We consider the Friedmann-Robertson-Walker cosmologies of theories of gravity that generalize the Einstein-Hilbert action by replacing the Ricci scalar $R$ with some function $f(R)$. The general asymptotic behavior of these cosmologies is found, at both early and late times, and the effects of adding higher and lower powers of $R$ to the Einstein-Hilbert action is investigated. The assumption that the highest powers of $R$ should dominate the Universe’s early history, and that the lowest powers should dominate its future is found to be inaccurate. The behavior of the general solution is complicated, and while it can be the case that single powers of $R$ dominate the dynamics at late times, it can be either the higher or lower powers that do so. It is also shown that it is often the lowest powers of $R$ that dominate at early times, when approach to a bounce or a Tolman solution are generic possibilities. Various examples are considered, and both vacuum and perfect fluid solutions are investigated.

We investigate the influence of primordial perturbations of the energy density and space-time metric on the generation of the lepton and baryon asymmetries. In the weak and strong washout regimes baryon isocurvature perturbations with amplitudes of the same order as those of the cosmic microwave background perturbations are generated on scales of order of the respective Hubble scale. They are, however, washed out by baryon and photon diffusion at the later stages of the universe’s evolution.

We report the results of a recent search for the lowest value of thermal noise that can be achieved in LIGO by changing the shape of mirrors, while fixing the mirror radius and maintaining a low diffractional loss. The result of this minimization is a beam with thermal noise a factor of 2.32 (in power) lower than previously considered Mesa Beams and a factor of 5.45 (in power) lower than the Gaussian beams employed in the current baseline design. Mirrors that confine these beams have been found to be roughly conical in shape, with an average slope approximately equal to the mirror radius divided by arm length, and with mild corrections varying at the Fresnel scale. Such a mirror system, if built, would impact the sensitivity of LIGO, increasing the event rate of observing gravitational waves in the frequency range of maximum sensitivity roughly by a factor of 3 compared to an Advanced LIGO using Mesa beams (assuming all other noises remain unchanged). We discuss the resulting beam and mirror properties and study requirements on mirror tilt, displacement, and figure error, in order for this beam to be used in LIGO detectors.

The Laser Interferometer Space Antenna (LISA) will be the first dedicated space based gravitational wave detector. LISA will consist of a triangular formation of spacecraft, forming an interferometer with $5\times {10}^6\mathrm{km}$ long arms. Annual length variations of the interferometer arms prevent exact laser frequency noise cancellation. Despite prestabilization to an optical cavity the expected frequency noise is many orders of magnitude larger than the required levels. Arm locking is a feedback control method that will further stabilize the laser frequency by referencing it to the $5\times {10}^6\mathrm{km}$ arms. Although the original arm locking scheme produced a substantial noise reduction, the technique suffered from slowly decaying start-up transients and excess noise at harmonic frequencies of the inverse round-trip time. Dual arm locking, presented here, improves on the original scheme by combining information from two interferometer arms for feedback control. Compared to conventional arm locking, dual arm locking exhibits significantly reduced start-up transients, no noise amplification at frequencies within the LISA signal band, and more than 50 fold improvement in noise suppression at low frequencies. In this article we present a detailed analysis of the dual arm locking control system and present simulation results showing a noise reduction of 10 000 at a frequency of 10 mHz.

It is shown that the stratified or “doubly lopsided” mass matrix structure that is known to reproduce well the qualitative features of the quark and lepton masses and mixings can arise quite naturally in the context of grand unification based on the groups $SU(N)$ with $N>5$. An $SU(8)$ example is constructed with the minimal anomaly free, three-family set of fermions, in which a realistic flavor structure results without flavor symmetry.

We computed potentials between static color sources from the six lowest representations of ${\mathrm{G}}_2$ lattice gauge theory, in numerical simulations with the Wilson action on asymmetric lattices with nonperturbatively estimated values of the bare anisotropy. We present evidence for (approximate) Casimir scaling of the obtained intermediate string tensions. The agreement with the Casimir-scaling prediction improves by increasing the coupling $\beta$ in the weak-coupling region above the crossover observed in ${\mathrm{G}}_2$ gauge theory. The result naturally fits into confinement models with magnetic disorder and vacuum domain structure, but may represent a challenge for other approaches.

