We study the Hamiltonian formulation of the generally covariant theory defined by the Lagrangian 4-form $\mathcal{L}=e_I\wedge e_J\wedge F^{IJ}(\omega )$, where $e^I$ is a tetrad field and $F^{IJ}$ is the curvature of a Lorentz connection ${\omega }^{IJ}$. This theory can be thought of as the limit of the Holst action for gravity for the Newton constant $G\to \infty$ and Immirzi parameter $\gamma \to 0$, while keeping the product $G\gamma$ fixed. This theory has for a long time been conjectured to be topological. We prove this statement both in the covariant phase space formulation as well as in the standard Dirac formulation. In the time gauge, the unconstrained phase space of theory admits an $SU(2)$ connection formulation which makes it isomorphic to the unconstrained phase space of gravity in terms of Ashtekar-Barbero variables. Among possible physical applications, we argue that the quantization of this topological theory might shed new light on the nature of the degrees of freedom that are responsible for black entropy in loop quantum gravity.

We consider here a spherically symmetric but inhomogeneous universe filled with a massless scalar field. The model obeys two constraints. The first one is that the gradient of the scalar field is timelike everywhere. The second constraint is that the radial coordinate basis vector is a unit vector field in the comoving coordinate system. We find that the resultant dynamical solutions compose a one-parameter family of self-similar models which is known as the Roberts solution. The solutions are divided into three classes. The first class consists of solutions with only one spacelike singularity in the synchronous-comoving chart. The second class consists of solutions with two singularities which are null and spacelike, respectively. The third class consists of solutions with two spacelike singularities which correspond to the big bang and big crunch, respectively. We see that, in the first case, a comoving volume exponentially expands as in an inflationary period; the fluid elements are accelerated outwards from the symmetry center, even though the strong energy condition is satisfied. This behavior is very different from that observed in the homogeneous and isotropic universe in which the fluid elements would move outwards with deceleration, if the strong energy conditions are satisfied. We are thus able to achieve the accelerated expansion of the universe for the models considered here, without a need to violate the energy conditions. The cosmological features of the models are examined in some detail.

We study structure formation in the presence of primordial non-Gaussianity of the local type with parameters $f_{\mathrm{NL}}$ and $g_{\mathrm{NL}}$. We show that the distribution of dark-matter halos is naturally described by a multivariate bias scheme where the halo overdensity depends not only on the underlying matter density fluctuation $\delta$ but also on the Gaussian part of the primordial gravitational potential $\phi$. This corresponds to a non-local bias scheme in terms of $\delta$ only. We derive the coefficients of the bias expansion as a function of the halo mass by applying the peak-background split to common parametrizations for the halo mass function in the non-Gaussian scenario. We then compute the halo power spectrum and halo-matter cross spectrum in the framework of Eulerian perturbation theory up to third order. Comparing our results against $N$-body simulations, we find that our model accurately describes the numerical data for wave numbers $k\le 0.1–0.3h{\mathrm{Mpc}}^{-1}$ depending on redshift and halo mass. In our multivariate approach, perturbations in the halo counts trace $\phi$ on large scales, and this explains why the halo and matter power spectra show different asymptotic trends for $k\to 0$. This strongly scale-dependent bias originates from terms at leading order in our expansion. This is different from what happens using the standard univariate local bias where the scale-dependent terms come from badly behaved higher-order corrections. On the other hand, our biasing scheme reduces to the usual local bias on smaller scales, where $|\phi |$ is typically much smaller than the density perturbations. We finally discuss the halo bispectrum in the context of multivariate biasing and show that, due to its strong scale and shape dependence, it is a powerful tool for the detection of primordial non-Gaussianity from future galaxy surveys.

This paper reports an experimental demonstration of partial displacement noise free laser interferometry in the gravitational wave detection band. The used detuned Fabry-Perot cavity allows the isolation of the mimicked gravitational wave signal from the displacement noise on the cavities input mirror. By properly combining the reflected and transmitted signals from the cavity a reduction of the displacement noise was achieved. Our results represent the first experimental demonstration of this recently proposed displacement noise free laser interferometry scheme. Overall, we show that the rejection ratio of the displacement noise to the gravitational wave signal was improved in the frequency range of 10 Hz to 10 kHz with a typical factor of $\sim 60$.

