We study the cosmology of a Lee-Wick type scalar field theory. First, we consider homogeneous and isotropic background solutions and find that they are nonsingular, leading to cosmological bounces. Next, we analyze the spectrum of cosmological perturbations which result from this model. Unless either the potential of the Lee-Wick theory or the initial conditions are finely tuned, it is impossible to obtain background solutions which have a sufficiently long period of inflation after the bounce. More interestingly, however, we find that in the generic noninflationary bouncing cosmology, perturbations created from quantum vacuum fluctuations in the contracting phase have the correct form to lead to a scale-invariant spectrum of metric inhomogeneities in the expanding phase. Since the background is nonsingular, the evolution of the fluctuations is defined unambiguously through the bounce. We also analyze the evolution of fluctuations which emerge from thermal initial conditions in the contracting phase. The spectrum of gravitational waves stemming from quantum vacuum fluctuations in the contracting phase is also scale-invariant, and the tensor to scalar ratio is not suppressed.

Mechanisms have been proposed that might rotate the linear polarization of the cosmic microwave background (CMB) as it propagates from the surface of last scatter. In the simplest scenario, the rotation will be uniform across the sky, but the rotation angle may also vary across the sky. We develop in detail the complete set of full-sky quadratic estimators for the rotation of the CMB polarization that can be constructed from the CMB temperature and polarization. We derive the variance with which these estimators can be measured and show that these variances reduce to the simpler flat-sky expressions in the appropriate limit. We evaluate the variances numerically. While the flat-sky formalism may be suitable if the rotation angle arises as a realization of a random field, the full-sky formalism will be required to search for rotations that vary slowly across the sky as well as for models in which the angular power spectrum for the rotation angle peaks at large angles.

The QCD phase structure is studied at finite temperature in a three-flavor random matrix model formulated with nonzero quark chemical potentials. In the case of no flavor mixing, we analytically obtain temperature dependent critical chemical potentials for finite quark masses. Numerical results show that the QCD phase diagram as a function of temperature is qualitatively in agreement with the prediction of the Nambu-Jona-Lasinio model.

We study double Higgs production in photon-photon collisions as a probe of the new dynamics of Higgs interactions in the framework of two Higgs doublet models. We analyze neutral Higgs bosons production and decay in the fusion processes, $\gamma \gamma \to S_i{S}_j$, $S_i=h^0$, $H^0$, $A^0$, and show that both $h^0{h}^0$ and $A^0{A}^0$ production can be enhanced by threshold effects in the region $E_{\gamma \gamma }\approx 2m_{H\pm }$. Resonant effects due to the heavy Higgs $H^0$ can also play a role in the cross section enhancement when it is allowed to decay to two light $CP$-even $h^0$ or to two light $CP$-odd $A^0$ scalars. We have scanned the allowed parameter space of the two Higgs doublet model and found a vast region of the parameter space where the cross section is 2 orders of magnitude above the standard model cross section. We further show that the standard model experimental analysis can be used to discover or to constrain the two Higgs doublet model parameter space.

$CP$ violation from physics beyond the standard model may reside in triple boson vertices of the electroweak theory. We review the effective theory description and discuss how $CP$-violating contributions to these vertices might be discerned by electric dipole moments (EDM) or diboson production at the LHC. Despite triple boson $CP$-violating interactions entering EDMs only at the two-loop level, we find that EDM experiments are generally more powerful than the diboson processes. To give an example to these general considerations we perform the comparison between EDMs and collider observables within supersymmetric theories that have heavy sfermions, such that substantive EDMs at the one-loop level are disallowed. EDMs generally remain more powerful probes, and next-generation EDM experiments may surpass even the most optimistic assumptions for LHC sensitivities.

If the dark matter consists of a weakly interacting massive particle, it can be produced and studied at future collider experiments like those at the LHC. The production of collider-stable weakly interacting massive particles is characterized by hard scattering events with large missing transverse energy. Here we emphasize and discuss the fact that the discovery of events inconsistent with the standard model with large missing transverse energy need not point to the existence of new, collider-stable particles. We explore an alternative explanation where the only sources of missing transverse energy are standard model neutrinos. We present concrete examples of such scenarios, focusing on supersymmetric models with $R$-parity violation. We also discuss means of differentiating neutrino missing energy signals from the production of new collider-stable particles. These include both model-dependent signals, such as particle tags and flavor counts, as well as model-independent tests that attempt to measure the missing particle mass.

