It was recently realized that matter modeled by the scalar field sector of the Lee-Wick standard model yields, in the context of a homogeneous and isotropic cosmological background, a bouncing cosmology. However, bouncing cosmologies induced by pressureless matter are in general unstable to the addition of relativistic matter (i.e. radiation). Here we study the possibility of obtaining a bouncing cosmology if we add not only radiation, but also its Lee-Wick partner, to the matter sector. We find that, in general, no bounce occurs. The only way to obtain a bounce is to choose initial conditions with very special phases of the radiation field and its Lee-Wick partner.

Even if new physics beyond the standard model indeed exists, the energy scale of new physics might be beyond the reach at the Large Hadron Collider (LHC), and the LHC could find only the Higgs boson but nothing else. This is the so-called “nightmare scenario.” On the other hand, the existence of the dark matter has been established from various observations. One of the promising candidates for thermal relic dark matter is a stable and electric charge-neutral weakly interacting massive particle (WIMP) with mass below the TeV scale. In the nightmare scenario, we introduce a WIMP dark matter singlet under the standard model gauge group, which only couples to the Higgs doublet at the lowest order, and investigate the possibility that such WIMP dark matter can be a clue to overcome the nightmare scenario via various phenomenological tests such as the dark matter relic abundance, the direct detection experiments for the dark matter particle, and the production of the dark matter particle at the LHC.

We use gauge/gravity duality to study the thermodynamics of a generic almost conformal theory, specified by its beta function. Three different phases are identified, a high temperature phase of massless partons, an intermediate quasiconformal phase and a low temperature confining phase. The limit of a theory with infrared fixed point, in which the coupling does not run to infinity, is also studied. The transitions between the phases are of first order or continuous, depending on the parameters of the beta function. The results presented follow from gauge/gravity duality; no specific boundary theory is assumed, only its beta function.

We introduce a new class of infrared safe jet observables, which we refer to as template overlaps, designed to filter targeted highly-boosted particle decays from QCD jets and other background. Template overlaps are functional measures that quantify how well the energy flow of a physical jet matches the flow of a boosted partonic decay. Any region of the partonic phase space for the boosted decays defines a template. We will refer to the maximum functional overlap found this way as the template overlap. To illustrate the method, we test lowest-order templates designed to distinguish highly-boosted top and Higgs decays from backgrounds produced by event generators. For the functional overlap, we find good results with a simple construction based on a Gaussian in energy differences within angular regions surrounding the template partons. Although different event generators give different averages for our template overlaps, we find in each case excellent rejection power, especially when combined with cuts based on jet shapes. The template overlaps are capable of systematic improvement by including higher-order corrections in the template phase space.

We analyze the general structure of four-fermion operators capable of introducing $CP$ violation preferentially in $B_s$ mixing within the framework of minimal flavor violation. The effect requires a minimum of $O(Y_u^4{Y}_d^4)$ Yukawa insertions, and at this order we find a total of six operators with different Lorentz, color, and flavor contractions that lead to enhanced $B_s$ mixing. We then estimate the impact of these operators and of their close relatives on the possible sizes of electric dipole moments (EDMs) of neutrons and heavy atoms. We identify two broad classes of such operators: those that give EDMs in the limit of vanishing Cabibbo-Kobayashi-Maskawa angles, and those that require quark mixing for the existence of nonzero EDMs. The natural value for EDMs from the operators in the first category is up to an order of magnitude above the experimental upper bounds, while the second group predicts EDMs well below the current sensitivity level. Finally, we discuss plausible UV completions for each type of operator.

We make use of a self-consistent quark-model based study of four-quark charmonium-like states to interpret recent charmonium experimental data. We conclude that there exists a $D^{*}{\overline{D}}^{*}$ meson-meson molecule with quantum numbers $(I^G)J^{PC}=(1^{-})2^{++}$. Our study confirms the presence of charged charmonium-like resonances on the excited charmonium spectrum. We find support from recent experimental data by the Belle Collaboration [R. Mizuk et al. (Belle Collaboration), Phys. Rev. D 78, 072004 (2008)]. Confirmation of the experimental data by the Belle Collaboration and the determination of the quantum numbers of the new structures would help in discriminating among different theoretical models and would give further support to the theoretical analysis of T. Fernández-Caramés, A. Valcarce, and J. Vijande [Phys. Rev. Lett. 103, 222001 (2009)].

