The construction of accurate and consistent initial data for various binary parameters is a critical ingredient for numerical relativity simulations of the compact binary coalescence. In this article, we present an upgrade of the pseudospectral sgrid code, which enables us to access even larger regions of the binary neutron star parameter space. As a proof of principle, we present a selected set of first simulations based on initial configurations computed with the new code version. In particular, we simulate two millisecond pulsars close to their breakup spin, highly compact neutron stars with masses at about 98% of the maximum supported mass of the employed equation of state, and unequal-mass systems with mass ratios even outside the range predicted by population synthesis models ($q=2.03$). The discussed code extension will help us to simulate previously unexplored binary configurations. This is a necessary step to construct and test new gravitational-wave approximants and to interpret upcoming binary neutron star merger observations. When we construct initial data, we have to specify various parameters, such as a rotation parameter for each star. Some of these parameters do not have direct physical meaning, which makes comparisons with other methods or models difficult. To facilitate this, we introduce simple estimates for the initial spin, momentum, mass, and center of mass (c.m.) of each individual star.

When two relativistically boosted, nonspinning black holes pass by one another on a scattering trajectory, we might expect the tidal interaction to spin up each black hole. We present the first exploration of this effect, appearing at fourth post-Newtonian order, with full numerical relativity calculations. The basic setup for the calculations involves two free parameters: the initial boost of each black hole and the initial angle between the velocity vectors and a line connecting the centers of the black holes, with zero angle corresponding to a head-on trajectory. To minimize gauge effects, we measure final spins only if the black holes reach a final separation of at least $20M$. Fixing the initial boost, we find that as the initial angle decreases toward the scattering/nonscattering limit, the spin-up grows nonlinearly. In addition, as initial boosts are increased from $0.42c$ to $0.78c$, the largest observed final dimensionless spin on each black hole increases nonlinearly from 0.02 to 0.20. Based on these results, we conclude that much higher spin-ups may be possible with larger boosts, although achieving this will require improved numerical techniques.

We show that a simple subclass of Horndeski theory can describe a time crystal universe. The time crystal universe can be regarded as a baby universe nucleated from a flat space, which is mediated by an extension of Giddings-Strominger instanton in a 2-form theory dual to the Horndeski theory. Remarkably, when a cosmological constant is included, de Sitter universe can be created by tunneling from the time crystal universe. It gives rise to a past completion of an inflationary universe.

The implications of the recently proposed trans-Planckian censorship conjecture (TCC) are analyzed in the context of warm inflation. It is found that for a single-stage accelerated expansion the constraints imposed by the censorship are roughly the same as for cold inflation. Next, we study how a two-stage inflationary expansion with an intermediate radiation-dominated era can alleviate the bounds imposed by the censorship. For a demonstrative toy model we found $r<{10}^{-23}$, but can be $r<{10}^{-5}$ for a weaker form of TCC for the later stages of expansion, while still satisfying the other swampland conditions.

By making use of a class of a steep exponential type of potentials, which has been recently used to describe quintessential inflation, we show how a unified picture for inflation, dark energy, and dark matter can emerge entirely through dissipative effects. Dissipation provides a way to extend the applicability of a larger class of these potentials in the sense of leading to a consistent early Universe inflationary picture and producing observables in agreement with the Planck legacy data. Likewise, dissipative effects lead to dark matter production with consistent abundances and, toward the recent time of the Universe, drives the potential energy of the scalar quintessential field to dominate again, essentially mimicking a cosmological constant by today, with all cosmological parameters consistent with the observations. Both early and late Universes are connected and have no kination period in between.

We show that whenever the symmetry group of a field theory commutes with one or more antiunitary operators $T$, which do not have to but may represent the reversal of physical time, the number of linearly independent contact two-body (quartic) terms is determined by the number of tensors that are even, or by the number of tensors that are odd, under such $T$. The choice depends on the sign of $T^2$ and on the statistics of the fields. The theorem enables one to circumvent the usual computation of the Fierz matrix in determining the independent interaction terms. Some physical examples of current interest in many-body physics are discussed.

Nonentral heavy-ion collisions generate the strongest magnetic field of the order of $10^{18}–{10}^{19}$ Gauss due to the electric current produced by the positively charged spectators that travel at nearly the speed of light. Such transient electromagnetic fields may induce various novel effects in the hydrodynamic description of the quark gluon plasma for noncentral heavy-ion collisions. We investigate the longitudinal acceleration effects on the $1+1$ dimensional relativistic magnetohydrodynamics (MHD) with homogenous transverse magnetic fields. Exact solution of such MHD with a special equation of state (EoS) is presented, and we analyze the proper time evolution of the system energy density for general EoS. We find that the longitudinal acceleration parameter ${\lambda }^{*}$, magnetic field decay parameter $a$, equation of state $\kappa$, and initial magnetization ${\sigma }_0$ have nontrivial effects on the evolutions of the system energy density and temperature profile.