The possibility that the gluino is the next to the lightest supersymmetric particle (NLSP) is discussed and it is shown that this situation arises in nonuniversal supergravity models within a significant part of the parameter space compatible with all known experimental bounds. It is then shown that the gluino NLSP (GNLSP) models lead to a compressed sfermion spectrum with the sleptons often heavier than the squarks at least for the first two generations. The relic density here is governed by gluino coannihilation which is responsible for a relatively small mass splitting between the gluino and the neutralino masses. Thus the GNLSP class of models is very predictive first because the supersymmetry (SUSY) production cross sections at the CERN LHC are dominated by gluino production and second because the gluino production itself proceeds dominantly through a single channel which allows for a direct determination of the gluino mass and an indirect determination of the neutralino mass due to a linear relation between these two masses which is highly constrained by coannihilation. A detailed analysis of these models shows that the jet production and tagged $b$ jets from the gluino production can be discriminated from the standard model background with appropriate cuts. It is found that the GNLSP models can be tested with just $10{\mathrm{fb}}^{-1}$ of integrated luminosity and may therefore be checked with low luminosity runs in the first data at the LHC. Thus if a GNLSP model is realized, the LHC will turn into a gluino factory through a profuse production of gluinos with typically only a small fraction $\lesssim 5\%$ of total SUSY events arising from other production modes over the allowed GNLSP model parameter space.

We study $B_d$ and $B_s$ mixing in unquenched lattice QCD employing the MILC Collaboration gauge configurations that include $u$, $d$, and $s$ sea quarks based on the improved staggered quark (AsqTad) action and a highly improved gluon action. We implement the valence light quarks also with the AsqTad action and use the nonrelativistic NRQCD action for the valence $b$ quark. We calculate hadronic matrix elements necessary for extracting Cabibbo-Kobayashi-Maskawa matrix elements from experimental measurements of mass differences $\Delta M_d$ and $\Delta M_s$. We find $\xi \equiv f_{B_s}\sqrt{{\widehat{B}}_{B_s}}/f_{B_d}\sqrt{{\widehat{B}}_{B_d}}=1.258(33)$, $f_{B_d}\sqrt{{\widehat{B}}_{B_d}}=216(15)\mathrm{MeV}$, and $f_{B_s}\sqrt{{\widehat{B}}_{B_s}}=266(18)\mathrm{MeV}$. We also update previous results for decay constants and obtain $f_{B_d}=190(13)\mathrm{MeV}$, $f_{B_s}=231(15)\mathrm{MeV}$, and $f_{B_s}/f_{B_d}=1.226(26)$. The new lattice results lead to updated values for the ratio of Cabibbo-Kobayashi-Maskawa matrix elements $|V_{td}|/|V_{ts}|$ and for the standard model prediction for $\mathrm{Br}(B_s\to {\mu }^{+}{\mu }^{-})$ with reduced errors. We determine $|V_{td}|/|V_{ts}|=0.214(1)(5)$ and $\mathrm{Br}(B_s\to {\mu }^{+}{\mu }^{-})=3.19(19)\times {10}^{-9}$.

We perform a detailed study of the various one-loop contributions leading to production of the standard model Higgs boson in association with a hard jet. This production mode contributes to the current Tevatron exclusion limit of the standard model Higgs with $160\mathrm{GeV}\le M_H\le 170\mathrm{GeV}$, and will also be important for discovery and interpretation of new scalar bosons at the Large Hadron Collider (LHC). We include top- and bottom-quark initiated contributions, maintaining the exact dependence on the quark masses, and also study previously neglected $W$- and $Z$-boson mediated effects which shift the $qg$ and $q\overline{q}$ production modes. We consider the deviations from commonly used approximations for the Higgs boson transverse momentum spectrum caused by the finite top-quark mass, bottom-quark contributions, and electroweak gauge boson terms. All three effects act to decrease the Higgs boson transverse momentum distribution for observable momenta, with shifts reaching $-8\%$ at the Tevatron and $-30\%$ at the LHC. The shifts have a significant dependence on the Higgs $p_T$, and are especially important if large momenta are selected by experimental cuts.

