It was recently shown that a large value of the tensor to scalar ratio $r$ implies a constraint on the minimum value of the sound speed $c_s$ of primordial curvature perturbations during inflation that is stronger than current bounds coming from non-Gaussianity measurements. Here we consider additional aspects related to the measurement of $B$ modes that may provide additional leverage to constrain the sound speed parametrizing noncanonical models of inflation. We find that a confirmation of the consistency relation $r=-8n_t$ between the tensor to scalar ratio $r$ and the tensor spectral index $n_t$ is not enough to rule out noncanonical models of inflation with a sound speed $c_s$ different from unity. To determine whether inflation was canonical or not, one requires knowledge of additional parameters, such as the running of the spectral index of scalar perturbations $\alpha$. We also study how other parameters related to the ultraviolet completion of inflation modify the dependence of $r$ on $c_s$. For instance, we find that heavy degrees of freedom interacting with curvature fluctuations generically tend to make the constraint on the sound speed stronger. Our results, combined with future observations of primordial $B$ modes, may help to constrain the background evolution of noncanonical models of inflation.

We revisit the degeneracy between massive neutrinos and generalized theories of gravity in the framework of the effective field theory of cosmic acceleration. In particular, we consider $f(R)$ theories and a class of nonminimally coupled models parametrized via a coupling to gravity which is linear in the scale factor. In the former case, we find a slightly lower degeneracy with that found in the literature, due to the fact that we implement exact designer $f(R)$ models and evolve the full linear dynamics of perturbations. As a consequence, our bounds are slightly tighter on the $f(R)$ parameter but looser on the summed neutrino mass. We also set a new upper bound on the Compton wavelength parameter ${\text{Log}}_{10}{B}_0<-4.1$ at 95% C.L. with a fixed summed neutrino mass ($\sum m_{\nu }=0.06\mathrm{eV}$) in $f(R)$ gravity with the combined data sets from cosmic microwave background temperature and lensing power spectra of the Planck Collaboration, as well as galaxy power spectrum from the WiggleZ dark energy survey. We do not observe a sizable degeneracy between massive neutrinos and modified gravity in the nonminimally coupled model considered, which corresponds to a peculiar case of coupling that depends linearly on the scale factor. The analysis is performed with an updated version of the eftcamb/EFTCosmoMC package, which is now publicly available and extends the first version of the code with the consistent inclusion of massive neutrinos, tensor modes, several alternative background histories, and designer quintessence models.

In this paper, a specific family of $f(R)$ models that can produce the $\mathrm{\Lambda }\mathrm{CDM}$ background expansion history is constrained by using the currently available geometric and dynamic probes. The scale dependence of the growth rate $f(z,k)$ in this specific family of $f(R)$ model is shown. Therefore to eliminate the scale dependence of $f{\sigma }_8(z)$ in theory, which usually is defined as the product of $f(z,k)$ and ${\sigma }_8(z)$, we define $f{\sigma }_8(z)=d{\sigma }_8(z)/d\ln a$, which is obviously scale independent and reproduces the conventional definition in the standard $\mathrm{\Lambda }\mathrm{CDM}$ cosmology. In doing so, under the assumption that future probes having the same best fit values as the current ten data points of $f{\sigma }_8(z)$, even having 20% error bars enlarged, we find a preliminary constraint $f_{R0}=-2.58_{-0.58}^{+2.14}\times {10}^{-6}$ in $1\sigma$ regions. This indicates the great potential that redshift space distortions have in constraining modified gravity theories. We also discuss the nonlinear matter power spectrum based on different halo fit models.

