In nonsupersymmetric grand unified models a “radiative fermion mass hierarchy” can be achieved in which the spectrum of quark and lepton masses is determined entirely by physics at the unification scale, with many relations following from the unified gauge symmetry, and with the masses of the lightest family arising from loops. A simple, realistic, and predictive model of this kind is presented. A “doubly lopsided” structure, known to lead to bilarge neutrino mixing, plays a crucial role in the radiative hierarchy.

Proceeding from the superfield action for $N=4$, $d=1$ nonlinear supermultiplet, equipped with the most general potential term, we find the action describing a charged particle on the sphere $S^3$ in the field of $n$ fixed Dirac dyons. We construct the supercharges and Hamiltonian and analyze some particularly interesting potentials corresponding to the $N=4$ supersymmetric extension of the integrable one- and two-center McIntosh-Cisneros-Zwanziger-Kepler systems on $S^3$.

We explore the addition of fundamental matter to the Klebanov-Witten field theory. We add probe D7-branes to the $\mathcal{N}=1$ theory obtained from placing D3-branes at the tip of the conifold and compute the meson spectrum for the scalar mesons. In the UV limit of massless quarks we find the exact dimensions of the associated operators, which exhibit a simple scaling in the large-charge limit. For the case of massive quarks we compute the spectrum of scalar mesons numerically.

Using recent results from numerical relativity simulations of nonspinning binary black hole mergers, we revisit the problem of detecting ringdown waveforms and of estimating the source parameters, considering both LISA and Earth-based interferometers. We find that Advanced LIGO and EGO could detect intermediate-mass black holes of mass up to $\sim {10}^3{M}_{\odot }$ out to a luminosity distance of a few Gpc. For typical multipolar energy distributions, we show that the single-mode ringdown templates presently used for ringdown searches in the LIGO data stream can produce a significant event loss ($>10\%$ for all detectors in a large interval of black hole masses) and very large parameter estimation errors on the black hole’s mass and spin. We estimate that more than $\sim {10}^6$ templates would be needed for a single-stage multimode search. Therefore, we recommend a “two-stage” search to save on computational costs: single-mode templates can be used for detection, but multimode templates or Prony methods should be used to estimate parameters once a detection has been made. We update estimates of the critical signal-to-noise ratio required to test the hypothesis that two or more modes are present in the signal and to resolve their frequencies, showing that second-generation Earth-based detectors and LISA have the potential to perform no-hair tests.

We develop a parametrized post-Friedmann (PPF) framework which describes three regimes of modified gravity models that accelerate the expansion without dark energy. On large scales, the evolution of scalar metric and density perturbations must be compatible with the expansion history defined by distance measures. On intermediate scales in the linear regime, they form a scalar-tensor theory with a modified Poisson equation. On small scales in dark matter halos such as our own galaxy, modifications must be suppressed in order to satisfy stringent local tests of general relativity. We describe these regimes with three free functions and two parameters: the relationship between the two metric fluctuations, the large and intermediate scale relationships to density fluctuations, and the two scales of the transitions between the regimes. We also clarify the formal equivalence of modified gravity and generalized dark energy. The PPF description of linear fluctuation in $f(R)$ modified action and the Dvali-Gabadadze-Porrati braneworld models show excellent agreement with explicit calculations. Lacking cosmological simulations of these models, our nonlinear halo-model description remains an ansatz but one that enables well-motivated consistency tests of general relativity. The required suppression of modifications within dark matter halos suggests that the linear and weakly nonlinear regimes are better suited for making a complementary test of general relativity than the deeply nonlinear regime.

In the context of a debate on the correct expression of the Hawking temperature of a cosmological black hole, we show that the correct expression in terms of the Hawking-Hayward quasilocal energy $m_H$ of the hole is $T=(8\pi m_H(t){)}^{-1}$. This expression holds for comoving black holes and agrees with a recent proposal by Saida, Harada, and Maeda.

We revisit the issue of the stability in the Dvali-Gabadadze-Porrati model by considering the nucleation of bubbles of the conventional branch within the self-accelerating branch. We construct an instanton describing this process in the thin wall approximation. On one side of the bubble wall, the bulk consists of the exterior of the brane, while on the other side it is the interior. The solution requires the presence of a 2-brane (the bubble wall) which induces the transition. However, we show that this instanton cannot be realized as the thin wall limit of any smooth solution. Once the bubble thickness is resolved, the equations of motion do not allow $O(4)$ symmetric solutions joining the two branches. We conclude that the thin wall instanton is unphysical, and that one cannot have processes connecting the two branches, unless negative tension bubble walls are introduced. This also suggests that the self-accelerating branch does not decay into the conventional branch nucleating bubbles. We comment on other kinds of bubbles that could interpolate between the two branches.

We investigate properties of solutions of the scalar wave equation and Maxwell’s equations on Minkowski space with helical symmetry. Existence of local and global solutions with this symmetry is demonstrated with and without sources. The asymptotic properties of the solutions are analyzed. We show that the Newman-Penrose retarded and advanced scalars exhibit specific symmetries and generalized peeling properties.