We study the field equations of modified theories of gravity in which the Lagrangian is a general function of the Ricci scalar and Ricci-squared terms in Palatini formalism. We show that the independent connection can be expressed as the Levi-Cività connection of an auxiliary metric which, in particular cases of interest, is related with the physical metric by means of a disformal transformation. This relation between physical and auxiliary metric boils down to a conformal transformation in the case of $f(R)$ theories. We also show with explicit models that the inclusion of Ricci-squared terms in the action can impose upper bounds on the accessible values of pressure and density, which might have important consequences for the early time cosmology and black hole formation scenarios. Our results indicate that the phenomenology of $f(R,R_{\mu \nu }{R}^{\mu \nu })$ theories is much richer than that of $f(R)$ and $f(R_{\mu \nu }{R}^{\mu \nu })$ theories and that they also share some similarities with Bekenstein’s relativistic theory of MOND.

The merger process of a binary black hole system can have a strong impact on a circumbinary disk. In the present work we study the effect of both central mass reduction (due to the energy loss through gravitational waves) and a possible black hole recoil (due to asymmetric emission of gravitational radiation). For the mass reduction case and recoil directed along the disk’s angular momentum, oscillations are induced in the disk which then modulate the internal energy and bremsstrahlung luminosities. On the other hand, when the recoil direction has a component orthogonal to the disk’s angular momentum, the disk’s dynamics are strongly impacted, giving rise to relativistic shocks. The shock heating leaves its signature in our proxies for radiation, the total internal energy and bremsstrahlung luminosity. Interestingly, for cases where the kick velocity is below the smallest orbital velocity in the disk (a likely scenario in real active galactic nuclei), we observe a common, characteristic pattern in the internal energy of the disk. Variations in kick velocity simply provide a phase offset in the characteristic pattern implying that observations of such a signature could yield a measure of the kick velocity through electromagnetic signals alone.

We suppose that a vector field perturbation causes part of the primordial curvature perturbation. The non-Gaussianity parameter $f_{\mathrm{NL}}$ is then, in general, statistically anisotropic. We calculate its form and magnitude in the curvaton scenario and in the end-of-inflation scenario. We show that this anisotropy could easily be observable.

Clusters of galaxies have not yet been detected at gamma-ray frequencies; however, the recently launched Fermi Gamma-ray Space Telescope, formerly known as GLAST, could provide the first detections in the near future. Clusters are expected to emit gamma rays as a result of (1) a population of high-energy cosmic rays fueled by accretion, merger shocks, active galactic nuclei, and supernovae, and (2) particle dark-matter annihilation. In this paper, we ask the question of whether the Fermi telescope will be able to discriminate between the two emission processes. We present data-driven predictions for the gamma-ray emission from cosmic rays and dark matter for a large x-ray-flux-limited sample of galaxy clusters and groups. We point out that the gamma-ray signals from cosmic rays and dark matter can be comparable. In particular, we find that poor clusters and groups are the systems predicted to have the highest dark-matter to cosmic-ray emission ratio at gamma-ray energies. Based on detailed Fermi simulations, we study observational handles that might enable us to distinguish the two emission mechanisms, including the gamma-ray spectra, the spatial distribution of the signal, and the associated multiwavelength emissions. We also propose optimal hardness ratios, which will help us to understand the nature of the gamma-ray emission. Our study indicates that gamma rays from dark-matter annihilation with a high particle mass can be distinguished from a cosmic-ray spectrum even for fairly faint sources. Discriminating a cosmic-ray spectrum from a light dark-matter particle will be, instead, much more difficult, and will require long observations and/or a bright source. While the gamma-ray emission from our simulated clusters is extended, determining the spatial distribution with Fermi will be a challenging task requiring an optimal control of the backgrounds.

The relativistic four-quark equations are found in the framework of the dispersion relation technique. The dynamical mixing of the four-quark amplitudes and the glueball amplitudes is considered. The approximate solutions of these equations using the method based on the extraction of leading singularities of the amplitudes are obtained. The four-quark amplitudes of exotic mesons including the quarks of three flavors $(u,d,s)$ are calculated. The poles of these amplitudes determine the masses of the exotic mesons.

