We extend the Kim-Nilles-Peloso (KNP) alignment mechanism for natural inflation to models with $N>2$ axions, which obtains super-Planckian effective axion decay constant $f_{\text{eff}}\gg M_{\mathrm{Pl}}$ through an alignment of the anomaly coefficients of multiple axions having sub-Planckian fundamental decay constants $f_0\ll M_{\mathrm{Pl}}$. The original version of the KNP mechanism realized with two axions requires that some of the anomaly coefficients should be of the order of $f_{\text{eff}}/f_0$, which would be uncomfortably large if $f_{\text{eff}}/f_0\gtrsim \mathcal{O}(100)$ as suggested by the recent BICEP2 results. We note that the KNP mechanism can be realized with the anomaly coefficients of $\mathcal{O}(1)$ if the number of axions $N$ is large as $N\ln N\gtrsim 2\ln (f_{\text{eff}}/f_0)$, in which case the effective decay constant can be enhanced as $f_{\text{eff}}/f_0\sim \sqrt{N!}{n}^{N-1}$ for $n$ denoting the typical size of the integer-valued anomaly coefficients. Comparing to the other multiple axion scenario, the $N$-flation scenario which requires $N\sim f_{\text{eff}}^2/f_0^2$, the KNP mechanism has a virtue of not invoking to a too large number of axions, although it requires a specific alignment of the anomaly coefficients, which can be achieved with a probability of $\mathcal{O}(f_0/f_{\text{eff}})$ under a random choice of the anomaly coefficients. We also present a simple model realizing a multiple axion monodromy along the inflaton direction.

By using the cubic spline interpolation method, we reconstruct the shape of the primordial scalar and tensor power spectra from the recently released Planck temperature and BICEP2 polarization cosmic microwave background data. We find that the vanishing scalar index running ($\mathrm{d}{n}_s/\mathrm{d}\ln k$) model is strongly disfavored at more than $3\sigma$ confidence level on the $k=0.0002{\mathrm{Mpc}}^{-1}$ scale. Furthermore, the power-law parametrization gives a blue-tilt tensor spectrum, no matter using only the first five bandpowers $n_t=1.20_{-0.64}^{+0.56}(95\%\mathrm{C}.\mathrm{L}.)$ or the full nine bandpowers $n_t=1.24_{-0.58}^{+0.51}(95\%\mathrm{C}.\mathrm{L}.)$ of BICEP2 data sets. Unlike the large tensor-to-scalar ratio value ($r\sim 0.20$) under the scale-invariant tensor spectrum assumption, our interpolation approach gives $r_{0.002}<0.060(95\%\mathrm{C}.\mathrm{L}.)$ by using the first five bandpowers of BICEP2 data. After comparing the results with/without BICEP2 data, we find that Planck temperature with small tensor amplitude signals and BICEP2 polarization data with large tensor amplitude signals dominate the tensor spectrum reconstruction on the large and small scales, respectively. Hence, the resulting blue tensor tilt actually reflects the tension between Planck and BICEP2 data.

Einstein’s gravity has the exact Newtonian limit as we take the infinite-speed-of-light limit in the zero-shear gauge and the uniform-expansion gauge. Although lacking proper Newtonian gravitational potential, here we show that Newtonian hydrodynamics for density and velocity is also recovered in the comoving gauge using the weak gravity and negligible pressure limits but without using the slow-motion and subhorizon conditions. This curious correspondence, however, is available only for the irrotational fluid.

In this paper we compute the effective Lagrangian of static gravitational fields interacting with thermal fields of generalized electrodynamics at high temperature. We employ the usual Matsubara imaginary-time formalism to obtain a closed form expression to the thermal effective Lagrangian at one-loop and two-loop order, in an arbitrary $\omega$-dimensional spacetime, in which the equivalence between the static hard thermal loops and those with zero external energy momentum is widely explored. Afterwards, the symmetries of the resulting expressions are discussed as well as the presence of the Tolman local temperature.

In this work, we consider the possibility of expanding wormholes in higher dimensions, which is an important ingredient of modern theories of fundamental physics. An important motivation is that nontrivial topological objects such as microscopic wormholes may have been enlarged to macroscopic sizes in an expanding inflationary cosmological background. Since the Ricci scalar is only a function of time in standard cosmological models, we use this property as a simplifying assumption. More specifically, we consider a particular class of wormhole solutions corresponding to the choice of a spatially homogeneous Ricci scalar. The possibility of obtaining solutions with normal and exotic matter is explored and we find a variety of solutions including those in four dimensions that satisfy the null energy condition in specific time intervals. In particular, for five dimensions, we find solutions that satisfy the null energy condition throughout the respective evolution.

