We revisit the stability and triviality bounds on the Higgs boson mass in the context of the standard model with three and four generations (SM3 and SM4, respectively). In light of the recent results from LHC, the triviality bound in the SM3 has now become obsolete, and the stability bound implies for a Higgs mass of e.g. $m_H=115\mathrm{GeV}$ the onset of new physics before $\Lambda =650\mathrm{TeV}$, whereas there are no limits for $m_H\ge 133\mathrm{GeV}$. For the SM4, the stability and triviality curves intersect and bound a finite region. As a consequence, the fourth generation fermions place stringent theoretical limits on the Higgs mass, and there is a maximal scale beyond which the theory cannot be perturbatively valid. We find that the Higgs mass cannot exceed 700 GeV for any values of the fourth generation fermion masses. Turning the argument around, the absence of a Higgs signal for $m_H\le 600\mathrm{GeV}$ excludes a fourth generation with quark masses below 300 GeV and lepton masses below 350 GeV. In particular, the quark bounds also hold for the small mixing scenarios for which the direct limits from Tevatron and LHC are not applicable, and the lepton bounds we obtain are stronger than the collider limits. If a Higgs boson lighter than 700 GeV is not observed, a fourth generation of chiral fermions with perturbative Yukawa couplings will be conclusively excluded for the full range of parameters.

We examine the possibility that the $SU(2{)}_L$ gauge group of the standard model appears as the dual “magnetic” gauge group of a supersymmetric gauge theory; thus the $W$ and $Z$ (and through mixing, the photon) are composite (or partially composite) gauge bosons. Fully composite gauge bosons are expected to interact strongly at the duality scale, and a large running is needed to match the electroweak gauge couplings. Alternatively one can mix the composite magnetic gauge bosons with some elementary ones to obtain realistic models. In the simplest and most compelling example the Higgs and top are composite, the $W$ and $Z$ partially composite, and the light fermions elementary. The effective theory is a next-to-MSSM-type model where the singlet is a component of the composite meson. There is no little hierarchy problem and the Higgs mass can be as large as 400 GeV. This “fat Higgs”-like model can be considered as an explicit four-dimensional implementation of Randall-Sundrum-type models with gauge fields in the bulk.

We present results for the mixing of quark flavor eigenstates to form low-lying vector and tensor meson mass eigenstates in a generalized QCD-like theory with $\ell$ massless or light, degenerate quarks and one quark of substantial mass, $m_Q$. We show that as $m_Q/\Lambda$ gets large, where $\Lambda$ is the confinement scale, the angle governing this mixing approaches $\arctan (1/\sqrt{\ell })$. We give a generalization of the Gell-Mann Okubo mass relation for this theory. A comparison of the $\ell =2$ results with data on $\omega$-$\varphi$ and $f_2(1275)$-$f_2^{\prime }(1525)$ mixing is included.

We present a simple, perturbative, and renormalizable model with a flavor symmetry which can explain both the $t\overline{t}$ forward-backward asymmetry and the bump feature present in the dijet mass distribution of the $W+jj$ sample in the range 120–160 GeV that was recently reported by the CDF collaboration. The flavor symmetry not only ensures the flavor/$CP$ safety of the model, but also relates the two anomalies unambiguously. It predicts a comparable forward-backward asymmetry in $c\overline{c}$. The forward-backward asymmetry in $b\overline{b}$ is, however, small. A bump in the dijet mass distribution in $Z+jj$ sample is also predicted but with a suppressed cross section.

We show that the lightest pseudotensor mesons $J^{\mathrm{PC}}=2^{-+}$ can be regarded as molecules made of a pseudoscalar $(P)$ $0^{-+}$ and a tensor $2^{++}$ meson, where the latter is itself made of two vector ($V$) mesons. The idea stems from the fact that the vector-vector interaction in $s$ wave and spin 2 is very strong, to the point of generating the $2^{++}$ tensor mesons. On the other hand the interaction of a pseudoscalar with a vector meson in $s$ wave is also very strong and it generates dynamically the lightest axial-vector mesons. Therefore we expect the $PVV$ interaction to be strongly attractive and thus able to build up quasibound $PVV$ resonances. We calculate the three-body $PVV$ interaction by using the fixed center approximation to the Faddeev equations where the two vectors are clustered forming a tensor meson. We find clear resonant structures which can be identified with the ${\pi }_2(1670)$, ${\eta }_2(1645)$ and $K_2^{*}(1770)$ ($2^{-+}$) pseudotensor mesons.