Using the “quality factor” method, we analyze the scaling properties of deep inelastic processes at the accelerator HERA and fixed target experiments for $x\le {10}^{-2}$. We look for scaling formulas of the form ${\sigma }^{{\gamma }^{*}p}(\tau )$, where $\tau (L=\log Q^2,Y)$ is a scaling variable suggested by the asymptotic properties of QCD evolution equations with rapidity $Y$. We consider four cases: “fixed coupling,” corresponding to the original geometric scaling proposal and motivated by the asymptotic properties of the Balitsky-Kovchegov equation with fixed QCD coupling constant; two versions, “running coupling I, II,” of the scaling suggested by the Balitsky-Kovchegov equation with running coupling; and “diffusive scaling” suggested by the QCD evolution equation with Pomeron loops. The quality factors, quantifying the phenomenological validity of the candidate scaling variables, are fitted on the total and deeply virtual Compton scattering cross-section data from HERA and predictions are made for the elastic vector meson and for the diffractive cross sections at fixed small $x_{\mathbb{P}}$ or $\beta$. The first three scaling formulas have comparably good quality factors while the fourth one is disfavored. Adjusting initial conditions gives a significant improvement of the running coupling II scaling.

Since all couplings of the exotic ${\Theta }^{+}$ baryon to normal hadrons seem to be small it is hard to reveal it in standard resonance searching. We suggest looking for the ${\Theta }^{+}$ production in interference with a known resonance yielding the same final state but having a high production rate. The interference production cross section is linear in the ${\Theta }^{+}$ couplings whereas the noninterference cross section is quadratic. That gives an obvious gain if the couplings are small. Moreover, employing the peculiar oscillating nature of the interference processes one can reduce the parasitic background and determine the ${\Theta }^{+}$ resonance parameters.

The vector meson $\omega \mathrm{\text{−}}\varphi$ mixing is studied in two alternative scenarios with different numbers of mixing angles, i.e., the one-mixing-angle scenario and the two-mixing-angle scenario, in both the octet-singlet mixing scheme and the quark flavor mixing scheme. Concerning the reproduction of experimental data and the $Q^2$ behavior of transition form factors, the one-mixing-angle scenario in the quark flavor scheme performs better than that in the octet-singlet scheme, while the two-mixing-angle scenario works well for both mixing schemes. The difference between the two mixing angles in the octet-singlet scheme is bigger than that in the quark flavor scheme.

The $\eta$ transitions of ${\rm Y}(4S,5S)$ into ${\rm Y}(1S,2S)$ are studied in the rescattering model by considering the final state interactions above the $B\overline{B}$ threshold. The width of the $\eta$ transition of ${\rm Y}(4S)$ into ${\rm Y}(1S)$ is found to be larger than that of the dipion transition, and the ratio of $\Gamma ({\rm Y}(4S)\to {\rm Y}(1S)\eta )$ to $\Gamma ({\rm Y}(4S)\to {\rm Y}(1S){\pi }^{+}{\pi }^{-})$ is predicted to be $R_4=1.8-4.5$, which is about 2 orders of magnitude larger than the expectation of the conventional hadronic transition theory, and is supported by the new BABAR measurement. The widths of the $\eta$ transitions of ${\rm Y}(5S)$ are found to be sensitive to the coupling constants $g_{{\rm Y}(5S)B^{(*)}{B}^{(*)}}$ due to a large cancellation between contributions from the $B\overline{B}$, $B^{*}\overline{B}+\mathrm{c}.\mathrm{c}.$, and $B^{*}{\overline{B}}^{*}$ channels, and only a rough estimate $\Gamma ({\rm Y}(5S)\to {\rm Y}(1S,2S)\eta )=10–200\mathrm{KeV}$ can be given. The widths of the ${\eta }^{\prime }$ transitions of ${\rm Y}(4S,5S)$ are also discussed, and they could be much smaller than that of the corresponding $\eta$ transitions mainly due to the tiny phase space.

We examine the possibility that a certain class of neutrino mass matrices, namely, those with two independent vanishing minors in the flavor basis, regardless of being invertible or not, is sufficient to describe current data. We compute generic formulas for the ratios of the neutrino masses and for the Majorana phases. We find that seven textures with two vanishing minors can accommodate the experimental data. We present an estimate of the mass matrix for these patterns. All of the possible textures can be dynamically generated through the seesaw mechanism augmented with a discrete Abelian symmetry.