Big-bang nucleosynthesis (BBN) relates key cosmological parameters to the primordial abundance of light elements. In this paper, we point out that the recent observations of cosmic microwave background anisotropies by the Planck satellite and by the BICEP2 experiment constrain these parameters with such a high level of accuracy that the primordial deuterium abundance can be inferred with remarkable precision. For a given cosmological model, one can obtain independent information on nuclear processes in the energy range relevant for BBN, which determine the eventual ${}^2\mathrm{H}/\mathrm{H}$ yield. In particular, assuming the standard cosmological model, we show that a combined analysis of Planck data and of recent deuterium abundance measurements in metal-poor damped Lyman-alpha systems provides independent information on the cross section of the radiative capture reaction $d(p,\gamma ){}^3\mathrm{He}$ converting deuterium into helium. Interestingly, the result is higher than the values suggested by a fit of present experimental data in the BBN energy range (10–300 keV), whereas it is in better agreement with ab initio theoretical calculations, based on models for the nuclear electromagnetic current derived from realistic interactions. Due to the correlation between the rate of the above nuclear process and the effective number of neutrinos $N_{\text{eff}}$, the same analysis points out a $N_{\text{eff}}>3$ as well. We show how this observation changes when assuming a nonminimal cosmological scenario. We conclude that further data on the $d(p,\gamma ){}^3\mathrm{He}$ cross section in the few hundred keV range, which can be collected by experiments like LUNA, may either confirm the low value of this rate, or rather give some hint in favor of next-to-minimal cosmological scenarios.

We present a leptogenesis scenario associated with inflationary models involving non-Abelian gauge fields within the standard model (SM) of particle physics. We show that this class of inflationary models generates intrinsic birefringent gravitational waves that following Alexander, Peskin, and Sheikh-Jabbari [Phys. Rev. Lett. 96, 081301 (2006)], through the gravitational chiral anomaly in the SM, can naturally create a net lepton number density. The $CP$-violating interaction is produced by tensor fluctuations of the gauge field, while the efficiency of this process is determined by the effective background value of the gauge field. We demonstrate that this mechanism can create the observed value of baryon to photon number density in a natural range of parameters of these models.

With the couplings between the eight gluons constrained by the structure constants of the su(3) algebra in QCD, one would expect that there should exist a special basis (or set of bases) for the algebra wherein, unlike in a Cartan-Weyl basis, all gluons interact identically (cyclically) with each other, explicitly on an equal footing. We report here particular such bases, which we have found in a computer search, and we indicate associated $3\times 3$ representations. We conjecture that essentially all cyclic bases for su(3) may be obtained from these making appropriate circulant transformations, and that cyclic bases may also exist for other $\mathrm{su}(n)$, $n>3$.

Apparently convergent contributions of resummed perturbative series at the next-to-leading order of the $1/N$ expansion in the $O(N)$ model are reanalyzed in terms of renormalizability. Compared to our earlier article [G. Fejős et al., Phys. Rev. D 80, 025015 (2009)], an additional subtraction is performed. We show numerically that this is indispensable for diminishing the cutoff sensitivity of some integrals below the scale of the Landau pole. Following the method of our earlier article, an improved counterterm Lagrangian is constructed in the two-particle irreducible formalism, with and without the use of an auxiliary field formulation.

We study the scattering of longitudinally polarized $W$ bosons in extensions of the Standard Model where anomalous Higgs couplings to gauge sector and higher-order $\mathcal{O}(p^4)$ operators are considered. These new couplings with respect to the Standard Model should be thought of as the low-energy remnants of some new dynamics involving the electroweak symmetry breaking sector. By imposing unitarity and causality constraints on the $WW$ scattering amplitudes, we find relevant restrictions on the possible values of the new couplings and the presence of new dynamical resonances above 300 GeV. We investigate the properties of these new resonances and their experimental detectability. Custodial symmetry is assumed to be exact throughout, and the calculation avoids using the equivalence theorem as much as possible.

So far spin foam models are hardly understood beyond a few of their basic building blocks. To make progress on this question, we define analogue spin foam models, so-called “spin nets,” for quantum groups $\mathrm{SU}(2{)}_k$ and examine their effective continuum dynamics via tensor network renormalization. In the refinement limit of this coarse-graining procedure, we find a vast nontrivial fixed-point structure beyond the degenerate and the $BF$ phase. In comparison to previous work, we use fixed-point intertwiners, inspired by Reisenberger’s construction principle [M. P. Reisenberger, J. Math. Phys. (N.Y.) 40, 2046 (1999)] and the recent work [B. Dittrich and W. Kaminski, arXiv:1311.1798], as the initial parametrization. In this new parametrization fine-tuning is not required in order to flow to these new fixed points. Encouragingly, each fixed point has an associated extended phase, which allows for the study of phase transitions in the future. Finally we also present an interpretation of spin nets in terms of melonic spin foams. The coarse-graining flow of spin nets can thus be interpreted as describing the effective coupling between two spin foam vertices or space time atoms.