We study the $\mathit{{\rm Y}}(3S,2S)\to \eta \mathit{{\rm Y}}(1S)$ and $\mathit{{\rm Y}}(3S,2S)\to {\pi }^{+}{\pi }^{-}\mathit{{\rm Y}}(1S)$ transitions with $122\times {10}^6\mathit{{\rm Y}}(3S)$ and $100\times {10}^6\mathit{{\rm Y}}(2S)$ mesons collected by the BABAR detector at the PEP-II asymmetric-energy $e^{+}{e}^{-}$ collider. We measure $\mathcal{B}[\mathit{{\rm Y}}(2S)\to \eta \mathit{{\rm Y}}(1S)]=(2.39\pm 0.31(\mathrm{stat}.)\pm 0.14(\mathrm{syst}.))\times {10}^{-4}$ and $\Gamma [\mathit{{\rm Y}}(2S)\to \eta \mathit{{\rm Y}}(1S)]/\Gamma [\mathit{{\rm Y}}(2S)\to {\pi }^{+}{\pi }^{-}\mathit{{\rm Y}}(1S)]=(1.35\pm 0.17(\mathrm{stat}.)\pm 0.08(\mathrm{syst}.))\times {10}^{-3}$. We find no evidence for $\mathit{{\rm Y}}(3S)\to \eta \mathit{{\rm Y}}(1S)$ and obtain $\mathcal{B}[\mathit{{\rm Y}}(3S)\to \eta \mathit{{\rm Y}}(1S)]<1.0\times {10}^{-4}$ and $\Gamma [\mathit{{\rm Y}}(3S)\to \eta \mathit{{\rm Y}}(1S)]/\Gamma [\mathit{{\rm Y}}(3S)\to {\pi }^{+}{\pi }^{-}\mathit{{\rm Y}}(1S)]<2.3\times {10}^{-3}$ as upper limits at the 90% confidence level. We also provide improved measurements of the $\mathit{{\rm Y}}(2S)-\mathit{{\rm Y}}(1S)$ and $\mathit{{\rm Y}}(3S)-\mathit{{\rm Y}}(1S)$ mass differences, $562.170\pm 0.007(\mathrm{stat}.)\pm 0.088(\mathrm{syst}.)\mathrm{MeV}/c^2$ and $893.813\pm 0.015(\mathrm{stat}.)\pm 0.107(\mathrm{syst}.)\mathrm{MeV}/c^2$, respectively.

At $\sqrt{s}=57\pm 7$ TeV, the Pierre Auger Observatory (PAO) measured the $p$-air inelastic production cross section, ${\sigma }_{p-\mathrm{air}}^{\mathrm{prod}}=475\pm 22(\mathrm{stat}){\pm }_{15}^{20}(\mathrm{syst})$ mb, assuming a proton cosmic ray beam with a 25% helium contamination. From a Glauber calculation, they found the inelastic $pp$ cross section, ${\sigma }_{\mathrm{inel}}=90\pm 7(\mathrm{stat}){\pm }_{11}^9(\mathrm{syst})\pm 1.5(\mathrm{Glaub})$ mb. Our parameterization of $\overline{p}p$ and $pp$ total cross sections, ${\sigma }_{\mathrm{tot}}$, using analyticity constraints and unitarity gives accurate extrapolations to ultrahigh energies, and after using a Glauber calculation, accurate predictions for ${\sigma }_{p-\mathrm{air}}^{\mathrm{prod}}$. We find (i) a $pp$ total cross section, ${\sigma }_{\mathrm{tot}}=133.4\pm 1.6$ mb and (ii) ${\sigma }_{p-\mathrm{air}}^{\mathrm{prod}}=483\pm 3$ mb, independently determining a 19% helium contamination. Using our 57 TeV value for $pp$ ${\sigma }_{\mathrm{tot}}$ [M. M. Block and F. Halzen, arXiv:1109-2041], we find a $pp$ inelastic cross section, ${\sigma }_{\mathrm{inel}}=92.9\pm 1.6$ mb, agreeing with POA.

Using a sample of $122\times {10}^6$ ${\rm Y}(3S)$ events recorded with the BABAR detector at the PEP-II asymmetric-energy $e^{+}{e}^{-}$ collider at SLAC, we search for the $h_b(1P)$ spin-singlet partner of the $P$-wave ${\chi }_{bJ}(1P)$ states in the sequential decay ${\rm Y}(3S)\to {\pi }^0{h}_b(1P)$, $h_b(1P)\to \gamma {\eta }_b(1S)$. We observe an excess of events above background in the distribution of the recoil mass against the ${\pi }^0$ at mass $9902\pm 4(\mathrm{stat})\pm 2(\mathrm{syst})\mathrm{MeV}/c^2$. The width of the observed signal is consistent with experimental resolution, and its significance is $3.1\sigma$, including systematic uncertainties. We obtain the value $(4.3\pm 1.1(\mathrm{stat})\pm 0.9(\mathrm{syst}))\times {10}^{-4}$ for the product branching fraction $\mathcal{B}({\rm Y}(3S)\to {\pi }^0{h}_b)\times \mathcal{B}(h_b\to \gamma {\eta }_b)$.