Both the mass (just below the $D^{*0}{\overline{D}}^0$ threshold) and the likely quantum numbers ($J^{PC}=1^{++}$) of the $X(3872)$ suggest that it is either a weakly bound hadronic “molecule” ($X(3872)\sim 1/\sqrt{2}[D^{*0}{\overline{D}}^0+{\overline{D}}^{*0}{D}^0]$) or a virtual state of charmed mesons. Assuming the $X(3872)$ is a weakly bound molecule, the scattering of neutral $D$ and $D^{*}$ mesons off the $X(3872)$ can be predicted from the $X(3872)$ binding energy. We calculate the phase shifts and cross section for scattering of $D^0$ and $D^{*0}$ mesons and their antiparticles off the $X(3872)$ in an effective field theory for short-range interactions. This provides another example of a three-body process, along with those in nuclear and atomic systems, that displays universal properties. It may be possible to extract the scattering within the final state interactions of $B_c$ decays and/or other LHC events.

We show that at certain values of QCD condensates the nucleon QCD sum rules with the “$\mathrm{\text{pole}}+\mathrm{\text{continuum}}$” model for the hadron spectrum obtain an unphysical solution. This provides constraints for the values of condensates to be consistent with the existence of a physical solution. The constraints become much weaker if the radiative corrections are included perturbatively. We demonstrate that the most important dependence of nucleon mass on the quark scalar condensate becomes less pronounced under a factorization assumption for the four-quark and six-quark condensates.

We present a search for standard model Higgs boson production in association with a $W$ boson in proton-antiproton collisions ($p\overline{p}\to W^{\pm }H\to \ell \nu b\overline{b}$) at a center of mass energy of 1.96 TeV. The search employs data collected with the CDF II detector that correspond to an integrated luminosity of approximately $1.9{\mathrm{fb}}^{-1}$. We select events consistent with a signature of a single charged lepton ($e^{\pm }/{\mu }^{\pm }$), missing transverse energy, and two jets. Jets corresponding to bottom quarks are identified with a secondary vertex tagging method, a jet probability tagging method, and a neural network filter. We use kinematic information in an artificial neural network to improve discrimination between signal and background compared to previous analyses. The observed number of events and the neural network output distributions are consistent with the standard model background expectations, and we set 95% confidence level upper limits on the production cross section times branching fraction ranging from 1.2 to 1.1 pb or 7.5 to 102 times the standard model expectation for Higgs boson masses from 110 to $150\mathrm{GeV}/c^2$, respectively.

In this work, we employ the techniques used to cure the indefinite norm problem in pseudo-Hermitian Hamiltonians to show that the ghost states in a higher derivative scalar field theory are not real ghosts. For the model under investigation, an imaginary auxiliary field is introduced to have an equivalent non-Hermitian two-field scalar theory. We were able to calculate exactly the positive definite metric operator $\eta$ for the quantum mechanical as well as the quantum field versions of the theory. While the equivalent Hamiltonian is non-Hermitian in a Hilbert space characterized by the Dirac sense inner product, it is, however, a Hermitian in a Hilbert space endowed with the inner product $⟨n|\eta |m⟩$. The main feature of the latter Hilbert space is that the propagator has the correct sign (no Lee-Wick fields). Moreover, the calculated metric operator diagonalizes the Hamiltonian in the two fields (no mixing). We found that the Hermiticity of the calculated metric operator to lead to the constrain $M>2m$ for the two Higgs masses, in agreement with other calculations in the literature. Besides, our mass formulas coincide with those obtained in other works (obtained by a very different regime but with the existence of ghost states), which means that our positive normed Hamiltonian form preserves the mass spectra.

We determine finite temperature corrections to the heavy-quark (static) potential as a function of the shear viscosity-to-entropy density ratio in a strongly coupled, large-$N_c$ conformal field theory dual to five-dimensional Gauss-Bonnet gravity. We find that these corrections are even smaller than those predicted by perturbative QCD at distances relevant for small bound states in a deconfined plasma. Obtaining the dominant temperature and viscosity dependence of quarkonium binding energies will require a theory where conformal invariance is broken in such a way that the free energy associated with a single heavy quark is not just a pure entropy contribution.