It has recently been shown explicitly that the high-energy scattering amplitude of the longitudinal modes of massive spin-2 Kaluza-Klein states in compactified five-dimensional gravity, which would naively grow like $\mathcal{O}(s^5)$, grow only like $\mathcal{O}(s)$. Since the individual contributions to these amplitudes do grow like $\mathcal{O}(s^5)$, the required cancellations between these individual contributions result from intricate relationships between the masses of these states and their couplings. Here we report the explicit form of these sum-rule relationships which ensure the necessary cancellations for elastic scattering of spin-2 Kaluza-Klein states in a Randall-Sundrum model. We consider an anti–de Sitter space of arbitrary curvature, including the special case of a toroidal compactification in which the curvature vanishes. The sum rules demonstrate that the cancellations at $\mathcal{O}(s^5)$ and $\mathcal{O}(s^4)$ are generic for a compact extra dimension and arise from the Sturm-Liouville structure of the eigenmode system in the internal space. Separately, the sum rules at $\mathcal{O}(s^3)$ and $\mathcal{O}(s^2)$ illustrate the essential role of the radion mode of the extradimensional metric, which is the dynamical mode related to the size of the internal space.

We study the collider, astrophysical, and cosmological constraints on the dark matter sector of a conformal model within the framework of the freeze-out as well as the freeze-in mechanism. The model has a dark sector with strong self-interactions. This sector couples weakly with the Standard Model particles via a scalar messenger. The lightest dark sector particle is a pionlike fermion antifermion bound state. We find that the model successfully satisfies the constraints coming from the Higgs decay to the visible as well as the invisible sector. We have used the results of the dark matter direct detection experiments, such as XENON1T, in order to impose bounds on the parameters of the model. The model satisfies the indirect detection constraints of gamma ray from the galactic center and Dwarf spheroidal galaxies. We also determine the parameter range for which it satisfies the astrophysical constraints on the dark matter self-coupling.

In a recent paper we presented a systematic way of testing the seesaw origin of neutrino mass in the context of the minimal left-right symmetric model. The essence of the program is to exploit lepton number violating decays of doubly charged scalars, particles which lie at the heart of the Higgs-mechanism-based seesaw, to probe the Dirac neutrino mass term which in turn enters directly into a number of physical processes including the decays of right-handed neutrinos into the $W$ boson and left-handed charged leptons. In this longer version we discuss at length these and related processes, and we offer some missing technical details. We also carefully analyze the physically appealing possibility of a parity conserving Yukawa sector showing that the neutrino Dirac mass matrix can be analytically expressed as a function of light and heavy neutrino masses and mixing, without resorting to any additional discrete symmetries, a context in which the seesaw mechanism can be disentangled completely. When parity does get broken, we show that, in the general case, only the Hermitian part of the Dirac mass term is independent which substantially simplifies the task of testing experimentally the origin of neutrino mass. We illustrate this program through some physical examples that allow simple analytical expressions. Our work shows that the minimal left-right symmetric model is a self-contained theory of neutrino mass which can be in principle tested at the LHC or the next hadron collider.

We present a calculation of the pion valence quark distribution extracted using the formalism of reduced Ioffe-time pseudodistributions or more commonly known as pseudo-PDFs. Our calculation is carried out on two different $2+1$ flavor QCD ensembles using the isotropic-clover fermion action, with lattice dimensions $24^3\times 64$ and $32^3\times 96$ at the lattice spacing of $a=0.127\mathrm{fm}$, and with the quark mass equivalent to a pion mass of $m_{\pi }\simeq 415\mathrm{MeV}$. We incorporate several combinations of smeared-point and smeared-smeared pion source-sink interpolation fields in obtaining the lattice QCD matrix elements using the summation method. After one-loop perturbative matching and combining the pseudodistributions from these two ensembles, we extract the pion valence quark distribution using a phenomenological functional form motivated by the global fits of parton distribution functions. We also calculate the lowest four moments of the pion quark distribution through the “operator product expansion without operator product expansion.” We present a qualitative comparison between our lattice QCD extraction of the pion valence quark distribution with that obtained from global fits and previous lattice QCD calculations.

We present two determinations of the strong coupling ${\alpha }_s$. The first one is from the static energy at three-loop accuracy, and may be considered an update of earlier determinations by some of us. The new analysis includes new lattice data at smaller lattice spacings, and reaches distances as short as 0.0237 fm. We present a comprehensive and detailed estimate of the error sources that contribute to the uncertainty of the final result, ${\alpha }_s(M_Z)=0.11660_{-0.00056}^{+0.00110}$. The second determination is based on lattice data for the singlet free energy at finite temperature up to distances as small as 0.0081 fm, from which we obtain ${\alpha }_s(M_Z)=0.11638_{-0.00087}^{+0.00095}$.