We study lepton number violating decays of charged $K$, $D$, $D_s$, $B$, and $B_c$ mesons of the form $M^{+}\to M^{\prime -}{\ell }^{+}{\ell }^{+}$, induced by the existence of Majorana neutrinos. These processes provide information complementary to neutrinoless double nuclear beta decays, and are sensitive to neutrino masses and lepton mixing. We explore neutrino mass ranges $m_N$ from below 1 eV to several hundred GeV. We find that in many cases the branching ratios are prohibitively small, however in the intermediate range $m_{\pi }<m_N<m_{B_c}$, in specific channels and for specific neutrino masses, the branching ratios can be at the reach of high luminosity experiments like those at the LHC-$b$ and future super flavor factories, and can provide bounds on the lepton mixing parameters.

The positron anomaly recently reported by the cosmic-ray measurements suggests that, if explained by the decay of dark matter particle, the decay source is closely linked with the leptonic sector of the standard model. It is observed that, with a simple dimensional analysis, the lifetime of dark matter for the anomaly is expressed by the energy scale of neutrino masses. We present two scenarios in which these two matters at issue (the dark matter width and the tiny neutrino masses) stem from a single operator involving a gauge-singlet scalar field.

The scale invariant of the effective potential of the standard model at two loop is used as a boundary condition under the assumption that the two-loop effective potential approximates the full effective potential. This condition leads with the help of the renormalization-group functions of the model at two loop to an algebraic equation of the scalar self-coupling with coefficients that depend on the gauge and the top quark couplings. It admits only two real positive solutions. One of them, in the absence of the gauge and top quark couplings, corresponds to the nonperturbative ultraviolet fixed point of the scalar renormalization-group function and the other corresponds to the perturbative infrared fixed point. The dependence of the scalar coupling on the top quark and the strong couplings at two-loop radiative corrections is analyzed.

We present results of a search for anomalous production of two photons together with an electron, muon, $\tau$ lepton, missing transverse energy, or jets using $p\overline{p}$ collision data from $1.1–2.0{\mathrm{fb}}^{-1}$ of integrated luminosity collected by the Collider Detector at Fermilab (CDF). The event yields and kinematic distributions are examined for signs of new physics without favoring a specific model of new physics. The results are consistent with the standard model expectations. The search employs several new analysis techniques that significantly reduce instrumental backgrounds in channels with an electron and missing transverse energy.

We perform a study of exclusive production of $D_s^{+}{D}_s^{-}$, $D_s^{*+}{D}_s^{-}$, and $D_s^{*+}{D}_s^{*-}$ final states in initial-state-radiation events from $e^{+}{e}^{-}$ annihilations at a center-of-mass energy near 10.58 GeV, to search for charmonium $1^{--}$ states. The data sample corresponds to an integrated luminosity of $525{\mathrm{fb}}^{-1}$ and was recorded by the BABAR experiment at the PEP-II storage ring. The $D_s^{+}{D}_s^{-}$, $D_s^{*+}{D}_s^{-}$, and $D_s^{*+}{D}_s^{*-}$ mass spectra show evidence of the known $\psi$ resonances. Limits are extracted for the branching ratios of the decays $X(4260)\to D_s^{(*)+}{D}_s^{(*)-}$.

We construct a cosmological toy model based on a Finslerian structure of space-time. In particular, we are interested in a specific Finslerian Lorentz violating theory based on a curved version of Cohen and Glashow’s very special relativity. The osculation of a Finslerian manifold to a Riemannian manifold leads to the limit of relativistic cosmology, for a specified observer. A modified flat Friedmann-Robertson-Walker cosmology is produced. The analogue of a zero energy particle unfolds some special properties of the dynamics. The kinematical equations of motion are affected by local anisotropies. Seeds of Lorentz violations may trigger density inhomogeneities to the cosmological fluid.

Employing higher-order perturbation theory, we find a new class of charged rotating black hole solutions of Einstein-Maxwell-dilaton theory with general dilaton coupling constant. Starting from the Myers-Perry solutions, we use the electric charge as the perturbative parameter, and focus on extremal black holes with equal-magnitude angular momenta in odd dimensions. We perform the perturbations up to 4th order for black holes in 5 dimensions and up to 3rd order in higher odd dimensions. We calculate the physical properties of these black holes and study their dependence on the charge and the dilaton coupling constant.

