provide useful information on the spatial dependence of nPDFs. They can be, in general, obtained in minimum-bias nuclear collisions, featuring the virtue of independence of Glauber modeling.

In this paper, we investigate the inclusive diffractive hadroproduction for ${\eta }_{\mathrm{c}}$ and ${\eta }_{\mathrm{b}}$ at the Large Hadron Collider (LHC) energies. Based on the nonrelativistic QCD factorization formalism and the resolved-Pomeron model for the quarkonium production mechanism, we estimate the rapidity, the momentum fraction loss dependence of the cross section. We give prediction ratios for single and central diffractive processes with respect to the nondiffractive process. These inclusive processes are sensitive to the gluon content of Pomeron for small $x$ and Reggeon for large $x$, which is useful to study small and large-$x$ physics and good to test different mechanisms for ${\eta }_{\mathrm{c}}$ and ${\eta }_{\mathrm{b}}$ production at the LHC. They also serve as the background to related exclusive processes; thus, they should be predicted. Our results demonstrate that the Reggeon contribution of diffractive processes can be sizable, even sometimes dominant over Pomeron, and that its study can be useful to better constrain the Reggeon parton content. The experimental study of Reggeon can be carried out in certain kinematic windows.

The effective restoration of the $U_A(1)$ symmetry is revisited by implementing the functional renormalization group approach combined with the $2+1$ flavor Polyakov-loop quark-meson model. A temperature-dependent ’t Hooft term is taken to imitate the restoration of the $U_A(1)$ symmetry. Order parameters, meson spectrum and mixing angles, especially the pressure, the entropy density, and the speed of sound of the system are calculated to explore the effects of different $U_A(1)$ symmetry restoration patterns. We show then that the temperature for the restoration of the $U_A(1)$ symmetry is much higher than that for the chiral symmetry $S{U}_A(3)$.

Recently, a coherent picture of the quantum mechanics of an evaporating black hole has been presented which reconciles unitarity with the predictions of the equivalence principle. The thermal nature of a black hole as viewed in a distant reference frame arises from entanglement between the hard and soft modes generated by the chaotic dynamics at the string scale. In this paper, we elaborate on this picture, particularly emphasizing the importance of the chaotic nature of the string (UV) dynamics across all low-energy species in generating large (IR) spacetime behind the horizon. Implications of this UV/IR relation include $O(1)$ breaking of global symmetries at the string scale and a self-repair mechanism of black holes restoring the smoothness of their horizons. We also generalize the framework to other systems, including Rindler, de Sitter, and asymptotically flat spacetimes, and find a consistent picture in each case. Finally, we discuss the origin of the particular construction adopted in describing the black hole interior as well as the outside of a de Sitter horizon. We argue that the construction is selected by the quantum-to-classical transition, in particular, the applicability of the Born rule in a quantum mechanical world.

We find exact finite temperature solutions to $d=5$ Einstein-dilaton gravity with black branes and a Randall-Sundrum 3-brane. We show that there exists a unique generating superpotential for these models. The location of the black brane and the associated Hawking temperature depend on the value of the 3-brane tension, while other parameters are held fixed. The thermodynamics of these solutions are presented, from which we show that the entropy satisfies $S<\mathrm{Vol}({\mathbb{R}}^3)/4G_5$. We demonstrate that in a certain limit the gauge dual of this theory effectively reduces to $\mathcal{N}=4$ Super Yang-Mills at finite temperature on $S^1\times {\mathbb{R}}^3$.

We consider a collapsing shell of matter to form the Hayward black hole and investigate semiclassically quantum radiation from the shell. Using the Israel’s formulation, we obtain the mass relation between the collapsing shell and the Hayward black hole. By using the functional Schrödinger formulation for the massless quantum radiation, the evolution of a vacuum state for a scalar field is shown to be unitary. We find that the number of quanta at a low frequency decreases for a large length parameter characterizing the Hayward black hole. Moreover, in the limit of low frequency, the Hawking temperature can be read off from the occupation number of excited states when the shell approaches its own horizon.

For any quantum algorithm given by a path in the space of unitary operators we define the computational complexity as the typical computational time associated with the path. This time is defined using a quantum time estimator associated with the path. This quantum time estimator is fully characterized by the Lyapunov generator of the path and the corresponding quantum Fisher information. The computational metric associated with this definition of computational complexity leads to a natural characterization of cost factors on the Lie algebra generators. Operator complexity growth in time is analyzed from this perspective leading to a simple characterization of the Lyapunov exponent in the case of chaotic Hamiltonians. The connection between complexity and entropy is expressed using the relation between quantum Fisher information about quantum time estimation and von Neumann entropy. This relation suggests a natural bound on computational complexity that generalizes the standard time energy quantum uncertainty. The connection between Lyapunov and modular Hamiltonian is briefly discussed. In the case of theories with holographic duals and for those reduced density matrix defined by tracing over a bounded region of the bulk, quantum estimation theory is crucial to estimate quantum mechanically the geometry of the tracing region. It is suggested that the corresponding quantum Fisher information associated with this estimation problem is at the root of the holographic bulk geometry.