We discuss diffractive production of open charm and bottom mesons at the LHC. The differential cross sections for single- and central-diffractive mechanisms for $c\overline{c}$ and $b\overline{b}$ pair production are calculated in the framework of the Ingelman-Schlein model corrected for absorption effects. In this approach, one assumes that the Pomeron has a well-defined partonic structure, and that the hard process takes place in a Pomeron-proton or proton-Pomeron (single diffraction) or Pomeron-Pomeron (central diffraction) process. Here, leading-order gluon-gluon fusion and quark-antiquark annihilation partonic subprocesses are taken into consideration, which are calculated within standard collinear approximation. Both Pomeron flux factors as well as parton distributions in the Pomeron are taken from the H1 Collaboration analysis of diffractive structure function and diffractive dijets at HERA. The extra corrections from subleading Reggeon exchanges are explicitly calculated and are also taken into consideration. Several quark-level differential distributions are shown. The hadronization of charm and bottom quarks is taken into account by means of fragmentation function technique. Predictions for single- and central-diffractive production in the case of inclusive $D$ and $B$ mesons, as well as $D\overline{D}$ pairs, are presented, including detector acceptance of the ATLAS, CMS, and LHCb collaborations. The experimental aspects of possible standard and dedicated measurements are carefully discussed.

Based on a sample of $2.25\times {10}^{8}J/\psi$ events taken with the BESIII detector at the BEPCII collider, we present the results of a study of the decay $J/\psi \to \eta \varphi {\pi }^{+}{\pi }^{-}$. The $Y(2175)$ resonance is observed in the invariant mass spectrum of $\varphi f_0(980)$ with a statistical significance of greater than $10\sigma$. The corresponding mass and width are determined to be $M=2200\pm 6(\mathrm{stat})\pm 5(\mathrm{syst})\mathrm{MeV}/c^2$ and $\mathrm{\Gamma }=104\pm 15(\mathrm{stat})\pm 15(\mathrm{syst})\mathrm{MeV}$, respectively, and the product branching fraction is measured to be $\mathcal{B}(J/\psi \to \eta Y(2175),Y(2175)\to \varphi f_0(980),f_0(980)\to {\pi }^{+}{\pi }^{-})=(1.20\pm 0.14(\mathrm{stat})\pm 0.37(\mathrm{syst}))\times {10}^{-4}$. The results are consistent within errors with those of previous experiments. We also measure the branching fraction of $J/\psi \to \varphi f_1(1285)$ with $f_1(1285)\to \eta {\pi }^{+}{\pi }^{-}$ and set upper limits on the branching fractions for $J/\psi \to \varphi \eta (1405)/\varphi X(1835)/\varphi X(1870)$ with $\eta (1405)/X(1835)/X(1870)\to \eta {\pi }^{+}{\pi }^{-}$ at the 90% confidence level.

The scalar strangeness content of the nucleon, characterized by the so-called strangeness-nucleon sigma term, is of fundamental importance in understanding its sea-quark flavor structure. We report a determination of the octet baryon sigma terms via the Feynman-Hellmann theorem by analyzing the latest high-statistics $n_f=2+1$ lattice QCD simulations with covariant baryon chiral perturbation theory up to next-to-next-to-next-to-leading order. In particular, we predict ${\sigma }_{\pi N}=55(1)(4)\mathrm{MeV}$ and ${\sigma }_{sN}=27(27)(4)\mathrm{MeV}$, while the first error is statistical and the second systematic due to different lattice scales. The predicted ${\sigma }_{sN}$ is consistent with the latest LQCD results and the results based on the next-to-next-to-leading order chiral perturbation theory. Several key factors in determining the sigma terms are systematically taken into account and clarified for the first time, including the effects of lattice scale setting, systematic uncertainties originating from chiral expansion truncations, and constraint of strong-interaction isospin breaking effects.

We propose a possibility to improve the current precision measurements on compact binaries. When the orbital axis is almost perpendicular to our line of sight, a pulsar behind its companion can form two strong lensing images. These images cannot be resolved, but we can use multiwavelength interferometry to accurately determine the passage through superior conjunction. This method does not depend strongly on the stability of the pulse profile and applies equally well to both slow and fast pulsars. We discuss the possible improvement this can bring to the bound on stochastic gravitational wave background and to determine black hole spin. We also discuss the possibility of discovering a suitable binary system by the Square Kilometer Array to which our method can apply.

