It is well known that entanglement is widespread in quantum field theory, in the following sense: every Reeh-Schlieder state contains entanglement between any two spatially separated regions. This applies, in particular, to the vacuum of a noninteracting scalar theory in Minkowski spacetime. Discussions on entanglement in field theory have focused mainly on subsystems containing infinitely many degrees of freedom—typically, the field modes that are supported within a compact region of space. In this article, we study entanglement in subsystems made of finitely many field degrees of freedom, in a free scalar theory in $D+1$-dimensional Minkowski spacetime. The focus on finitely many modes of the field is motivated by the finite capabilities of real experiments. We find that entanglement between finite-dimensional subsystems is not common at all, and that one needs to carefully select the support of modes for entanglement to show up. We also find that entanglement is increasingly sparser in higher dimensions. We conclude that entanglement in Minkowski spacetime is significantly less ubiquitous than normally thought.

The event horizon of a dynamical black hole is generically a nonsmooth hypersurface. We classify the types of nonsmooth structure that can arise on a horizon that is smooth at late time. The classification includes creases, corners and caustic points. We prove that creases and corners form spacelike submanifolds of dimension 2,1 and that caustic points form a set of dimension at most 1. We classify “perestroikas” of these structures, in which they undergo a qualitative change at an instant of time. A crease perestroika gives an exact local description of the event horizon near the “instant of merger” of a generic black hole merger. Other crease perestroikas describe horizon nucleation or collapse of a hole in a toroidal horizon. Caustic perestroikas, in which a pair of caustic points either nucleate or annihilate, provide a mechanism for creases to decay. We argue that properties of quantum entanglement entropy suggest that creases might contribute to black hole entropy. We explain that a “Gauss-Bonnet” term in the entropy is nontopological on a nonsmooth horizon, which invalidates previous arguments against such a term.

We present a numerical framework for modeling extended hyperelastic bodies based on a Lagrangian formulation of general relativistic elasticity theory. We use finite element methods to discretize the body, then use the semidiscrete action to derive ordinary differential equations of motion for the discrete nodes. The nodes are evolved in time using fourth-order Runge-Kutta. We validate our code against the normal modes of oscillation of a hyperelastic sphere, which are known analytically in the limit of small (linear), slow (Newtonian) oscillations. The algorithm displays second order convergence. This numerical framework can be used to obtain the orbital motion and internal dynamics of a hyperelastic body of any shape, for any spacetime metric, and for varying hyperelastic energy models.

We present an analytic method for calculating the tidal response function of a nonrotating and a slowly rotating black hole from the Teukolsky equation in the small-frequency and near-horizon limit. We point out that in the relativistic context, there can be two possible definitions of the tidal Love numbers and the dissipative part that arises from the tidal response function. Our results suggest that both of these definitions predict zero tidal Love numbers for a nonrotating black hole. On the other hand, for a slowly rotating black hole in a generic tidal environment, these two definitions of the tidal Love numbers do not coincide. While one procedure suggests zero tidal Love numbers, the other procedure gives purely imaginary tidal Love numbers. As expected, the dissipative terms differ as well. We emphasize that in our analysis, we keep all the terms linear in the frequency, unlike previous works in the literature. Following this, we propose a procedure to calculate the tidal response function—and hence the Love numbers—for an arbitrarily rotating black hole.

We derive new terms in the post-Newtonian (PN) expansion of the generalized redshift invariant $⟨u^t{⟩}_{\tau }$ for a small body in eccentric, equatorial orbit about a massive Kerr black hole. The series is computed analytically using the Teukolsky formalism for first-order black hole perturbation theory, along with the Chrzanowski, Cohen, Kegeles method for metric reconstruction using the Hertz potential in ingoing radiation gauge. Modal contributions with small values of $l$ are derived via the semianalytic solution of Mano-Suzuki-Takasugi, while the remaining values of $l$ to infinity are determined via direct expansion of the Teukolsky equation. Each PN order is calculated as a series in eccentricity $e$ but kept exact in the primary black hole’s spin parameter $a$. In total, the PN terms are expanded to $e^{16}$ through 6PN relative order, and separately to $e^{10}$ through 8PN relative order. Upon grouping eccentricity coefficients by spin dependence, we find that many resulting component terms can be simplified to closed-form functions of eccentricity, in close analogy to corresponding terms derived previously in the Schwarzschild limit. We use numerical calculations to compare convergence of the full series to its Schwarzschild counterpart and discuss implications for gravitational wave analysis.