Taking into account the $\Lambda$ baryon distribution amplitudes and the most general form of the interpolating current of the ${\Lambda }_b$, the semileptonic ${\Lambda }_b\to \Lambda {\ell }^{+}{\ell }^{-}$ transition is investigated in the framework of the light cone QCD sum rules. Sum rules for all 12 form factors responsible for the ${\Lambda }_b\to \Lambda {\ell }^{+}{\ell }^{-}$ decay are constructed. The obtained results for the form factors are used to compute the branching fraction. A comparison of the obtained results with the existing predictions of the heavy quark effective theory is presented. The results of the branching ratio shows the detectability of this channel at the Large Hadron Collider beauty in the near future is quite high.

Charged Higgs boson may be produced at hadron colliders via the decay of top quarks. At the LHC, the large production cross section of top quarks pairs will make it one of the earliest channels allowing to search for physics beyond the standard model. Assuming the decay $H^{+}\to {\tau }^{+}\nu$, previous searches have so far considered only hadronic $\tau$ decays. Here, we show that by using appropriate kinematical variables (transverse mass observables), leptonic $\tau$ decays can be used as well, for both observing and possibly measuring the mass of the charged Higgs boson. This can increase the overall experimental sensitivity to charged Higgs bosons at hadron colliders.

We report measurements of the branching fractions of neutral and charged $B$ meson decays to final states containing a $K_1(1270)$ or $K_1(1400)$ meson and a charged pion. The data, collected with the BABAR detector at the SLAC National Accelerator Laboratory, correspond to $454\times {10}^6$ $B\overline{B}$ pairs produced in $e^{+}{e}^{-}$ annihilation. We measure the branching fractions $\mathcal{B}(B^0\to K_1(1270{)}^{+}{\pi }^{-}+K_1(1400{)}^{+}{\pi }^{-})={3.1}_{-0.7}^{+0.8}\times {10}^{-5}$ and $\mathcal{B}(B^{+}\to K_1(1270{)}^0{\pi }^{+}+K_1(1400{)}^0{\pi }^{+})={2.9}_{-1.7}^{+2.9}\times {10}^{-5}$ ($<8.2\times {10}^{-5}$ at 90% confidence level), where the errors are statistical and systematic combined. The $B^0$ decay mode is observed with a significance of $7.5\sigma$, while a significance of $3.2\sigma$ is obtained for the $B^{+}$ decay mode. Based on these results, we estimate the weak phase $\alpha =(79\pm 7\pm 11)°$ from the time-dependent $CP$ asymmetries in $B^0\to a_1(1260{)}^{\pm }{\pi }^{\mp }$ decays.

We discuss a twofold extension of QED assuming the presence of strong external fields provided by an ultraintense laser and noncommutativity of spacetime. While noncommutative effects leave the electron’s intensity induced mass shift unchanged, photons change significantly in character: they acquire a quasimomentum that is no longer lightlike. We study the consequences of this combined noncommutative strong-field effect for the basic lepton-photon interactions.

Field theories with spontaneous Lorentz violation involving an antisymmetric 2-tensor are studied. A general action including nonminimal gravitational couplings is constructed, and features of the Nambu-Goldstone and massive modes are discussed. Minimal models in Minkowski spacetime exhibit dualities with Lorentz-violating vector and scalar theories. The post-Newtonian expansion for nonminimal models in Riemann spacetime involves qualitatively new features, including the absence of an isotropic limit. Certain interactions producing stable Lorentz-violating theories in Minkowski spacetime solve the renormalization-group equations in the tadpole approximation.