We study the canonical structure of the real first order formulation of general relativity on a null foliation. We use a tetrad decomposition which allows us to elegantly encode the nature of the foliation in the norm of a vector in the fiber bundle. The resulting constraint structure shows some peculiarities. In particular, the dynamical Einstein equations propagating the physical degrees of freedom appear in this formalism as second class tertiary constraints, which puts them on the same footing as the Hamiltonian constraint of Ashtekar’s connection formulation. We also provide a framework to address the issue of zero modes in gravity, in particular, to study the nonperturbative fate of the zero modes of the linearized theory. Our results give a new angle on the dynamics of general relativity and can be used to quantize null hypersurfaces in the formalism of loop quantum gravity or spin foams.

We study the four-dimensional Universe on the M2-M5 BIon in the thermal background. The BIon is a configuration in a flat space of a D-brane and a parallel anti-D-brane connected by a wormhole. When the branes and antibranes are well separated and the brane’s spike is far from the antibrane’s spike, the wormhole cannot be formed. However, when two branes are close to each other, they can be connected by a wormhole. Under this condition, there exist many channels for flowing energy from extra dimensions into our Universe. This energy dominates all other forms of energy, such as the gravitational repulsion, and brings our brief epoch of the Universe to an end in the big rip singularity. We show that at this singularity the Universe is destroyed, and one black M2-brane is formed. Finally, we test our model against WMAP, Planck, and BICEP2 data, and we obtain the ripping time. According to experimental data, the $N\simeq 50$ case leads to $n_s\simeq 0.96$, where $N$ and $n_s$ are the number $e$-folds and the spectral index, respectively. This standard case may be found in $0.01<R_{\text{Tensor-scalar}}<0.3$, where $R_{\text{Tensor-scalar}}$ is the tensor-to-scalar ratio. At this point, the big rip singularity occurs in a finite time $t_{\text{rip}}=31(\mathrm{Gyr})$ for WMAP and Planck data and $t_{\text{rip}}=28(\mathrm{Gyr})$ for BICEP2 data. By comparing this time with the time of the big rip in the brane-antibrane, we find that the wormhole in the BIonic system accelerates the destruction of the Universe.

A fine set of parameters is introduced for bouncing cosmologies in order to describe the nearly matter-dominated phase, and which play the same role that the usual slow-roll parameters play in inflationary cosmology. It is shown that, as in the inflation case, the spectral index and the running parameter for scalar perturbations in bouncing cosmologies can be best expressed in terms of these small parameters. Further, they explicitly exhibit the duality that exists between a nearly matter-dominated universe in its contracting phase and the quasi–de Sitter regime in the expanding one. The results obtained also confirm and extend the known evidence that the spectral index for an exactly matter-dominated universe (i.e., a pressureless universe) in the contracting phase is, in fact, the same as the spectral index for an exact de Sitter regime in the expanding phase. Finally, in both the inflationary and the matter bounce scenarios, the theoretical values of the spectral index and of the running parameter are compared with their experimental counterparts, obtained from the most recent Planck data, with the result that the bouncing models discussed here fit accurate astronomical observations well.

We consider a deformed single-field inflation model in terms of three SO(3) symmetric moduli fields. We find that spatially linear solutions for the moduli fields induce a phase transition during the early stage of the inflation and the suppression of scalar power spectrum at large scales. This suppression can be an origin of anomalies for large-scale perturbation modes in the cosmological observation.

We consider a massive scalar field with quartic self-interaction $\lambda /4!{\varphi }^4$ in de Sitter spacetime and present a diagrammatic expansion that describes the field as driven by stochastic noise. This is compared with the Feynman diagrams in the Keldysh basis of the amphichronous (closed-time-path) field theoretical formalism. For all orders in the expansion, we find that the diagrams agree when evaluated in the leading infrared approximation, i.e. to leading order in $m^2/H^2$, where $m$ is the mass of the scalar field and $H$ is the Hubble rate. As a consequence, the correlation functions computed in both approaches also agree to leading infrared order. This perturbative correspondence shows that the stochastic theory is exactly equivalent to the field theory in the infrared. The former can then offer a nonperturbative resummation of the field theoretical Feynman diagram expansion, including fields with $0\le m^2\ll \sqrt{\lambda }{H}^2$ for which the perturbation expansion fails at late times.