We compute the scalar tidal Love numbers and static response coefficients associated with several rotating black holes in higher dimensions, including Myers-Perry black holes, black rings, and black strings. These coefficients exhibit a rich and complex structure as a function of the black hole parameters and multipoles. Our results agree in limiting cases with known and new expressions for various lower-dimensional black holes. In particular, we provide an alternative approach to the computation of the static response of Kerr black holes as a limiting case of the boosted black string.

Charged Dirac fields minimally coupled to gravity have spherically symmetric wormhole solutions known as Einstein-Dirac-Maxwell (EDM) wormholes. EDM wormholes do not make use of exotic matter and exist in asymptotically flat general relativity. We construct static spherically symmetric EDM wormhole configurations in quantum field theory using semiclassical approximations for gravity and the electromagnetic field. Our framework is able to describe a broader class of EDM wormholes than previously considered and, being constructed in quantum field theory, puts EDM wormholes on firmer theoretical ground.

The idea of neutrino-assisted early dark energy ($\nu \mathrm{EDE}$), where a coupling between neutrinos and the scalar field that models early dark energy (EDE) is considered, was introduced with the aim of reducing some of the fine-tuning and coincidence problems that appear in usual EDE models. In order to be relevant in ameliorating the $H_0$ tension, the contribution of EDE to the total energy density ($f_{\mathrm{EDE}}$) should be around 10% near the redshift of matter-radiation equality. We verify under which conditions $\nu \mathrm{EDE}$ models can fulfill these requirements for a model with a quartic self-coupling of the EDE field and an exponential coupling to neutrinos. We find that in the situation where the EDE field is frozen initially, the contribution to $f_{\mathrm{EDE}}$ can be significant but it is not sensitive to the neutrino-EDE coupling and does not address the EDE coincidence problem. On the other hand, if the EDE field starts already dynamical at the minimum of the effective potential, it tracks this time-dependent minimum that presents a feature triggered by the neutrino transition from relativistic to nonrelativistic particles. This feature generates $f_{\mathrm{EDE}}$ in a natural way at around this transition epoch, which roughly coincides with the matter-radiation equality redshift. For the set of parameters that we considered we did not find values that satisfy the requirements on the background cosmological evolution to mitigate the Hubble tension in a natural way in this particular $\nu \mathrm{EDE}$ model.

The symmetron field has an environment (density) dependent behavior which is a common feature of the models with the screening mechanism and results in a rich phenomenology. This model can produce domain walls between regions with different densities. We consider this aspect and study the physics of domain walls in between (underdensity) voids and (overdensity) halo structures. The (spherical) domain walls exert a repulsive force on a test mass outside of the wall while a test mass inside of the wall sees no force because of it. This makes the structures outside the voids go further to a larger radius. Effectively, this means the voids are becoming larger in this scenario in comparison to the standard model of cosmology. Interestingly, this makes voids emptier which may shed light on Peebles’ void phenomenon.

Model-independent mass limits assess the robustness of current cosmological measurements of the neutrino mass scale. Consistency between high-multipole and low-multiple cosmic microwave background observations measuring such scale further valuates the constraining power of present data. We derive here up-to-date limits on neutrino masses and abundances exploiting either the Data Release 4 of the Atacama Cosmology Telescope (ACT) or the South Pole Telescope polarization measurements from SPT-3G, envisaging different nonminimal background cosmologies and marginalizing over them. By combining these high-$\ell$ observations with supernova Ia, baryon acoustic oscillations (BAO), redshift space distortions (RSD) and a prior on the reionization optical depth from WMAP data, we find that the marginalized bounds are competitive with those from Planck analyses. We obtain $\sum m_{\nu }<0.139\mathrm{eV}$ and $N_{\mathrm{eff}}=2.82\pm 0.25$ in a dark energy quintessence scenario, both at 95% CL. These limits translate into $\sum m_{\nu }<0.20\mathrm{eV}$ and $N_{\mathrm{eff}}=2.79_{-0.28}^{+0.30}$ after marginalizing over a plethora of well-motivated fiducial models. Our findings reassess both the strength and the reliability of cosmological neutrino mass constraints.

