We review and extend the model derived in Garcia-Recio et al. [Phys. Rev. D 83, 016007 (2011)] to address the dynamics of the low-lying even-parity meson resonances. This model is based on a coupled-channels spin-flavor extension of the chiral Weinberg-Tomozawa Lagrangian. This interaction is then used to study the $S$-wave meson-meson scattering involving members not only of the $\pi$ octet, but also of the $\rho$ nonet. In this work, we study in detail the structure of the SU(6)-symmetry-breaking contact terms that respect (or softly break) chiral symmetry. We derive the most general local (without involving derivatives) terms consistent with the chiral-symmetry-breaking pattern of QCD. After introducing sensible simplifications to reduce the large number of possible operators, we carry out a phenomenological discussion of the effects of these terms. We show how the inclusion of these pieces leads to an improvement of the description of the $J^P=2^{+}$ sector, without spoiling the main features of the predictions obtained in the original model in the $J^P=0^{+}$ and $J^P=1^{+}$ sectors. In particular, we find a significantly better description of the $I^G(J^{PC})=0^{+}(2^{++})$, $1^{-}(2^{++})$ and the $I(J^P)=\frac{1}{2}(2^{+})$ sectors, which correspond to the $f_2(1270)$, $a_2(1320)$, and $K_2^{*}(1430)$ quantum numbers, respectively.

Models with quark and lepton compositeness predict the existence of colored partners of the Standard Model leptons. In this paper we study the LHC phenomenology of a charged colored lepton partner, namely the color octet electron, $e_8$, in an effective theory framework. We explore various mechanisms for resonant production of $e_8$’s. With the pair production channel, the 14 TeV LHC can probe $e_8$’s with masses up to 2.5 TeV (2.8 TeV) with $100{\mathrm{fb}}^{-1}$ ($300{\mathrm{fb}}^{-1}$) of integrated luminosity. A common feature in all the resonant production channels is the presence of two high-$p_T$ electrons and at least one high-$p_T$ jet in the final state. Using this feature, we implement a search method where the signal is a combination of pair and single production events. This method has potential to increase the LHC’s reach significantly. Using the combined signal, we estimate the LHC discovery potential for the $e_8$’s. Our analysis shows that the LHC with 14 TeV center-of-mass energy and $100{\mathrm{fb}}^{-1}$ ($300{\mathrm{fb}}^{-1}$) of integrated luminosity can probe $e_8$’s with masses up to 3.4 TeV (4 TeV) for the compositeness scale of 5 TeV.

We study the temperature dependence of the renormalized Polyakov loop in $2+1$ flavor QCD for temperatures $T<210\mathrm{MeV}$. We extend previous calculations by the HotQCD Collaboration using the highly improved staggered quark action and perform a continuum extrapolation of the renormalized Polyakov loop. We compare the lattice results with the prediction of noninteracting static-light hadron resonance gas, which describes the temperature dependence of the renormalized Polyakov loop up to $T<140\mathrm{MeV}$ but fails above that temperature. Furthermore, we discuss the temperature dependence of the light and strange quark condensates.

We present the results of calculations of the $p^4$ and $p^6$ order low-energy constants for the chiral Lagrangian with tensor sources for both two and three flavors of pseudoscalar mesons. This is a generalization of our previous work on similar calculations without tensor sources in terms of the quark self-energy $\Sigma (p^2)$, based on the first principle derivation of the low-energy effective Lagrangian and computation of the low-energy constants with some rough approximations. With the help of partial integration and some epsilon relations, we find that some $p^6$ order operators with tensor sources appearing in the literature are related to each other. That leaves 98 independent terms for $n$-flavor, 92 terms for three-flavor, and 65 terms for two-flavor cases. We also find that the odd-intrinsic-parity chiral Lagrangian with tensor sources cannot independently exist in any order of low-energy expansion.

