Chameleon fields, which are scalar field dark energy candidates, can evade fifth force constraints by becoming massive in high-density regions. However, this property allows chameleon particles to be trapped inside a vacuum chamber with dense walls. Afterglow experiments constrain photon-coupled chameleon fields by attempting to produce and trap chameleon particles inside such a vacuum chamber, from which they will emit an afterglow as they regenerate photons. Here we discuss several theoretical and systematic effects underlying the design and analysis of the GammeV and CHASE afterglow experiments. We consider chameleon particle interactions with photons, Fermions, and other chameleon particles, as well as with macroscopic magnetic fields and matter. The afterglow signal in each experiment is predicted, and its sensitivity to various properties of the experimental apparatus is studied. Finally, we use CHASE data to exclude a wide range of photon-coupled chameleon dark energy models.

The observation of earth skimming neutrinos has been proposed as a rather sensitive method to detect ultra-high energy (UHE) cosmic neutrinos. Energetic cosmic neutrinos can interact inside the rock and produce leptons via a charged current interaction. In the case of an incoming ${\nu }_e$ undergoing a charged current interaction, the produced UHE electron will induce an underground electromagnetic shower. At high energy (above 7.7 TeV in standard rock), such showers are subject to LPM (Landau, Pomeranchuk, and Migdal) suppression of the radiative processes cross sections (bremsstrahlung and pair production). The consequence of this suppression is that showers are elongated. This effect will increase the detection probability of such events allowing deeper showers to emerge with detectable energies. On the other hand, the photonuclear processes which are usually neglected in electromagnetic showers with respect to radiative processes, turn out to become dominant in the LPM regime and will reduce the shower length. In this work, we have performed a complete Monte Carlo study of an underground shower induced by UHE electrons by taking into account both the LPM suppression and the photonuclear interaction. We will discuss the effects of both of these processes on the shower length and on the detectability of such events by ground arrays or fluorescence telescopes. We show that limits on neutrino fluxes that were obtained using simulations that were obviously neglecting photonuclear processes are overoptimistic and should be corrected.

We report measurements of partial branching fractions for inclusive charmless semileptonic $B$ decays $\overline{B}\to X_u\ell \overline{\nu }$ and the determination of the Cabibbo–Kobayashi–Maskawa (CKM) matrix element $|V_{ub}|$. The analysis is based on a sample of $467\times {10}^6$ ${\rm Y}(4S)\to B\overline{B}$ decays recorded with the BABAR detector at the PEP-II $e^{+}{e}^{-}$ storage rings. We select events in which the decay of one of the $B$ mesons is fully reconstructed and an electron or a muon signals the semileptonic decay of the other $B$ meson. We measure partial branching fractions $\Delta \mathcal{B}$ in several restricted regions of phase space and determine the CKM element $|V_{ub}|$ based on different QCD predictions. For decays with a charged lepton momentum $p_{\ell }^{*}>1.0\mathrm{GeV}$ in the $B$ meson rest frame, we obtain $\Delta \mathcal{B}=(1.80\pm {0.13}_{\mathrm{stat}}\pm {0.15}_{\mathrm{sys}}\pm {0.02}_{\mathrm{theo}})\times {10}^{-3}$ from a fit to the two-dimensional $M_X-q^2$ distribution. Here, $M_X$ refers to the invariant mass of the final state hadron $X$ and $q^2$ is the invariant mass squared of the charged lepton and neutrino. From this measurement we extract $|V_{ub}|=(4.33\pm {0.24}_{\exp }\pm {0.15}_{\mathrm{theo}})\times {10}^{-3}$ as the arithmetic average of four results obtained from four different QCD predictions of the partial rate. We separately determine partial branching fractions for ${\overline{B}}^0$ and $B^{-}$ decays and derive a limit on the isospin breaking in $\overline{B}\to X_u\ell \overline{\nu }$ decays.

We report on a search for the charmless decays $B^{+}\to \varphi {\pi }^{+}$ and $B^0\to \varphi {\pi }^0$ that are strongly suppressed in the standard model. The analysis is based on a data sample of $657\times {10}^6$ $B\overline{B}$ pairs collected at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We find no significant signal and set upper limits of $3.3\times {10}^{-7}$ for $B^{+}\to \varphi {\pi }^{+}$ and $1.5\times {10}^{-7}$ for $B^0\to \varphi {\pi }^0$ at the 90% confidence level.