Earth neutrino tomography is a realistic possibility with current and future neutrino detectors, complementary to geophysics methods. The two main approaches are based on either partial absorption of the neutrino flux as it propagates through Earth (at energies about a few TeV) or on coherent Earth matter effects affecting the neutrino oscillations pattern (at energies below a few tens of GeV). In this work, we consider the latter approach, focusing on supernova neutrinos with tens of MeV. Whereas at GeV energies, Earth matter effects are driven by the atmospheric mass-squared difference, at energies below $\sim 100\mathrm{MeV}$, it is the solar mass-squared difference that controls them. Unlike solar neutrinos, which suffer from significant weakening of the contribution to the oscillatory effect from remote structures due to the neutrino energy reconstruction capabilities of detectors, supernova neutrinos can have higher energies and, thus, can better probe Earth’s interior. We shall revisit this possibility, using the most recent neutrino oscillation parameters and up-to-date supernova neutrino spectra. The capabilities of future neutrino detectors, such as DUNE, Hyper-Kamiokande, and JUNO, are presented, including the impact of the energy resolution and other factors. Assuming a supernova burst at 10 kpc, we show that the average Earth’s core density could be determined within $\lesssim 10\%$ at $1\sigma$ confidence level, Hyper-Kamiokande being, with its largest mass, the most promising detector to achieve this goal.

Motivated by recent experimental initiatives, such as at the Helmholtz International Beam line for Extreme Fields at the European X-ray Free Electron Laser, we calculate the birefringent scattering of x rays at the combined field of two optical (or near-optical) lasers and compare various scenarios. In order to facilitate an experimental detection of quantum vacuum diffraction and birefringence, special emphasis is placed on scenarios where the difference between the initial and final x-ray photons is maximized. Apart from their polarization, these signal and background photons may differ in propagation direction (corresponding to scattering angles in the millirad regime) and possibly energy.

In this paper, we explore the recursive structure of Baikov representations for Feynman integrals. We demonstrate that the various Baikov representations for all sectors of an integral family can be organized in a treelike structure. Using this structure, we show that the symbol letters of one-loop Feynman integrals can be written in terms of minors of a matrix associated with the top sector. Nontrivial relations among these symbol letters can then be easily discovered using results from linear algebra.

Motivated by the recent rare $B$ decays measurements, we study the matching procedure of operators $O_9$, $O_{10}$ in the low energy effective Hamiltonian and operators in the Standard Model effective theory (SMEFT). It is noticed that there are more related operators in the SMEFT whose coefficients cannot be determined only from the low-energy data from $B$ physics. We demonstrate how to determine these coefficients with some new physics models, like the $Z^{\prime }$ model and leptoquark models, and then consider how to probe these operators of SMEFT at high energy by using the process ${\mu }^{+}{\mu }^{-}\to tc$ at future muon colliders, which can provide complementary information except for ${\mu }^{+}{\mu }^{-}\to bs$ on the underlying models which lead to rare $B$ decay processes. We perform a Monte Carlo study (a hadron level analysis) to show how to separate the signal events from the SM background events and estimate the sensitivity to the Wilson coefficients for different models.

We present a set of Lorentz invariant kinematic variables for reconstructing mass of semi-invisible decaying particles pair-produced at lepton colliders, $m_{\mathrm{RC}}^{\min }$, $m_{\mathrm{RC}}^{\max }$, and $m_{\mathrm{LSP}}^{\max }$, with analytical formulas. They give the minimal and maximum bounds of the decaying particle mass and upper bound of the invisible particle mass. In the search of new physics, these variables can greatly enhance the statistical significance of signal. For the process of smuon pair production at $\sqrt{s}=240\mathrm{GeV}$ lepton collider of $5{\mathrm{ab}}^{-1}$, the cross section detection limit is pushed by one order, and the expected exclusion and discovery limits are set above $\sqrt{s}/2$ and go into the off-shell region. Moreover, these variables can also be used to improve the precision of $W$-boson mass measurement in full leptonic decayed channel. At a future lepton collider, the precision can reach to 2–3 MeV level.

We analyze the potential of future high-energy deep-inelastic scattering (DIS) experiments to probe new physics within the framework of the Standard Model effective field theory (SMEFT). We perform a detailed study of SMEFT probes at a future Large Hadron-electron Collider (LHeC) and a Future Circular lepton-hadron Collider (FCC-eh) machine, and extend previous simulations of the potential of an electron-ion collider (EIC) to include $Z$-boson vertex corrections. Precision $Z$-pole constraints on vertex corrections suffer from numerous degeneracies in the Wilson-coefficient parameter space. We find that both the LHeC and the FCC-eh can help remove these degeneracies present in the existing global fits of precision $Z$-pole observables and LHC data. The FCC-eh and LHeC will in many cases improve upon the existing precision electroweak bounds on the SMEFT parameter space. This highlights the important role of precision DIS measurements for new physics studies.