We use holography to study ($3+1$)-dimensional $\mathcal{N}=4$ supersymmetric $\mathrm{SU}(N_c)$ Yang-Mills theory (SYM) in the large-$N_c$ and large-coupling limits, with a ($2+1$)-dimensional interface where the Yang-Mills coupling or $\theta$ angle changes value, or “jumps.” We consider interfaces that either break all supersymmetry or that preserve half of the $\mathcal{N}=4$ supersymmetry thanks to certain operators localized to the interface. Specifically, we compute the expectation values of a straight timelike Wilson line and of a rectangular Wilson loop in the fundamental representation of $\mathrm{SU}(N_c)$. The former gives us the self-energy of a heavy test charge while the latter gives us the potential between heavy test charges. A jumping coupling or $\theta$ angle acts much like a dielectric interface in electromagnetism: the self-energy or potential includes the effects of image charges. $\mathcal{N}=4$ SYM with a jumping $\theta$ angle may also be interpreted as the low-energy effective description of a fractional topological insulator, as we explain in detail. For nonsupersymmetric interfaces, we find that the self-energy and potential are qualitatively similar to those in electromagnetism, despite the differences between $\mathcal{N}=4$ SYM and electromagnetism. For supersymmetric interfaces, we find dramatic differences from electromagnetism which depend sensitively on the coupling of the test charge to the adjoint scalars of $\mathcal{N}=4$ SYM. In particular, we find one special case where a test charge has a vanishing image charge.

We develop the theory of conformal blocks in ${\mathrm{CFT}}_d$ expressing them as power series with Gegenbauer polynomial coefficients. Such series have a clear physical meaning when the conformal block is analyzed in radial quantization: individual terms describe contributions of descendants of a given spin. Convergence of these series can be optimized by a judicious choice of the radial quantization origin. We argue that the best choice is to insert the operators symmetrically. We analyze in detail the resulting “$\rho$-series” and show that it converges much more rapidly than for the commonly used variable $z$. We discuss how these conformal block representations can be used in the conformal bootstrap. In particular, we use them to derive analytically some bootstrap bounds whose existence was previously found numerically.

Perturbations of the linearized vacuum Einstein equations in the Bondi-Sachs formulation of general relativity can be derived from a single master function with spin weight two, which is related to the Weyl scalar ${\Psi }_0$, and which is determined by a simple wave equation. By utilizing a standard spin representation of tensors on a sphere and two different approaches to solve the master equation, we are able to determine two simple and explicitly time-dependent solutions. Both solutions, of which one is asymptotically flat, comply with the regularity conditions at the vertex of the null cone. For the asymptotically flat solution we calculate the corresponding linearized perturbations, describing all multipoles of spin-2 waves that propagate on a Minkowskian background spacetime. We also analyze the asymptotic behavior of this solution at null infinity using a Penrose compactification and calculate the Weyl scalar ${\Psi }_4$. Because of its simplicity, the asymptotically flat solution presented here is ideally suited for test bed calculations in the Bondi-Sachs formulation of numerical relativity. It may be considered as a sibling of the Bergmann-Sachs or Teukolsky-Rinne solutions, on spacelike hypersurfaces, for a metric adapted to null hypersurfaces.

We develop an approach for linking the power spectra, bispectrum, and trispectrum to the geometric and kinematical features of multifield inflationary Lagrangians. Our geometric approach can also be useful in determining when a complicated multifield model can be well approximated by a model with one, two, or a handful of fields. To arrive at these results, we focus on the mode interactions in the kinematical basis, starting with the case of no sourcing and showing that there is a series of mode conservation laws analogous to the conservation law for the adiabatic mode in single-field inflation. We then treat the special case of a quadratic potential with canonical kinetic terms, showing that it produces a series of mode sourcing relations identical in form to that for the adiabatic mode. We build on this result to show that the mode sourcing relations for general multifield inflation are an extension of this special case but contain higher-order covariant derivatives of the potential and corrections from the field metric. In parallel, we show how the mode interactions depend on the geometry of the inflationary Lagrangian and on the kinematics of the associated field trajectory. Finally, we consider how the mode interactions and effective number of fields active during inflation are reflected in the spectra and introduce a multifield consistency relation, as well as a multifield observable ${\beta }_2$ that can potentially distinguish two-field scenarios from scenarios involving three or more effective fields.