We consider the cosmological role of the scalar fields generated by the compactification of 11-dimensional Einstein gravity on a 7-dimensional elliptic twisted torus, which has the attractive features of giving rise to a positive semidefinite potential, and partially fixing the moduli. This compactification is therefore relevant for low-energy $M$-theory, 11-dimensional supergravity. We find that there is no slow-roll inflation within a subclass of these twisted tori and give evidence that this result extends to a more general situation. Despite the lack of slow-roll, we find that there is a novel scaling solution in Friedmann cosmologies in which the massive moduli oscillate but maintain a constant energy density relative to the background barotropic fluid.

We place limits on scalar and vector unparticle couplings to electrons and neutrinos using data from reactor neutrino experiments originally designed to search for neutrino magnetic moment. Upper bounds on standard model lepton-scalar unparticle and lepton-vector unparticle couplings ${\lambda }_0$, and ${\lambda }_1$ are given for various values of the unparticle mass dimension $d$, and the unparticle energy scale ${\Lambda }_{\mathcal{U}}$. Especially for smaller values of the mass dimension $d$ ($1<d<1.3$) these bounds are very significant and comparable to those obtained from production rates at high energy colliders. These bounds are also similar to those obtained by the analysis of the absence of the decay of the low-energy solar and reactor neutrinos.

We discuss the extrema of the two-Higgs-doublet model with different physical properties. We have found necessary and sufficient conditions for realization of the extrema with different properties as the vacuum state of the model. We found explicit equations for extremum energies via parameters of potential if it has explicitly $CP$ conserving form. These equations allow to pick out extremum with lower energy—vacuum state and to look for change of extrema (phase transitions) with the variation of parameters of potential. Our goal is to find a general picture here to apply it for description of the early Universe.

The Higgs sector may play an important role in detecting mirror particles, which can be the candidates of dark matter and appear as missing energy in the detectors at the LHC. In this paper we worked out the Higgs boson spectrum and the Higgs couplings for the symmetric vacuum, namely $v_1=v_2=v$, in the mirror model, and investigated the constraints from electroweak precision observables. Our study showed that electroweak precision observables have already constrained the Higgs boson sector severely. We then explored the Higgs boson phenomenology, and focused on the scenario that the heavier Higgs boson $H$ can decay into a pair of lighter Higgs bosons $h$. We proposed to study the invisible decay of the Higgs boson via the pair production of them, in which one Higgs boson decays into bottom quarks and the other decays invisibly. Our detail simulation for signals and backgrounds showed that the observation of the signal can reach $5\sigma$ significance for $m_H=260\mathrm{GeV}$ and $m_h=115\mathrm{GeV}$ with $10{\mathrm{fb}}^{-1}$ integrated luminosity at the LHC. Moreover the possible method to further suppress dominant $Zb\overline{b}$ background was discussed. We also simulated the signals and backgrounds for $H\to hh\to 4b$. Our results showed that it is very difficult to isolate the signals from huge QCD continuum backgrounds.

We study the lowest-lying scalar mesons in the QCD sum rule by considering them as tetraquark states. We find that there are five independent currents for each state with a certain flavor structure. By forming linear combinations, we find that some mixed currents give reliable QCD sum rules. Among various tetraquark currents, we consider those which are constructed by the diquarks having antisymmetric and symmetric flavor structures. That the results of the QCD sum rule derived from the two types of currents are similar suggests that the tetraquark states can have a large mixing between different flavor structures.

The angular correlation of the electrons emitted in the neutrinoless double beta decay ($0\nu 2\beta$) is presented using a general Lorentz invariant effective Lagrangian for the leptonic and hadronic charged weak currents. We show that the coefficient $K$ in the angular correlation $d\Gamma /d\cos \theta \propto (1-K\cos \theta )$ is essentially independent of the nuclear matrix element models and present its numerical values for the five nuclei of interest (${}^{76}\mathrm{Ge}$, ${}^{82}\mathrm{Se}$, ${}^{100}\mathrm{Mo}$, ${}^{130}\mathrm{Te}$, and ${}^{136}\mathrm{Xe}$), assuming that the $0\nu 2\beta$ decays in these nuclei are induced solely by a light Majorana neutrino, ${\nu }_M$. This coefficient varies between $K=0.81$ (for the ${}^{76}\mathrm{Ge}$ nucleus) and $K=0.88$ (for the ${}^{82}\mathrm{Se}$ and ${}^{100}\mathrm{Mo}$ nuclei), calculated taking into account the effects from the nucleon recoil, the $S$ and $P$ waves for the outgoing electrons and the electron mass. Deviation of $K$ from its values derived here would indicate the presence of new physics (NP) in addition to a light Majorana neutrino, and we work out the angular coefficients in several ${\nu }_M+\mathrm{NP}$ scenarios for the ${}^{76}\mathrm{Ge}$ nucleus. As an illustration of the correlations among the $0\nu 2\beta$ observables (half-life $T_{1/2}$, the coefficient $K$, and the effective Majorana neutrino mass $|⟨m⟩|$) and the parameters of the underlying NP model, we analyze the left-right symmetric models, taking into account current phenomenological bounds on the right-handed $W_R$-boson mass and the left-right mixing parameter $\zeta$.