We study the structure of neutron stars in $f(R)$ gravity theories with perturbative constraints. We derive the modified Tolman-Oppenheimer-Volkov equations and solve them for a polytropic equation of state. We investigate the resulting modifications to the masses and radii of neutron stars and show that observations of surface phenomena alone cannot break the degeneracy between altering the theory of gravity versus choosing a different equation of state of neutron-star matter. On the other hand, observations of neutron-star cooling, which depends on the density of matter at the stellar interior, can place significant constraints on the parameters of the theory.

Because of their strong gravitational field, neutron stars capture weakly interacting dark matter particles (WIMPs) more efficiently compared to other stars, including the white dwarfs. Once captured, the WIMPs sink to the neutron star center and annihilate, heating the star. We find that this heat could lead to detectable effects on the surface temperature of old neutron stars, especially those in dark-matter-rich regions such as the Galactic center or cores of globular clusters. The capture and annihilation is fully efficient even for WIMP-to-nucleon cross sections (elastic or inelastic) as low as $\sim {10}^{-45}{\mathrm{cm}}^2$, and for the annihilation cross sections as small as $\sim {10}^{-57}{\mathrm{cm}}^2$. Thus, detection of a sufficiently cold neutron star in a dark-matter-rich environment would exclude a wide range of dark matter candidates, including those with extremely small cross sections.

Our universe may have formed via bubble nucleation in an eternally inflating background. Furthermore, the background may have a compact dimension—the modulus of which tunnels out of a metastable minimum during bubble nucleation—which subsequently grows to become one of our three large spatial dimensions. When in this scenario our bubble universe collides with other ones like it, the collision geometry is constrained by the reduced symmetry of the tunneling instanton. While the regions affected by such bubble collisions still appear (to leading order) as disks in an observer’s sky, the centers of these disks all lie on a single great circle, providing a distinct signature of anisotropic bubble nucleation.

A generic prediction in the paradigm of weakly interacting dark matter is the production of relativistic particles from dark matter pair annihilation in regions of high dark matter density. Ultrarelativistic electrons and positrons produced in the center of the Galaxy by dark matter annihilation should produce a diffuse synchrotron emission. While the spectral shape of the synchrotron dark matter haze depends on the particle model (and secondarily on the Galactic magnetic fields), the morphology of the haze depends primarily on (1) the dark matter density distribution, (2) the Galactic magnetic field morphology, and (3) the diffusion model for high-energy cosmic-ray leptons. Interestingly, an unidentified excess of microwave radiation with characteristics similar to those predicted by dark matter models has been claimed to exist near the Galactic center region in the data reported by the Wilkinson Microwave Anisotropy Probe (WMAP) satellite, and is dubbed the “WMAP haze.” In this study, we carry out a self-consistent treatment of the variables enumerated above, enforcing constraints from the available data on cosmic rays, radio surveys, and diffuse gamma rays. We outline and make predictions for the general morphology and spectral features of a “dark matter haze” and we compare them to the WMAP haze data. We also characterize and study the spectrum and spatial distribution of the inverse-Compton emission resulting from the same population of energetic electrons and positrons. We point out that the spectrum and morphology of the radio emission at different frequencies are powerful diagnostics to test whether a Galactic synchrotron haze indeed originates from dark matter annihilation.

We investigate the dynamics of homogeneous phase space for single-field models of inflation. Inflationary trajectories are formally attractors in phase space, but since in practice not all initial conditions lead to them, some degree of fine-tuning is required for successful inflation. We explore how the dynamics of noncanonical inflation, which is driven by the potential energy but has additional kinetic terms that are powers of the kinetic energy, can play a role in ameliorating the initial-conditions fine-tuning problem. We present an analysis of inflationary phase space based on the dynamical behavior of the scalar field. This allows us to construct the flow of trajectories, finding that they generically decay towards the inflationary solution at a steeper angle for noncanonical kinetic terms, in comparison to canonical kinetic terms, so that a larger fraction of the initial-conditions space leads to inflation. Thus, noncanonical kinetic terms can be important for removing the initial conditions fine-tuning problem of some small-field inflation models.

We study the consequences of the large dimuon asymmetry observed at D0. Physics beyond the standard model (SM) in $B_s-{\overline{B}}_s$ mixing is required to explain the data. We first present a detailed analysis for model independent constraints on physics beyond the SM, and then study the implications for theoretical models which modify the SM results in different ways, such as $Z^{\prime }$ with flavor changing neutral current and $R$-parity violating supersymmetry contributions.