We analyze if and to what extent the high energy behavior of five-dimensional (5D) gauge theories can be improved by adding certain higher dimensional operators of “Lifshitz” type, without breaking the ordinary four-dimensional Lorentz symmetries. We show that the UV behavior of the transverse gauge field polarizations can be improved by the Lifshitz operators, while the longitudinal polarizations get strongly coupled at energies lower than the ones in ordinary 5D theories, spoiling the usefulness of the construction in non-Abelian gauge theories. We conclude that the improved behavior as effective theories of the ordinary 5D models is not only related to locality and 5D gauge symmetries, but is a special property of the standard theories defined by the lowest dimensional operators.

The degrees of freedom of any interacting quantum field theory are entangled in momentum space. Thus, in the vacuum state, the infrared degrees of freedom are described by a density matrix with an entanglement entropy. We derive a relation between this density matrix and the Wilsonian effective action obtained by integrating out degrees of freedom with spatial momentum above some scale. We argue that the entanglement entropy of and mutual information between subsets of field theoretic degrees of freedom at different momentum scales are natural observables in quantum field theory and demonstrate how to compute these in perturbation theory. The results may be understood heuristically based on the scale dependence of the coupling strength and number of degrees of freedom. We measure the rate at which entanglement between degrees of freedom declines as their scales separate and suggest that this decay is related to the property of decoupling in quantum field theory.

We study static, spherically symmetric solutions with an electric field in an extension of general relativity containing a Ricci-squared term and formulated in the Palatini formalism. We find that all the solutions present a central core whose area is proportional to the Planck area times the number of charges. Far from the core, curvature invariants quickly tend to those of the usual Reissner-Nordström solution, though the structure of horizons may be different. In fact, besides the structures found in the Reissner-Nordström solution of general relativity, we find black hole solutions with just one nondegenerate horizon (Schwarzschild-like) and nonsingular black holes and naked cores. The charge-to-mass ratio of the nonsingular solutions implies that the core matter density is independent of the specific amounts of charge and mass and of order the Planck density. We discuss the physical implications of these results for astrophysical and microscopic black holes, construct the Penrose diagrams of some illustrative cases, and show that the maximal analytical extension of the nonsingular solutions implies a bounce of the radial coordinate.

The low frequency gravitational wave detectors like the evolved Laser Interferometer Space Antenna/New Gravitational Wave Observatory (eLISA/NGO) will give us the opportunity to test whether the supermassive compact objects lying at the centers of galaxies are indeed Kerr black holes. One way to do such a test is to compare the gravitational wave signals with templates of perturbed black hole spacetimes, the so-called bumpy black hole spacetimes. The Zipoy-Voorhees (ZV) spacetime (known also as the $\gamma$ spacetime) can be included in the bumpy black hole family, since it can be considered as a perturbation of the Schwarzschild spacetime background. Several authors have suggested that the ZV metric corresponds to an integrable system. Contrary to this integrability conjecture, the present article shows by numerical examples that, in general, ZV belongs to the family of nonintegrable systems.

The maximum likelihood method is often used for parameter estimation in gravitational wave astronomy. Recently, an interesting approach was proposed by Vallisneri to evaluate the distributions of parameter estimation errors expected for the method. This approach is to statistically analyze the local peaks of the likelihood surface, and works efficiently even for signals with low signal-to-noise ratios. Focusing special attention to geometric structure of the likelihood surface, we follow the proposed approach and derive formulas for a simplified model of data analysis where the target signal has only one intrinsic parameter, along with its overall amplitude. Then we apply our formulas to correlation analysis of stochastic gravitational wave background with a power-law spectrum. We report qualitative trends of the formulas using numerical results specifically obtained for correlation analysis with two Advanced-LIGO detectors.