When inflation is driven by a pseudoscalar field $\chi$ coupled to vectors as $\frac{\alpha }{4}\chi F\tilde{F}$, this coupling may lead to a copious production of gauge quanta, which in turns induces non-Gaussian and non-scale-invariant corrections to curvature perturbations. We point out that this mechanism is generically at work in a broad class of inflationary models in supergravity, hence providing them with a rich set of observational predictions. When the gauge fields are massless, significant effects on cosmic microwave background scales emerge only for relatively large $\alpha$. We show that in this regime, the curvature perturbations produced at the last stages of inflation have a relatively large amplitude that is of the order of the upper bound set by the possible production of primordial black holes by non-Gaussian perturbations. On the other hand, within the supergravity framework described in our paper, the gauge fields can often acquire a mass through a coupling to additional light scalar fields. Perturbations of these fields modulate the duration of inflation, which serves as a source for non-Gaussian perturbations of the metric. In this regime, the bounds from primordial black holes are parametrically satisfied and non-Gaussianity of the local type can be generated at the observationally interesting level $f_{\mathrm{NL}}\sim \mathcal{O}(10)$.

There are strong indications that the process of conversion of a neutron star into a strange quark star proceeds as a strong deflagration implying that in a few milliseconds almost the whole star is converted. Starting from the three-dimensional hydrodynamic simulations of the combustion process which provide the temperature profiles inside the newly born strange star, we calculate for the first time the neutrino signal that is to be expected if such a conversion process takes place. The neutrino emission is characterized by a luminosity and a duration that is typical for the signal expected from protoneutron stars and represents therefore a powerful source of neutrinos which could be possibly directly detected in case of events occurring close to our Galaxy. We discuss moreover possible connections between the birth of strange stars and explosive phenomena such as supernovae and gamma-ray bursts.

We investigate generic properties of the conformal phase transition in gauge theories featuring Higgs-like fundamental particles. These theories provide an excellent arena to properly investigate conformal dynamics and discover novel features. We show that the phase transition at the boundary of the Higgs conformal window is not smooth but a jumping one for the known perturbative examples. In addition, the general conditions under which the transition is either jumping or smooth are provided. Jumping implies that the massive spectrum of the theory will jump at the phase transition. It, however, still allows for one of the states, the would-be dilaton of the theory, to be lighter than the heaviest states in the broken phase. Finally, we exhibit a calculable Higgs model in which we can, in perturbation theory, determine the Higgs conformal window, the spectrum in the conformally broken phase, and demonstrate it to possess a jumping-type conformal phase transition.

We study the planar-flow distributions of narrow, highly boosted, massive QCD jets. Using the factorization properties of QCD in the collinear limit, we compute the planar-flow jet function from the one-to-three splitting function at tree level. We derive the leading-log behavior of the jet function analytically. We also compare our semianalytic jet function with parton-shower predictions using various generators.

We present a study of the static and dynamical Casimir effects for a quantum field theory satisfying generalized Robin boundary conditions, of a kind that arises naturally within the context of quantum circuits. Since those conditions may also be relevant to measurements of the dynamical Casimir effect, we evaluate their role in the concrete example of a real scalar field in $1+1$ dimensions, a system which has a well-known mechanical analogue involving a loaded string.

The next generation of large scale surveys will not only measure cosmological parameters within the framework of general relativity, but will also allow for precision tests of the framework itself. At the order of linear perturbations, departures from the growth in the standard cosmological model can be quantified in terms of two functions of time and Fourier number $k$. We argue that in local theories of gravity, in the quasistatic approximation, these functions must be ratios of polynomials in $k$, with the numerator of one function being equal to the denominator of the other. Moreover, the polynomials are even and of second degree in practically all viable models considered today. This means that, without significant loss of generality, one can use data to constrain only five functions of a single variable, instead of two functions of two variables. Furthermore, since the five functions are expected to be slowly varying, one can fit them to data in a nonparametric way with the aid of an explicit smoothness prior. We discuss practical application of this parametrization to forecasts and fits.

We construct the holonomy-flux operator algebra in the recently developed spinor formulation of loop gravity. We show that, when restricting to SU(2)-gauge invariant operators, the familiar grasping and Wilson loop operators are written as composite operators built from the gauge-invariant “generalized ladder operators” recently introduced in the $\mathrm{U}(N)$ approach to intertwiners and spin networks. We comment on quantization ambiguities that appear in the definition of the holonomy operator and use these ambiguities as a toy model to test a class of quantization ambiguities which is present in the standard regularization and definition of the Hamiltonian constraint operator in loop quantum gravity.