We investigate the effects of vacuum polarization on vacuum static spherically symmetric spacetimes. We start from the Polyakov approximation to the renormalized stress-energy tensor (RSET) of a minimally coupled massless scalar field. This RSET is not regular at $r=0$, so we define a regularized version of the Polyakov RSET. Using this regularized RSET, and under the previous symmetry assumptions, we find all the solutions to the semiclassical field equations in vacuum. The resulting counterpart to the Schwarzschild classical geometry substitutes the presence of an event horizon by a wormhole throat that connects an external asymptotically flat region with an internal asymptotic region possessing a naked singularity: there are no semiclassical vacuum solutions with well-defined Cauchy surfaces. We also show that the regularized Polyakov RSET allows for wormhole geometries of arbitrarily small throat radius. This analysis paves the way to future investigations of proper stellar configurations with an internal nonvacuum region.

The constraints imposed by the relativistic compressibility hypothesis on the square of the speed of sound in a medium are obtained. This result allows us to obtain purely hydrodynamic conditions for the physical reality of a perfect energy tensor representing the energetic evolution of a perfect fluid in local thermal equilibrium. The results are applied to the paradigmatic case of the generic ideal gases. Then the physical reality of the ideal gas Stephani models is analyzed and the Rainich-like theory for ideal gas solutions is built.

We investigate the propagation of gravitational waves in a cosmological background. Based on the framework of spatially covariant gravity, we derive the general quadratic action for gravitational waves. The spatial derivatives of the extrinsic curvature and the parity-violating terms are systematically introduced. Special attention is paid to the propagation speed of the gravitational waves. We find that it is possible to make the two polarization modes propagate in the same speed, which may differ from that of the light, in the presence of parity-violating terms in the action. In particular, we identify a large class of spatially covariant gravity theories with parity violation, in which both the polarization modes propagate in the speed of light. Our results indicate that there are more possibilities in the framework of spatially covariant gravity in light of the propagation speed of the gravitational waves.

Lorentz violation is motivated by quantum gravity and it is generically described by nondynamical tensors. In this work a Lorentz violating extension of general relativity is studied where a nondynamical tensor couples to the Weyl tensor. A family of static and spherically symmetric solutions in vacuum is found, confirming that there are consistent solutions with explicit Lorentz violation in dynamical spacetimes. These solutions produce an unconventional dependence of the gravitational redshift, which, in turn, leads to the first bounds on such a nondynamical tensor that do not rely on the physics of the early universe. Moreover, the bounds obtained in this work are competitive with respect to limits on similar nondynamical tensors.

In this paper, we construct compactifications of generic, higher-curvature Lovelock theories of gravity over direct product spaces of the type ${\mathcal{M}}_D={\mathcal{M}}_d\times {\mathcal{S}}^p$, with $D=d+p$ and $d\ge 5$, where ${\mathcal{S}}^p$ represents an internal, Euclidean manifold of positive constant curvature. We show that this can be accomplished by including suitable nonminimally coupled $p-1$-form fields with a field strength proportional to the volume form of the internal space. We provide explicit details of this constructions for the Einstein-Gauss-Bonnet theory in $d+2$ and $d+3$ dimensions by using 1- and 2-form fundamental fields and provide as well the formulas that allow one to construct the same family of compactification in any Lovelock theory from dimension $d+p$ to dimension $d$. These fluxed compactifications lead to an effective Lovelock theory on the compactified manifold, allowing one therefore to find, in the Einstein-Gauss-Bonnet case, black holes in the Boulware-Deser family.

The existence of light, fundamental bosonic fields is an attractive possibility that can be tested via black hole observations. We study the effect of a tidal field—caused by a companion star or black hole—on the evolution of superradiant scalar-field states around spinning black holes. For small tidal fields, the superradiant “cloud” puffs up by transitioning to excited states and acquires a new spatial distribution through transitions to higher multipoles, establishing new equilibrium configurations. For large tidal fields, the scalar condensates are disrupted; we determine numerically the critical tidal moments for this to happen and find good agreement with Newtonian estimates. We show that the impact of tides can be relevant for known black hole systems such as the one at the center of our Galaxy or the Cygnus X-1 system. The companion of Cygnus X-1, for example, will disrupt possible scalar structures around the black hole for gravitational couplings as large as $M\mu \sim 2\times {10}^{-3}$.

A variety of gauges are used in cosmological perturbation theory. These are often chosen in order to attribute physical properties to a particular choice of coordinates, or otherwise to simplify the form of the resultant equations. Calculations are then performed with the understanding that they could have been done in any gauge, and that transformations between different gauges can be made at will. We show that this logic can be extended to the domain of large density contrasts, where different types of perturbative expansion are required, but that the way in which gauges can be chosen in the presence of such structures is severely constrained. In particular, most gauges that are commonly considered in the cosmology literature are found to be unviable in the presence of nonlinear structures. This includes spatially flat gauge, synchronous gauge, comoving orthogonal gauge, total matter gauge, N-body gauge, and the uniform density gauge. In contrast, we find that the longitudinal gauge and the Newtonian motion gauge are both viable choices in both standard cosmological perturbation theory, and in the post-Newtonian perturbative expansions that are required in order to model non-linear structures.