We investigate the potential of the early LHC to discover the signal of monotops, which can be decay products of some resonances in models such as $R$-parity-violating supersymmetry or SU(5), etc. We show how to constrain the parameter space of the models by the present data of $Z$ boson hadronic decay branching ratio, $K^0\mathrm{\text{−}}{\overline{K}}^0$ mixing and dijet productions at the LHC. Then, we study the various cuts imposed on the events, reconstructed from the hadronic final states, to suppress backgrounds and increase the significance in detail. And we find that in the hadronic mode the information from the missing transverse energy and reconstructed resonance mass distributions can be used to specify the masses of the resonance and the missing particle. Finally, we study the sensitivities to the parameters at the LHC with $\sqrt{s}=7\mathrm{TeV}$ and an integrated luminosity of $1{\mathrm{fb}}^{-1}$ in detail. Our results show that the early LHC may detect this signal at $5\sigma$ level for some regions of the parameter space allowed by the current data.

In this work, we calculate the total cross sections and the center-of-mass frame angular distributions of the charmonium production plus a light meson by the low energy $p\overline{p}$ interaction. The results of $p\overline{p}\to {\pi }^0\Psi$ with and without form factor (FF) indicate that the FF contribution in the calculation cannot be ignored. The obtained cross section of $p\overline{p}\to {\pi }^{0}J/\psi$ with FF can fit the E760 data well. We also predict the total cross sections and the center-of-mass frame angular distributions of $p\overline{p}\to \omega \Psi$, which show that these physical quantities are dependent on Pauli ($g_{\omega }$) and Dirac (${\kappa }_{\omega }$) coupling constants of the $pp\omega$ interaction. Thus, $p\overline{p}\to \omega \Psi$ can be as the ideal channel to test the different theoretical values of $g_{\omega }$ and ${\kappa }_{\omega }$. Applying the formulae of $p\overline{p}\to {\pi }^0\Psi$ and $p\overline{p}\to \omega \Psi$, we predict the total cross sections of the $p\overline{p}\to \eta \Psi$ and $p\overline{p}\to \rho \Psi$ reactions. Our results show a common behavior of the charmonium production with a light meson by the $p\overline{p}$ interaction, where the total cross section of the ${\eta }_c$ production is the largest one among all discussed processes. The above observations can be directly tested at the forthcoming $\overline{\mathrm{P}}\mathrm{ANDA}$ experiment.

In order to significantly raise the mass of the supersymmetry Higgs boson, we consider a radiative correction to it by heavy ($\sim 1\mathrm{TeV}$) hidden sector fields, which communicate with the Higgs through relatively light “messengers” (300–500 GeV). The messenger fields ($S$, $\overline{S}$) are coupled to the Higgs (“$y_{H}S{H}_u{H}_d$,” $y_H\lesssim 0.7$) and also to hidden sector fields with a Yukawa coupling of order unity. The hidden sector fields are assumed to be large representations of a hidden gauge group, and so their scalar partner masses can be heavier than other typical soft scalars in the visible sector. Even with a relatively small $y_H$ ($\sim 0.2$) or $\tan \beta \sim 10$ but without top-stop’s considerable contributions, the radiative correction by such hidden sector fields can be enhanced enough to yield the 125 GeV Higgs mass.

We describe a systematic way of the generalization, to models with nonlinear duality, of the space-time covariant and duality-invariant formulation of duality-symmetric theories in which the covariance of the action is ensured by the presence of a single auxiliary scalar field. It is shown that the duality-symmetric action should be invariant under the two local symmetries characteristic of this approach, which impose constraints on the form of the action similar to those of Gaillard and Zumino and in the noncovariant formalism. We show that the (twisted) self-duality condition obtained from this action upon integrating its equations of motion can always be recast in a manifestly covariant form which is independent of the auxiliary scalar and thus corresponds to the conventional on-shell duality-symmetric covariant description of the same model. Supersymmetrization of this construction is briefly discussed.

By employing special solutions of the Hamilton-Jacobi equation and tools from lattice theories, we suggest an approach to convert classical theories to quantum theories for mechanics and field theories. Some nontrivial results are obtained for a gauge field and a fermion field. For a topologically massive gauge theory, we can obtain a first order Lagrangian with mass term. For the fermion field, in order to make our approach feasible, we supplement the conventional Lagrangian with a surface term. This surface term can also produce the mass term for the fermion.