We study the effects of a generalized uncertainty principle on the classical and quantum cosmology of a closed Friedmann universe whose matter content is either a dust or a radiation fluid. More concretely, assuming the existence of a minimal length, we show that the entropy will constitute a Dirac observable. In addition, ’t Hooft conjecture on the cosmological holographic principle is also investigated. We describe how this holographic principle is satisfied for large values of a quantum number, $n$. This occurs when the entropy is computed in terms of the minimal area.

We examine the recent proposal that the anticross-correlation of the scalar and tensor primordial fluctuations reconciles the tension between BICEP2 and Planck observations. We show that unfortunately the contribution from the scalar-tensor correlation to the cosmic microwave background (CMB) temperature power spectrum vanishes once summed over the angular mode $m$ so the tension between BICEP2 and Planck cannot be reconciled. The reason is that one has to use the spin-weighted spherical harmonics when projecting fields with nonzero spins into the CMB sky. These nonzero spin-weighted spherical harmonics are subject to orthogonality conditions when summed over the angular direction, and thus, the desired cross-correlation between the scalar and tensor perturbations in CMB map vanishes.

The standard perturbative effective potential suffers from two related problems of principle involving the field-dependent Goldstone boson squared mass, $G$. First, in general $G$ can be negative, and it actually is negative in the Standard Model; this leads to imaginary contributions to the effective potential that are not associated with a physical instability, and therefore spurious. Second, in the limit that $G$ approaches zero, the effective potential minimization condition is logarithmically divergent already at two-loop order, and has increasingly severe power-law singularities at higher loop orders. I resolve both issues by resumming the Goldstone boson contributions to the effective potential. For the resulting resummed effective potential, the minimum value and the minimization condition that gives the vacuum expectation value are obtained in forms that do not involve $G$ at all.

Using the Polyakov–Nambu–Jona-Lasinio model the strange quark chiral phase transition and the effect of its current mass on a hot magnetized three flavor quark matter at zero chemical potential is investigated. The impact of the ’t Hooft mixing term on the restoration of the chiral symmetry on the light and strange sectors is studied and the critical temperature dependence on the magnetic field strength of the chiral strange transition is analyzed. It is shown that the $s$ quark is much less sensitive to the magnetic field than the light quarks. Due to the ’t Hooft term, it has a strong influence on the light quarks at all temperatures for small magnetic fields and for temperatures close to the transition temperature at zero magnetic field and above for strong magnetic fields. In particular, the large mass of the $s$ quark makes the chiral transition of the light sector smoother and shifted to larger temperatures. A scalar coupling that weakens when the magnetic field increases will originate an inverse magnetic catalysis also in the $s$ quark and smoothen the signature of the crossover on thermodynamical quantities such as the sound velocities or the specific heat.

The existence of $R$-parity in supersymmetric models can be naturally explained as being a discrete subgroup of gauged baryon minus lepton number ($B-L$). The most minimal supersymmetric $B-L$ model triggers spontaneous $R$-parity violation, while remaining consistent with proton stability. This model is well motivated by string theory and makes several interesting, testable predictions. Furthermore, $R$-parity violation contributes to neutrino masses, thereby connecting the neutrino sector to the decay of the lightest supersymmetric particle (LSP). This paper analyzes the decays of third generation squark LSPs into a quark and a lepton. In certain cases, the branching ratios into charged leptons reveal information about the neutrino mass hierarchy, a current goal of experimental neutrino physics, as well as the ${\theta }_{23}$ neutrino mixing angle. Furthermore, optimization of leptoquark searches for this scenario is discussed. Using currently available data, the lower bounds on the third generation squarks are computed.

Supersymmetric extensions of the standard model lead to gauge/Brout-Englert-Higgs (BEH) unification by providing spin-0 bosons as extra states for spin-1 gauge bosons within massive gauge multiplets. They may be described by the spin-0 components of massive gauge superfields (instead of chiral superfields as usual). In particular, the $125\mathrm{GeV}/c^2$ boson observed at CERN, considered as a BEH boson associated with electroweak breaking and mass generation, may also be interpreted, up to a mixing angle induced by supersymmetry breaking, as the spin-0 partner of the $Z$ under two supersymmetry transformations, i.e., as a $Z$ that would be deprived of its spin.

We apply the Schrödinger functional method to the Abelian gauge theory in three dimensions with $N_f=2$ four-component fermions. We find that the calculated beta function does not cross zero in the range of coupling we study. This implies that the theory exhibits confinement and mass generation, rather than a conformal infrared regime.