We have applied a fully relativistic Coulomb wave correction to the weak reactions in the full Kawano/Wagoner big bang nucleosynthesis (BBN) code. We have also added the zero-temperature radiative correction. We find that using this higher accuracy Coulomb correction results in good agreement with previous work, giving only a modest $\sim 0.04\%$ increase in helium mass fraction over correction prescriptions applied previously in BBN calculations. We have calculated the effect of these corrections on other light element abundance yields in BBN, and we have studied these yields as functions of electron neutrino lepton number. This has allowed insights into the role of the weak neutron-proton interconversion processes in the setting of the neutron-to-proton ratio during the BBN epoch. We find that the lepton capture processes’ contributions to this ratio are only second order in the Coulomb correction.

Quasiconstant external fields in nonlinear electromagnetism generate a global contribution proportional to $g^{\mu \nu }$ in the energy-momentum tensor, thus a simulacrum of dark energy. To provide a thorough understanding of the origin and strength of its effects, we undertake a complete theoretical and numerical study of the energy-momentum tensor $T^{\mu \nu }$ for nonlinear electromagnetism. The Euler-Heisenberg nonlinearity due to quantum fluctuations of spinor and scalar matter fields is considered and contrasted with the properties of classical nonlinear Born-Infeld electromagnetism. We address modifications of charged particle kinematics by strong background fields.

In usual particle models, sterile neutrinos can account for the dark matter of the Universe only if they have masses in the keV range and are warm dark matter. Stringent cosmological and astrophysical bounds, in particular, imposed by x-ray observations, apply to them. We point out that in a particular variation of the inert doublet model, sterile neutrinos can account for the dark matter in the Universe and may be either cold or warm dark matter candidates, even for masses much above the keV range. These inert-sterile neutrinos, produced nonthermally in the early Universe, would be stable and have very small couplings to standard model particles, rendering very difficult their detection in either direct or indirect dark matter searches. Their existence could be revealed only by discovering other particles of the model in collider experiments.

We investigate the effects of the nonminimal coupling between the scalar field dark energy (quintessence) and the dark matter on the two-point correlation function. It is well known that this coupling shifts the turnover scale as well as suppresses the amplitude of the matter power spectrum. However, these effects are too small to be observed when we limit the coupling strength to be consistent with observations. Since the coupling of quintessence to baryons is strongly constrained, species-dependent coupling may arise. This results in a baryon bias that is different from unity. Thus, we investigate the correlation function in this coupled model. We are able to observe the enhancement of the baryon acoustic oscillation (BAO) peak due to the increasing bias factor of baryon from this species-dependent coupling. In order to avoid the damping effect of the BAO signature in the matter power spectrum due to nonlinear clustering, we consider the coupling effect on the BAO bump in the linear regime. This provides an alternative method to constrain the coupling of dark energy to dark matter.

The experimental results on the $t\overline{t}$ production cross section at the Tevatron are well described by the QCD contributions within the standard model, while the recently measured forward-backward asymmetry is larger than predicted within this framework. We consider light colored scalars appearing in a particular $SU(5)$ grand unified theory model within the 45-dimensional Higgs representation. A virtue of the model is that it connects the presence of a light colored $SU(2)$ singlet (${\Delta }_6$) and a color octet weak doublet (${\Delta }_1$) with bounds on the proton lifetime, which constrain the parameter space of both scalars. We find that both the total $t\overline{t}$ production cross section and the forward-backward asymmetry can be accommodated simultaneously within this model. The experimental results prefer a region for the mass of ${\Delta }_6$ around 400 GeV, while ${\Delta }_1$ is then constrained to have a mass around the TeV scale as well. We analyze possible experimental signatures and find that ${\Delta }_6$ associated top production could be probed in the $t\overline{t}+\mathrm{\text{jets}}$ final states at Tevatron and the LHC.

We study the collider signatures of the left-right twin Higgs model in the case that the right-handed neutrino mass is less than the mass of the right-handed gauge boson. In this scenario, new leptonic decay chains open up, allowing the particles which cancel the one-loop quadratic divergences of the Higgs, the right-handed gauge bosons and top-partners, to be discovered. Half of these events contain same-sign leptons without missing energy, which have no genuine standard model background and for which the backgrounds are purely instrumental. These signals may be used to complement other collider searches and, in certain regions of parameter space, may be the only way to observe the particles responsible for natural electroweak symmetry breaking in the left-right twin Higgs model.