Many theoretical attempts toward reconstructing the potential and dynamics of the scalar fields have been done in the literature by establishing a connection between holographic/agegraphic energy density and a scalar-field model of dark energy. However, in most of these cases the analytical form of the potentials in terms of the scalar field have not been reconstructed due to the complexity of the equations involved. In this paper, by taking Hubble radius as system’s IR cutoff, we are able to reconstruct the analytical form of the potentials as a function of scalar field, namely, $V=V(\varphi )$ as well as the dynamics of the scalar fields as a function of time, namely, $\varphi =\varphi (t)$, by establishing the correspondence between holographic energy density and quintessence, tachyon, $K$-essence, and dilaton energy density in a flat Friedmann-Robertson-Walker universe.

We construct heterotic standard models by compactifying on smooth Calabi-Yau three-folds in the presence of purely Abelian internal gauge fields. A systematic search over complete intersection Calabi-Yau manifolds with less than six Kähler parameters leads to over 200 such models which we present. Each of these models has precisely the matter spectrum of the minimal supersymmetric standard model, at least one pair of Higgs doublets, the standard model gauge group, and no exotics. For about 100 of these models there are four additional $U(1)$ symmetries which are Green-Schwarz anomalous and, hence, massive. In the remaining cases, three $U(1)$ symmetries are anomalous, while the fourth, massless one can be spontaneously broken by singlet vacuum expectation values. The presence of additional global $U(1)$ symmetries, together with the possibility of switching on singlet vacuum expectation values, leads to a rich phenomenology which is illustrated for a particular example. Our database of standard models, which can be further enlarged by simply extending the computer-based search, allows for a detailed and systematic phenomenological analysis of string standard models, covering issues such as the structure of Yukawa couplings, $R$-parity violation, proton stability, and neutrino masses.

Recent results of the Pierre Auger (Auger) fluorescence detectors indicate an increasingly heavy composition of ultra-high energy (UHE) cosmic rays (CRs). Assuming that this trend continues up to the highest energies observed by the Auger surface detectors, we derive the constraints this places on the local source distribution of UHE CR nuclei. Utilizing an analytic description of UHE CR propagation, we derive the expected spectra and composition for a wide range of source emission spectra. We find that sources of intermediate-to-heavy nuclei are consistent with the observed spectra and composition data above the ankle. This consistency requires the presence of nearby sources within 60 Mpc and 80 Mpc for silicon and iron-only sources, respectively. The necessity of these local sources becomes even more compelling in the presence nano-Gauss local extragalactic magnetic fields.

The strong tidal forces that arise during the last stages of the life of a black hole-neutron star binary may severely distort, and possibly disrupt, the star. Both phenomena will imprint signatures about the stellar structure in the emitted gravitational radiation. The information from the disruption, however, is confined to very high frequencies, where detectors are not very sensitive. We thus assess whether the lack of tidal distortion corrections in data-analysis pipelines will affect the detection of the inspiral part of the signal and whether these may yield information on the equation of state of matter at nuclear densities. Using recent post-Newtonian expressions and realistic equations of state to model these scenarios, we find that point-particle templates are sufficient for the detection of black hole-neutron star inspiralling binaries, with a loss of signals below 1% for both second- and third-generation detectors. Such detections may be able to constrain particularly stiff equations of state, but will be unable to reveal the presence of a neutron star with a soft equation of state.

The gravitational interactions of the four-dimensional effective theory describing a general $N$-brane model in five dimensions without radion stabilization are analyzed. Both uncompactified and orbifolded models are considered. The parameter space is constrained by requiring that there be no ghost modes in the theory, and that the Eddington parametrized post-Newtonian parameter $\gamma$ be consistent with observations. We show that we must reside on the brane on which the warp factor is maximized. The resultant theory contains $N-1$ radion modes in a nonlinear sigma model, with the target space being a subset of hyperbolic space. Imposing observational constraints on the relative strengths of gravitational interactions of dark and visible matter shows that at least 99.8% of the dark matter must live on our brane in this model.