We implement a Monte Carlo sampling strategy to extract helicity parton densities and their uncertainties from a reference set of longitudinally polarized scattering data, chosen to be that used in the DSSV14 global analysis. Instead of adopting the simplest possible functional forms for the helicity parton distributions and imposing certain restrictions on their parameter space in order to constrain them, we employ redundant, flexible parametrizations and fit them to a large number of Monte Carlo replicas of the existing data. The optimum fit and its uncertainty estimates are then assumed to be given by the statistical average of the obtained ensemble of replicas of helicity parton densities and their corresponding variance, respectively. We compare our results to those obtained by the traditional fitting approach and to the uncertainty estimates derived with the robust Lagrange multiplier method, finding good agreement. As a first application of our new set of replicas, we discuss the impact of the recent STAR dijet data in further constraining the elusive gluon helicity density through the reweighting method.

We deform a defect conformal field theory by an exactly marginal bulk operator and we consider the dependence on the marginal coupling of flat and spherical defect expectation values. For odd-dimensional defects, we find a different qualitative behavior for the flat and spherical case, generalizing to arbitrary dimensions the line-circle anomaly of superconformal Wilson loops. In the even-dimensional case, on the other hand, we find a logarithmic divergence which can be related to a $a$-type anomaly coefficient. This coefficient, for defect theories, is not invariant on the conformal manifold and its dependence on the bulk coupling is controlled to all orders by the one-point function of the associated exactly marginal operator. In particular, our results imply a nontrivial dependence on the bulk coupling for the recently proposed defect $C$-function. We finally apply our general result to a few specific examples, including superconformal Wilson loops and Rényi entropy.

We study the return amplitude, which is the overlap between the initial state and the time-evolved state, in the Sachdev-Ye-Kitaev (SYK) model. Initial states are taken to be product states in a spin basis. We numerically study the return amplitude by exactly diagonalizing the Hamiltonian. We also derive the analytic expression for the return amplitude in random matrix theory. The SYK results agree with the random matrix expectation. We also study the time evolution under the different Hamiltonian that is originally proposed to describe the traversable wormholes in projected black holes in the context of holography. The time evolution now depends on the choice of initial product states. The results are again explained by random matrix theory. In the symplectic ensemble cases, we observe an interesting pattern of the return amplitude in which they show the second dip, ramp, and plateaulike behavior.

It has been observed that the area product of horizons for many black hole solutions is mass independent and satisfies the universality relation $A_{+}{A}_{-}=(8\pi {)}^{2}N$, where $N$ is related to the quantized charges of the solution as angular momentum and electric charge. In this work we study the area product for black hole and black ring solutions with conical singularity. We find that the area product is still mass independent and regardless of the horizon topology, the conical characteristic ($\kappa$) of the solutions, appears in the universality relation as $\kappa A_{+}{A}_{-}=(8\pi {)}^{2}N$. We also check that the first law of black hole inner mechanics is satisfied for these solutions.

We apply the instanton counting method to study a class of four-dimensional $\mathcal{N}=2$ supersymmetric quiver gauge theories with alternating SO and USp gauge groups. We compute the partition function in the $\mathrm{\Omega }$-background and express it as functional integrals over density functions. Applying the saddle point method, we derive the limit shape equations which determine the dominant instanton configurations in the flat space limit. The solution to the limit shape equations gives the Seiberg-Witten geometry of the low energy effective theory. As an illustrating example, we work out explicitly the Seiberg-Witten geometry for linear quiver gauge theories. Our result matches the Seiberg-Witten solution obtained previously using the method of brane constructions in string theory.

The problem of eliminating divergences arising in quantum gravity is generally addressed by modifying the classical Einstein-Hilbert action. These modifications might involve the introduction of a local supersymmetry, the addition of terms that are higher order in the curvature to the action, or invoking compactification of superstring theory from ten to four dimensions. An alternative to these approaches is to introduce a Lagrange multiplier field that restricts the path integral to field configurations that satisfy the classical equations of motion; this has the effect of doubling the usual one-loop contributions and of eliminating all effects beyond one loop. We show how this reduction of loop contributions occurs and find the gauge invariances present when such a Lagrange multiplier is introduced into the Yang-Mills and Einstein-Hilbert actions. Moreover, we quantize using the path integral, discuss the renormalization, and then show how Becchi-Rouet-Stora-Tyutin (BRST) invariance can be used to both demonstrate that unitarity is retained and to find BRST relations between Green’s functions. In the Appendices we show how background field quantization can be implemented, consider the use of a Lagrange multiplier field to restrict higher-order contributions in supersymmetric theories, and derive the BRST equations satisfied by the generating functional.