We study the effect of charge on gravitational collapse of an inhomogeneous dust cloud in the Einstein, Gauss-Bonnet and Lovelock gravity. Dynamics of the collapsing shell is analyzed. The conditions for the occurrence of bounce during collapse are given. We also show that shell crossing occurs inevitably if the shell near the center is weakly charged.

Within the framework of the scalar-tensor theory, its second post-Newtonian (2PN) approximation is obtained with Chandrasekhar’s approach. By focusing on an $N$-point mass system as the first step, we reduce the metric to its 2PN form for light propagation. Unlike previous works, at 2PN order, we abandon the hierarchized hypothesis and do not assume two parametrized post-Newtonian parameters $\gamma$ and $\beta$ to be unity. We find that although there exist $\gamma$ and $\beta$ in the 2PN metric, only $\gamma$ appears in the 2PN equations of light. As a simple example for applications, a gauge-invariant angle between the directions of two incoming photons for a differential measurement is investigated after the light trajectory is solved in a static and spherically symmetric spacetime. It shows the deviation from the general relativity $\delta {\theta }_{\mathrm{STT}}$ does not depend on $\beta$ even at 2PN level in this circumstance, which is consistent with previous results. A more complicated application is light deflection in a 2-point mass system. We consider a case that the light propagation time is much less than the time scale of its orbital motion and thus treat it as a static system. The 2-body effect at 2PN level originating from relaxing the hierarchized hypothesis is calculated. Our analysis shows the 2PN 2-body effect in the Solar System is one order of magnitude less than future $\sim 1\mathrm{nano}\mathrm{\text{−}}\mathrm{arcsecond}$ experiments, while this effect could be comparable with first post-Newtonian component of $\delta {\theta }_{\mathrm{STT}}$ in a binary system with two Sun-like stars and separation by $\sim 0.1\mathrm{AU}$ if an experiment would be able to measure $\gamma -1$ down to $\sim {10}^{-6}$.

The bi-tensor kernel in the integral form of Einstein equations realizing Mach’s idea of nonexistence of empty space-times is taken as an inverse of the differential operator (”Mach operator”) defined conventionally as a second variation of Einstein’s gravity action over contravariant components of the metric tensor. The choice of transverse gauge condition used in this definition does not influence results of the paper since only transverse and traceless tensor modes written on different background space-times are studied. The presence of ghosts among modes of the Mach operator invalidates the integral formulation of Einstein equations. And the demand of the absence of these ghosts proves to be a selection rule for dimensionality of the background space-time. In particular, the Mach operator written on the De Sitter background or on the background of the so-called “Einstein Universe” does not possess tensor ghosts only in four dimensions. The similar demand gives a nontrivial formula for dimensionalities of subspaces of the Freund–Rubin background.

In this paper we study perturbatively an extension of the Stelle higher derivative gravity involving an infinite number of derivative terms. We know that the usual quadratic action is renormalizable but suffers from the unitarity problem because of the presence of a ghost (state of negative norm) in the theory. In this paper, we reconsider the theory first introduced by Tomboulis in 1997, but we expand and extensively study it at both the classical and quantum level. This theory is ghost-free, since the introduction of (in general) two entire functions in the model with the property does not introduce new poles in the propagator. The local high derivative theory is recovered expanding the entire functions to the lowest order in the mass scale of the theory. Any truncation of the entire functions gives rise to the unitarity violation, but if we keep all the infinite series, we do not fall into these troubles. The theory is renormalizable at one loop and finite from two loops on. Since only one-loop Feynman diagrams are divergent, then the theory is super-renormalizable. We analyze the fractal properties of the theory at high energy showing a reduction of the spacetime dimension at short scales. Black hole spherical symmetric solutions are also studied omitting the high curvature corrections in the equation of motions. The solutions are regular and the classical singularity is replaced by a “de Sitter-like core” in $r=0$. Black holes may show a “multihorizon” structure depending on the value of the mass. We conclude the paper with a generalization of the Tomboulis theory to a multidimensional spacetime.

We show that the cosmological moduli problem is solved without relying on huge late-time entropy production, if the universal cutoff scale of the theory is a few orders of magnitude smaller than the Planck scale. We obtain a general estimate of the modulus abundance in terms of the inflationary scale and reheating temperature, and find, in particular, that the reheating temperature can be high enough for nonthermal leptogenesis to work.