An analytic understanding of the geodesic structure around non-Kerr spacetimes will result in a powerful tool that could make the mapping of spacetime around massive quiescent compact objects possible. To this end, I present an analytic closed form expression for the components of a the fourth order Killing tensor for stationary axisymmetric vacuum (SAV) spacetimes. It is as yet unclear what subset of SAV spacetimes admit this solution. The solution is written in terms of an integral expression involving the metric functions and two specific Green’s functions. A second integral expression has to vanish in order for the solution to be exact. In the event that the second integral does not vanish it is likely that the best fourth order approximation to the invariant has been found. This solution can be viewed as a generalized Carter constant providing an explicit expression for the fourth invariant, in addition to the energy, azimuthal angular momentum and rest mass, associated with geodesic motion in SAV spacetimes, be it exact or approximate. I further comment on the application of this result for the founding of a general algorithm for mapping the spacetime around compact objects using gravitational wave observatories.

We explore the effects of heavy degrees of freedom on the evolution and perturbations of light modes in multifield inflation. We use a simple two-field model as an example to illustrate the subtleties of integrating out massive fields in a time-dependent background. We show that when adiabaticity is violated due to a sharp turn in field space, the roles of massive and massless field are interchanged, and furthermore the fields are strongly coupled; thus the system cannot be described by an effective single-field action. Further analysis shows that the sharp turn imparts a non-Bunch-Davis component in each perturbation mode, leading to oscillatory features in the power spectrum, and a large resonantly enhanced bispectrum.

We exploit the spin and kinematic correlations in the decay of a scalar boson into a pair of real or virtual $W$-bosons, with both $W$-bosons decaying leptonically, for Higgs boson discovery at 7 TeV LHC energy with $10{\mathrm{fb}}^{-1}$ luminosity. Without reconstruction of the events, we obtain estimators of the Higgs mass from the peak and width of the signal distribution in $m_{ll}$. The separation of signal and background with other distributions, such as the azimuthal angle between two $W$ decay planes, the rapidity difference between the two leptons, missing $E_T$, and the $p_T$ of leptons, are also prescribed. Our approach identifies the salient Higgs to dilepton signatures that allow subtraction of the continuum $W*W*$ background.

We study the hydrostatic equilibrium configuration of an admixture of degenerate dark matter and normal nuclear matter by using a general relativistic two-fluid formalism. We consider non-self-annihilating dark matter particles of mass $\sim 1\mathrm{GeV}$. The mass-radius relations and moments of inertia of these dark-matter admixed neutron stars are investigated and the stability of these stars is demonstrated by performing a radial perturbation analysis. We find a new class of compact stars which consists of a small normal matter core with radius of a few kilometers embedded in a ten-kilometer-sized dark matter halo. These stellar objects may be observed as extraordinarily small neutron stars that are incompatible with realistic nuclear matter models.

Motivated by recent studies of deep inelastic scattering off the $\mathcal{N}=4$ super-Yang-Mills (SYM) plasma, holographically dual to an ${\mathrm{AdS}}_5\times S^5$ black hole, we use the spacelike flavor current to probe the internal structure of one holographic quark-gluon plasma, which is described by the Sakai-Sugimoto model at high temperature phase (i.e., the chiral-symmetric phase). The plasma structure function is extracted from the retarded flavor current-current correlator. Our main aim in this paper is to explore the effect of nonconformality on these physical quantities. As usual, our study is under the supergravity approximation and the limit of large color number. Although the Sakai-Sugimoto model is nonconformal, which makes the calculations more involved than the well-studied $\mathcal{N}=4$ SYM case, the result seems to indicate that the nonconformality has little essential effect on the physical picture of the internal structure of holographic plasma, which is consistent with the intuition from the asymptotic freedom of QCD at high energy. While the physical picture underlying our investigation is same as the deep inelastic scattering off the $\mathcal{N}=4$ SYM plasma with(out) flavor, the plasma structure functions are quantitatively different, especially their scaling dependence on the temperature, which can be recognized as model dependent. As a comparison, we also do the same analysis for the noncritical version of the Sakai-Sugimoto model which is conformal in the sense that it has a constant dilaton vacuum. The result for this noncritical model is quite similar to the conformal $\mathcal{N}=4$ SYM plasma. We therefore attribute the above difference to the effect of nonconformality of the Sakai-Sugimoto model.

I discuss a correspondence between a fictitious fluid in the black hole membrane paradigm and highly excited closed string states according to the black hole correspondence principle. I calculate the membrane transport coefficients of an electric Neveu-Schwarz–Neveu-Schwarz 2-charged black hole and transport coefficients of the highly excited closed string states which possess a Kaluza-Klein number and a winding number. Comparing both the transport coefficients at the correspondence point, I show that, except for the bulk viscosity, the membrane transport coefficients are of the same order as the transport coefficients of the closed string states on the stretched horizon. Also, I show that, except for the bulk viscosity, both the dimensionless transport coefficients, which are defined by dividing the transport coefficients by the entropy density, are exactly equal if the central charge is 6.