We present a lattice QCD study of the contribution of the isovector quark chromoelectric dipole moment (qcEDM) operator to the nucleon electric dipole moments (nEDM). The calculation was carried out on four $2+1+1$ flavor highly improved staggered quark (HISQ) ensembles generated by the MILC Collaboration. Wilson-clover quarks were used to construct correlation functions. This clover-on-HISQ formulation is not fully $O(a)$ improved, and gives rise to additional systematics over and above those due to removing excited state contributions to getting ground-state matrix elements, and the final chiral and continuum extrapolations to get the physical result. We use the nonsinglet axial Ward identity (AWI) including corrections up to $O(a)$ to show how to control the power-divergent mixing of the isovector qcEDM operator with the lower-dimensional pseudoscalar operator. The residual corrections are observed to give rise to $O(25\%)$ violations in relations arising from the AWI. We devise three methods attempting to control the resulting uncertainty in the $CP$-violating form factor; each of these, however, can have large $O(a^2)$ corrections. Preliminary results for the nEDM due to qcEDM are presented choosing the method giving the most uniform behavior.

We compute the structure-dependent axial and vector form factors for the radiative leptonic decays $D_s\to \ell {\nu }_{\ell }\gamma$, where $\ell$ is a charged lepton, as functions of the energy of the photon in the rest frame of the $D_s$ meson. We work in the electroquenched approximation, using gauge-field configurations with $2+1+1$ sea-quark flavors generated by the European Twisted Mass Collaboration and the results have been extrapolated to the continuum limit. For the vector form factor we observe a very significant partial cancellation between the contributions from the emission of the photon from the strange quark and that from the charm quark. The results for the form factors are used to test the reliability of various Anzätze based on single-pole dominance and its extensions, and we present a simple parametrization of the form factors which fits our data very well and which can be used in future phenomenological analyses. Using the form factors we compute the differential decay rate and the branching ratio for the process $D_s\to e{\nu }_e\gamma$ as a function of the lower cutoff on the photon energy. With a cutoff of 10 MeV for example, we find a branching ratio of $\mathrm{Br}(E_{\gamma }>10\mathrm{MeV})=4.4(3)\times {10}^{-6}$ which, unlike some model calculations, is consistent with the upper bound from the BESIII experiment $\mathrm{Br}(E_{\gamma }>10\mathrm{MeV})<1.3\times {10}^{-4}$ at 90% confidence level. Even for photon energies as low as 10 MeV, the decay $D_s\to e{\nu }_e\gamma$ is dominated by the structure-dependent contribution to the amplitude (unlike the decays with $\ell =\mu$ or $\tau$), confirming its value in searches for hypothetical new physics as well as in determining the Cabibbo-Kobayashi-Maskawa parameters at $O({\alpha }_{\mathrm{em}})$, where ${\alpha }_{\mathrm{em}}$ is the fine-structure constant.

In present work, a relation that connects the integrated correlation function of a trapped two-particle system to infinite volume particles scattering phase shift is derived. It has the potential to provide an alternative approach for extracting two-particle scattering phase shift from integrated correlation function in lattice simulation at small Euclidean time region. Both (i) perturbation calculation of ($1+1$)-dimensional lattice Euclidean field theory model of fermions interacting with a contact interaction and (ii) Monte Carlo simulation of a 1D exactly solvable quantum mechanics model are carried out to test the proposed relation. In contrast to conventional two-step approach of extracting energy levels from temporal correlation function in lattice simulation at large Euclidean time first and then applying Lüscher formula to convert energy levels into scattering phase shifts, we show that the difference of integrated correlation functions between interacting and noninteracting trapped systems converges rapidly to infinite volume limit that is given in terms of scattering phase shifts at small Euclidean time region.

The quantum simulation of fermionic gauge field theories is one of the anticipated uses of quantum computers in the noisy intermediate-scale quantum (NISQ) era. Recently work has been done to simulate properties of the fermionic ${\mathbb{Z}}_2$ gauge field theory in $(1+1)\mathrm{D}$ and the pure gauge theory in $(2+1)\mathrm{D}$. In this work, we investigate various options for simulating the fermionic ${\mathbb{Z}}_2$ gauge field theory in $(2+1)\mathrm{D}$. To simulate the theory on a NISQ device it is vital to minimize both the number of qubits used and the circuit depth. In this work we propose ways to optimize both criteria for simulating time dynamics. In particular, we develop a new way to simulate this theory on a quantum computer, with minimal qubit requirements. We provide a quantum circuit for simulating a single first-order Trotter step that minimizes the number of 2-qubit gates needed and gives comparable results to methods requiring more qubits. Furthermore, we investigate variational Trotterization approaches that allow us to further decrease the circuit depth.