We study conformally invariant theories of gravity in six dimensions. In four dimensions, there is a unique such theory that is polynomial in the curvature and its derivatives, namely, Weyl-squared, and furthermore all solutions of Einstein gravity are also solutions of the conformal theory. By contrast, in six dimensions there are three independent conformally invariant polynomial terms one could consider. There is a unique linear combination (up to overall scale) for which Einstein metrics are also solutions, and this specific theory forms the focus of our attention in this paper. We reduce the equations of motion for the most general spherically symmetric black hole to a single fifth-order differential equation. We obtain the general solution in the form of an infinite series, characterized by five independent parameters, and we show how a finite three-parameter truncation reduces to the already known Schwarzschild-AdS metric and its conformal scaling. We derive general results for the thermodynamics and the first law for the full five-parameter solutions. We also investigate solutions in extended theories coupled to conformally invariant matter, and in addition we derive some general results for conserved charges in cubic-curvature theories in arbitrary dimensions.

Bertrand space-times (BSTs) are static, spherically symmetric solutions of Einstein’s equations, that admit stable, closed orbits. Starting from the fact that to a good approximation, stars in the disc or halo regions of typical galaxies move in such orbits, we propose that, under certain physical assumptions, the dark matter distribution of some low surface brightness galaxies can seed a particular class of BSTs. In the Newtonian limit, it is shown that for flat rotation curves, our proposal leads to an analytic prediction of the Navarro-Frenk-White dark matter profile of Navarro et al. [Astrophys. J. 462, 563 (1996)]. We further show that the dark matter distribution that seeds the BST is described by a two-fluid anisotropic model, and present its analytic solution. A new solution of the Einstein’s equations, with an internal BST and an external Schwarzschild metric, is also constructed.

Depending on the type and arrangement of metastable vacua in the theory, initial conditions in a de Sitter vacuum with arbitrarily large entropy can be compatible with the observed arrow of time, if the causal patch or related measures are used to regulate divergences. An important condition, however, is that the initial vacuum cannot produce observers from rare fluctuations (Boltzmann brains). Here we consider more general initial conditions where multiple vacua have nonzero initial probability. We examine whether the prediction of an arrow of time is destroyed by a small initial admixture of vacua that can produce Boltzmann brains. We identify general criteria and apply them to two nontrivial examples of such initial probability distributions. The Hartle-Hawking state is superexponentially dominated by the vacuum with smallest positive cosmological constant, so one might expect that other initial vacua can be neglected; but in fact, their inclusion drastically narrows the range of theory parameters for which an arrow of time is predicted. The dominant eigenvector of the global rate equation of eternal inflation is dominated by the longest-lived metastable vacuum. If an arrow of time emerges in the single-initial-vacuum approximation, then we find that this conclusion survives the admixture of other initial vacua. By global-local measure duality, this result amounts to a successful consistency test of certain global cutoffs, including light-cone time and scale-factor time.

In previous works, it was shown that the Lagrangians and Hamiltonians of cosmological linear scalar, vector and tensor perturbations of homogeneous and isotropic space-times with flat spatial sections containing a perfect fluid can be put in a simple form through the implementation of canonical transformations and redefinitions of the lapse function, without ever using the background classical equations of motion. In this paper, we generalize this result to general fluids, which includes entropy perturbations, and to arbitrary spacelike hypersurfaces through a new method together with the Faddeev-Jackiw procedure for the constraint reduction. A simple second order Hamiltonian involving the Mukhanov-Sasaki variable is obtained, again without ever using the background equations of motion.

If during inflation the inflaton couples to a “fossil” field—some new scalar, vector, or tensor field—it typically induces a scalar-scalar-fossil bispectrum. Even if the fossil field leaves no direct physical trace after inflation, it gives rise to correlations between different Fourier modes of the curvature or, equivalently, a nonzero curvature trispectrum, but without a curvature bispectrum. Here we quantify the effects of a fossil field on the cosmic microwave background temperature fluctuations in terms of bipolar spherical harmonics (BiPoSHs). The effects of vector and tensor fossils can be distinguished geometrically from those of scalars through the parity of the BiPoSHs they induce. However, the two-dimensional nature of the cosmic microwave background sky does not allow vectors to be distinguished geometrically from tensors. We estimate the detectability of a signal in terms of the scalar-scalar-fossil coupling for scalar, vector, and tensor fossils, assuming a local-type coupling. We comment on a divergence that arises in the quadrupolar BiPoSH from the scalar-scalar-tensor correlation in single-field slow-roll inflation.