The decay channels ${\stackrel{(-)}{B}}_d\to {\stackrel{(-)}{D}}^0{\stackrel{(-)}{K}}^{*0}$, ${\stackrel{(-)}{D}}^{*0}{\stackrel{(-)}{K}}^{*0}$ are investigated for extracting weak Cabibbo-Kobayashi-Maskawa (CKM) phase information. These channels are described by color suppressed tree diagrams only and are free from penguin contributions. The branching ratios for these channels are found to be $\sim \mathcal{O}({10}^{-5}–{10}^{-6})$ which can be measured at the currently running $B$ factories. The method presented here may be well suited to determine the CKM angle $\gamma$.

We present a measurement of the top quark pair production cross section in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ utilizing $425{\mathrm{pb}}^{-1}$ of data collected with the D0 detector at the Fermilab Tevatron Collider. We consider the final state of the top quark pair containing one high-$p_T$ electron or muon and at least four jets. We exploit specific kinematic features of $t\overline{t}$ events to extract the cross section. For a top quark mass of 175 GeV, we measure ${\sigma }_{t\overline{t}}={6.4}_{-1.2}^{+1.3}(\mathrm{stat})\pm 0.7(\mathrm{syst})\pm 0.4(\mathrm{lum})\mathrm{pb}$, in good agreement with the standard model prediction.

We study the $e^{+}{e}^{-}\to \mathit{\Lambda }\overline{\mathit{\Lambda }}\gamma$, $\mathit{\Lambda }{\overline{\mathit{\Sigma }}}^0\gamma$, ${\mathit{\Sigma }}^0{\overline{\mathit{\Sigma }}}^0\gamma$ processes using $230{\mathrm{fb}}^{-1}$ of integrated luminosity collected by the BABAR detector at $e^{+}{e}^{-}$ center-of-mass energy of 10.58 GeV. From the analysis of the baryon-antibaryon mass spectra the cross sections for $e^{+}{e}^{-}\to \mathit{\Lambda }\overline{\mathit{\Lambda }}$, $\mathit{\Lambda }{\overline{\mathit{\Sigma }}}^0$, ${\mathit{\Sigma }}^0{\overline{\mathit{\Sigma }}}^0$ are measured in the dibaryon mass range from threshold up to $3\mathrm{GeV}/c^2$. The ratio of electric and magnetic form factors, $|G_E/G_M|$, is measured for $e^{+}{e}^{-}\to \mathit{\Lambda }\overline{\mathit{\Lambda }}$, and limits on the relative phase between $\mathit{\Lambda }$ form factors are obtained. We also measure the $J/\psi \to \mathit{\Lambda }\overline{\mathit{\Lambda }}$, ${\mathit{\Sigma }}^0{\overline{\mathit{\Sigma }}}^0$, and $\psi (2S)\to \mathit{\Lambda }\overline{\mathit{\Lambda }}$ branching fractions.

We present measurements of time-dependent $CP$ asymmetries in $B^0\to \omega K_S^0$, $f_0(980)K_S^0$, $K_S^0{\pi }^0$ and $K^{+}{K}^{-}{K}_S^0$ decays based on a sample of $535\times {10}^6$ $B\overline{B}$ pairs collected at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB energy-asymmetric $e^{+}{e}^{-}$ collider. One neutral $B$ meson is fully reconstructed in one of the specified decay channels, and the flavor of the accompanying $B$ meson is identified from its decay products. $CP$-violation parameters for each of the decay modes are obtained from the asymmetries in the distributions of the proper-time intervals between the two $B$ decays.

We solve for the cosmological perturbations in a five-dimensional background consisting of two separating or colliding boundary branes, as an expansion in the collision speed $V$ divided by the speed of light $c$. Our solution permits a detailed check of the validity of four-dimensional effective theory in the vicinity of the event corresponding to the big crunch/big bang singularity. We show that the four-dimensional description fails at the first nontrivial order in $(V/c{)}^2$. At this order, there is nontrivial mixing of the two relevant four-dimensional perturbation modes (the growing and decaying modes) as the boundary branes move from the narrowly separated limit described by Kaluza-Klein theory to the well-separated limit where gravity is confined to the positive-tension brane. We comment on the cosmological significance of the result and compute other quantities of interest in five-dimensional cosmological scenarios.

If the standard model of particle interactions is extended to include a second scalar doublet $[H^{+},(H^0+i{A}^0)/\sqrt{2}]$, which is odd under an unbroken $Z_2$ discrete symmetry, it may be called the dark scalar doublet, because its lightest neutral member, say $H^0$, is one possible component for the dark matter of the Universe. We discuss the general phenomenology of the four particles of this doublet, without assuming that $H^0$ is the dominant source of dark matter. We also consider the impact of this dark scalar doublet on the phenomenology of the standard-model Higgs boson $h$.