Isolated pulsars are rotating neutron stars with accurately measured angular velocities $\mathrm{\Omega }$, and their time derivatives that show unambiguously that the pulsars are slowing down. Although the exact mechanism of the spin-down is a question of detailed debate, the commonly accepted view is that it arises through emission of magnetic dipole radiation (MDR) from a rotating magnetized body. Other processes, including the emission of gravitational radiation, and of relativistic particles (pulsar wind), are also being considered. The calculated energy loss by a rotating pulsar with a constant moment of inertia is assumed proportional to a model dependent power of $\mathrm{\Omega }$. This relation leads to the power law $\dot{\mathrm{\Omega }}=-K{\mathrm{\Omega }}^n$ where $n$ is called the braking index. The MDR model predicts $n$ exactly equal to 3. Selected observations of isolated pulsars provide rather precise values of $n$, individually accurate to a few percent or better, in the range $1<n<2.8$, which is consistently less than the predictions of the MDR model. In spite of an extensive investigation of various modifications of the MDR model, no satisfactory explanation of observation has been found yet. The aim of this work is to determine the deviation of the value of $n$ from the canonical $n=3$ for a star with a frequency dependent moment of inertia in the region of frequencies from zero (static spherical star) to the Kepler velocity (onset of mass shedding by a rotating deformed star), in the macroscopic MDR model. For the first time, we use microscopic realistic equations of state (EoS) of the star to determine its behavior and structure. In addition, we examine the effects of the baryonic mass $M_B$ of the star, and possible core superfluidity, on the value of the braking index within the MDR model. Four microscopic equations of state are employed as input to two different computational codes that solve Einstein’s equations numerically, either exactly or using the perturbative Hartle-Thorne method, to calculate the moment of inertia and other macroscopic properties of rotating neutron stars. The calculations are performed for fixed values of $M_B$ (as masses of isolated pulsars are not known) ranging from $1.0–2.2M_{\odot }$, and fixed magnetic dipole moment and inclination angle between the rotational and magnetic field axes. The results are used to solve for the value of the braking index as a function of frequency, and find the effect of the choice of the EoS, $M_B$. The density profile of a star with a given $M_B$ is calculated to determine the transition between the crust and the core and used in estimation of the effect of core superfluidity on the braking index. Our results show conclusively that, within the model used in this work, any significant deviation of the braking index away from the value $n=3$ occurs at frequencies higher than about ten times the frequency of the slow rotating isolated pulsars most accurately measured to date. The rate of change of $n$ with frequency is related to the softness of the EoS and the $M_B$ of the star as this controls the degree of departure from sphericity. Change in the moment of inertia in the MDR model alone, even with the more realistic features considered here, cannot explain the observational data on the braking index and other mechanisms have to be sought.

Electrically neutral massive color-singlet and color-octet vector bosons, which are often predicted in theories beyond the Standard Model, have the potential to be discovered as dijet resonances at the LHC. A color-singlet resonance that has leptophobic couplings needs further investigation to be distinguished from a color-octet one. In previous work, we introduced a method for discriminating between the two kinds of resonances when their couplings are flavor universal, using measurements of the dijet resonance mass, total decay width, and production cross section. Here, we describe an extension of that method to cover a more general scenario, in which the vector resonances could have flavor-nonuniversal couplings; essentially, we incorporate measurements of the heavy-flavor decays of the resonance into the method. We present our analysis in a model-independent manner for a dijet resonance with mass 2.5–6.0 TeV at the LHC with $\sqrt{s}=14\mathrm{TeV}$ and integrated luminosities of 30, 100, 300, and $1000{\mathrm{fb}}^{-1}$ and show that the measurements of the heavy-flavor decays should allow conclusive identification of the vector boson. Note that our method is generally applicable even for a $Z^{\prime }$ boson with non-Standard invisible decays. We include an Appendix of results for various resonance couplings and masses to illustrate how well each observable must be measured to distinguish colorons from $Z^{\prime }\mathrm{s}$.