This paper reports the result of our evaluation of the tenth-order QED correction to the lepton $g-2$ from Feynman diagrams which have sixth-order light-by-light-scattering subdiagrams, none of whose vertices couple to the external magnetic field. The gauge-invariant set of these diagrams, called Set II(e), consists of 180 vertex diagrams. In the case of the electron $g-2$ ($a_e$), where the light-by-light subdiagram consists of the electron loop, the contribution to $a_e$ is found to be $-1.3449(10)(\alpha /\pi {)}^5$. The contribution of the muon loop to $a_e$ is $-0.000465(4)(\alpha /\pi {)}^5$. The contribution of the tau-lepton loop is about two orders of magnitudes smaller than that of the muon loop and hence negligible. The sum of all of these contributions to $a_e$ is $-1.345(1)(\alpha /\pi {)}^5$. We have also evaluated the contribution of Set II(e) to the muon $g-2$ ($a_{\mu }$). The contribution to $a_{\mu }$ from the electron loop is $3.265(12)(\alpha /\pi {)}^5$, while the contribution of the tau-lepton loop is $-0.03806(13)(\alpha /\pi {)}^5$. The total contribution to $a_{\mu }$, which is the sum of these two contributions and the mass-independent part of $a_e$, is $1.882(13)(\alpha /\pi {)}^5$.

Efforts are underway to improve the design and sensitivity of gravitational wave detectors, with the hope that the next generation of these detectors will observe a gravitational wave signal. Such a signal will not only provide information on dynamics in the strong gravity regime that characterizes potential sources of gravitational waves, but will also serve as a decisive test for alternative theories of gravitation that are consistent with all other current experimental observations. We study the linearized theory of the tensor-vector-scalar theory of gravity with generalized vector action, an alternative theory of gravitation designed to explain the apparent deficit of visible matter in galaxies and clusters of galaxies without postulating yet-undetected dark matter. We find the polarization states and propagation speeds for gravitational waves in vacuum, and show that in addition to the usual transverse-traceless propagation modes, there are two more mixed longitudinal-transverse modes and two trace modes, of which at least one has longitudinal polarization. Additionally, the propagation speeds are different from the speed of light.

It is assumed that, for weak space-time curvature, the main gravitational effect of the quantum vacuum stress energy corresponds to adding two terms to the Einstein-Hilbert action, proportional to the square of the curvature scalar and to the contraction of two Ricci tensors, respectively. It is shown that compatibility with terrestrial and Solar System observations implies that the square roots of the coefficients of these terms should be either a few millimeters or a few hundred meters. It is shown that the vacuum contribution increase the stability of massive white dwarfs.

We discuss the essential role of the low-lying eigenmodes of the Faddeev-Popov (FP) ghost operator on the confining color-Coulomb potential using $SU(3)$ quenched lattice simulations in the Coulomb gauge. The color-Coulomb potential is expressed as a spectral sum of the FP ghost operator and has been explored by partially summing the FP eigenmodes. We take into account the Gribov copy effects that have a great impact on the FP eigenvalues and the color-Coulomb potential. We observe that the lowest eigenvalue vanishes in the thermodynamic limit much faster than that in the Landau gauge. The color-Coulomb potential at large distances is governed by the near-zero FP eigenmodes; in particular, the lowest one accounts for a substantial portion of the color-Coulomb string tension comparable to the Wilson string tension.

We study the forward-backward and the $CP$-violating asymmetries (both time independent and time dependent) in rare semileptonic $B_d\to {\rho }^0{\ell }^{+}{\ell }^{-}$, $B_s\to \varphi {\ell }^{+}{\ell }^{-}$, and radiative leptonic $B_{d,s}\to \gamma {\ell }^{+}{\ell }^{-}$ decays and investigate the sensitivity of these asymmetries to the extensions of the standard model.