We explore the potential offered by large-mass liquid argon detectors for determination of the sign of $\Delta m_{31}^2$, or the neutrino mass hierarchy, through interactions of atmospheric neutrinos. We give results for a 100 kT sized magnetized detector which provides separate sensitivity to ${\nu }_{\mu }$, ${\overline{\nu }}_{\mu }$ and, over a limited energy range, to ${\nu }_e$, ${\overline{\nu }}_e$. We also discuss the sensitivity for the unmagnetized version of such a detector. After including the effect of smearing in neutrino energy and direction and incorporating the relevant statistical, theoretical, and systematic errors, we perform a binned ${\chi }^2$ analysis of simulated data. The ${\chi }^2$ is marginalized over the presently allowed ranges of neutrino parameters and determined as a function of ${\theta }_{13}$. We find that such a detector offers superior capabilities for hierarchy resolution, allowing a $>4\sigma$ determination for a 100 kT detector over a 10-year running period for values of ${sin}^{2}2{\theta }_{13}\ge 0.05$. For an unmagnetized detector, a $2.5\sigma$ hierarchy sensitivity is possible for ${sin}^{2}2{\theta }_{13}=0.04$.

We present a measurement of the branching fractions for the Cabibbo-favored radiative decay $D^0\to {\overline{K}}^{*0}\gamma$ and the Cabibbo-suppressed radiative decay $D^0\to \varphi \gamma$. These measurements are based on a data sample corresponding to an integrated luminosity of $387.1{\mathrm{fb}}^{-1}$ and recorded with the BABAR detector at the PEP-II $e^{+}{e}^{-}$ asymmetric-energy collider operating at center-of-mass energies 10.58 and 10.54 GeV. We measure the branching fractions relative to the well-studied decay $D^0\to K^{-}{\pi }^{+}$ and find $\mathcal{B}(D^0\to {\overline{K}}^{*0}\gamma )/\mathcal{B}(D^0\to K^{-}{\pi }^{+})=(8.43\pm 0.51\pm 0.70)\times {10}^{-3}$ and $\mathcal{B}(D^0\to \varphi \gamma )/\mathcal{B}(D^0\to K^{-}{\pi }^{+})=(7.15\pm 0.78\pm 0.69)\times {10}^{-4}$, where the first error is statistical and the second is systematic. This is the first observation of the decay mode $D^0\to {\overline{K}}^{*0}\gamma$.

Using the solitonic solution-generating techniques, we generate a new exact solution which describes a pair of rotating black holes on a Kaluza-Klein bubble as a vacuum solution in the five-dimensional Kaluza-Klein theory. We also investigate the properties of this solution. Two black holes with topology $S^3$ are rotating along the same direction even though the directions of intrinsic spin of the black holes are different. The bubble plays a role in holding two black holes. In the static case, it coincides with the solution found by Elvang and Horowitz.

We reply to Creutz’s comments on our paper “’t Hooft vertices, partial quenching, and rooted staggered QCD.” We show that his criticisms are incorrect and result from a misunderstanding both of our work, and of the related work of Adams.

A recent criticism of the proof of the failure of the rooting procedure with staggered fermions is shown to be incorrect.

In this study, we propose new Higgs production mechanisms with multiphoton final states in the fermiophobic limit of the two Higgs doublet model. The processes are: $gg\to hh$, $gg\to Hh$ followed by $H\to hh$ and $gg\to Ah$ followed by $A\to hZ$. In the fermiophobic limit, $gg\to hh$ and $gg\to Ah\to hhZ$ would give rise to $4\gamma$ signature while $gg\to Hh\to hhh$ can give a $6\gamma$ final state. We show that both the Fermilab Tevatron and CERN’s Large Hadron Collider can probe a substantial slice of the parameter space in this fermiophobic scenario of the two Higgs doublet model. If observed the above processes can give some information on the triple Higgs couplings involved.

We compute radiative correction to the lightest neutral Higgs mass ($m_h$) induced by the Kaluza-Klein (KK) towers of fermions and sfermions in a minimal supersymmetric scenario embeded in a 5-dimensional warped space. The Higgs is confined to the TeV brane. The KK spectra of matter supermultiplets is tied to the explanation of the fermion mass hierarchy problem. We demonstrate that for a reasonable choice of extra-dimensional parameters, the KK-induced radiative correction can enhance the upper limit on $m_h$ by as much as 100 GeV beyond the 4d limit of 135 GeV.