We present a search for the rare leptonic decays $B^{+}\to e^{+}{\nu }_e$ and $B^{+}\to {\mu }^{+}{\nu }_{\mu }$, using the full $\mathrm{\Upsilon }(4S)$ data sample of $772\times 10^6$ $B\overline{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. One of the $B$ mesons from the $\mathrm{\Upsilon }(4S)\to B\overline{B}$ decay is fully reconstructed in a hadronic mode, while the recoiling side is analyzed for the signal decay. We find no evidence of a signal in any of the decay modes. Upper limits of the corresponding branching fractions are determined as $\mathcal{B}(B^{+}\to e^{+}{\nu }_e)<3.5\times 10^{-6}$ and $\mathcal{B}(B^{+}\to {\mu }^{+}{\nu }_{\mu })<2.7\times 10^{-6}$ at 90% confidence level.

Next-generation long-baseline electron neutrino appearance experiments will seek to discover $CP$ violation, determine the mass hierarchy and resolve the ${\theta }_{23}$ octant. In light of the recent precision measurements of ${\theta }_{13}$, we consider the sensitivity of these measurements in a study to determine the optimal baseline, including practical considerations regarding beam and detector performance. We conclude that a detector at a baseline of at least 1000 km in a wide-band muon neutrino beam is the optimal configuration.

Single-beam, single-target, and double spin asymmetries for hard exclusive electroproduction of a photon on the proton $\overrightarrow{e}\overrightarrow{p}\to e^{\prime }{p}^{\prime }\gamma$ are presented. The data were taken at Jefferson Lab using the CEBAF large acceptance spectrometer and a longitudinally polarized ${}^{14}{\mathrm{NH}}_3$ target. The three asymmetries were measured in 165 four-dimensional kinematic bins, covering the widest kinematic range ever explored simultaneously for beam and target-polarization observables in the valence quark region. The kinematic dependences of the obtained asymmetries are discussed and compared to the predictions of models of generalized parton distributions. The measurement of three DVCS spin observables at the same kinematic points allows a quasi-model-independent extraction of the imaginary parts of the $H$ and $\tilde{H}$ Compton form factors, which give insight into the electric and axial charge distributions of valence quarks in the proton.

We construct a wide class of nongeometric compactifications of type II superstring theories preserving $\mathrm{N}=1$ space-time supersymmetry in four dimensions, starting from Calabi-Yau compactifications at Gepner points. Particular examples of this construction provide quantum equivalences between Calabi-Yau compactifications and non-Calabi-Yau ones, generalizing mirror symmetry. The associated Landau-Ginzburg models involve both chiral and twisted chiral multiplets and hence cannot be lifted to ordinary Calabi-Yau gauged linear sigma models.

Building on an analogy with ordinary scalar field theories, an $ϵ$-expansion for rank-3 tensorial group field theories with gauge invariance condition is introduced. This allows us to continuously interpolate between the dimension four group $\mathrm{SU}(2)\times \mathrm{U}(1)$ and the dimension three SU(2). In the first situation, there is a unique marginal ${\phi }^4$ coupling constant, but in contrast to ordinary scalar field theory this model is asymptotically free. In the SU(2) case, the presence of two marginally relevant ${\phi }^6$ coupling constants and one ${\phi }^4$ super-renormalizable interaction spoils this interesting property. However, the existence of a nontrivial fixed point is established in dimension $4-ϵ$, hence suggesting that the SU(2) theory might be asymptotically safe. To pave the way to future nonperturbative calculations, the present perturbative results are discussed in the framework of the effective average action.

The common tunneling picture of electron-positron pair creation in a strong electric field is generalized to pair creation in combined crossed electric and magnetic fields. This enhanced picture, being symmetric for electrons and positrons, is formulated in a gauge-invariant and Lorentz-invariant manner for quasistatic fields. It may be used to infer qualitative features of the pair creation process. In particular, it allows for an intuitive interpretation of how the presence of a magnetic field modifies and, in particular cases, even enhances pair creation. The creation of electrons and positrons from the vacuum may be assisted by an energetic photon, which can also be incorporated into this picture of pair creation.