In the present paper a model of preons and their composites is constructed in the framework of the superstring-inspired flipped $E_6\times {\tilde{E}}_6$ gauge symmetry group which reveals a generalized dual symmetry. Here $E_6$ and ${\tilde{E}}_6$ are nondual and dual sectors of the theory with hyperelectric $g$ and hypermagnetic $\tilde{g}$ charges, respectively. We follow the old idea by J. Pati presuming that preons are dyons, which in our model are confined by hyper-magnetic strings—composite $\mathbf{N}=1$ supersymmetric non-Abelian flux tubes created by the condensation of spreons near the Planck scale. Considering preons belonging to the 27-plet of $E_6$, we have investigated the breakdown of $E_6$ (and ${\tilde{E}}_6$) near the Planck scale into the $SU(6)\times U(1)$ (and $\widetilde{SU(6)}\times \widetilde{U(1)}$) gauge group and shown that the six types of strings having fluxes ${\Phi }_n=n{\Phi }_0$ $(n=\pm 1,\pm 2,\pm 3)$ produce three (and only three) generations of composite quark-leptons and bosons. The model predicts the existence of the Family replicated gauge group $[E_6{]}^3$ near the Planck scale. The runnings of the corresponding fine structure constants are investigated, and the critical coupling constants at the two phase transition points near the Planck scale are calculated. The model explains the hierarchies of masses in the standard model naturally. The compactification in a space-time with five dimensions and its influence on form-factors of composite objects are also briefly discussed.

A universe without weak interactions is constructed that undergoes big-bang nucleosynthesis, matter domination, structure formation, and star formation. The stars in this universe are able to burn for billions of years, synthesize elements up to iron, and undergo supernova explosions, dispersing heavy elements into the interstellar medium. These definitive claims are supported by a detailed analysis where this hypothetical “weakless universe” is matched to our Universe by simultaneously adjusting standard model and cosmological parameters. For instance, chemistry and nuclear physics are essentially unchanged. The apparent habitability of the weakless universe suggests that the anthropic principle does not determine the scale of electroweak breaking, or even require that it be smaller than the Planck scale, so long as technically natural parameters may be suitably adjusted. Whether the multiparameter adjustment is realized or probable is dependent on the ultraviolet completion, such as the string landscape. Considering a similar analysis for the cosmological constant, however, we argue that no adjustments of other parameters are able to allow the cosmological constant to raise up even remotely close to the Planck scale while obtaining macroscopic structure. The fine-tuning problems associated with the electroweak breaking scale and the cosmological constant therefore appear to be qualitatively different from the perspective of obtaining a habitable universe.

The masses of positive parity $[\mathbf{70},0^{+}]$ and $[\mathbf{70},2^{+}]$ nonstrange and strange baryons are calculated in the $1/N_c$ expansion. The approach is based on the separation of a system of $N_c$ quarks into an excited core and an excited quark. The previous work for two flavor baryons is now extended to include strange baryons, to first order in SU(3)-flavor breaking. We show that the extension to $N_f=3$ maintains the regularities previously observed in the behavior of the linear term in $N_c$, of the spin-spin and of the spin-orbit terms. In particular the contribution of the spin-dependent terms decrease with the excitation energy, the dominant term remaining the spin-spin term.

We reconsider the determinations of the strange quark mass $m_s$ from $e^{+}{e}^{-}$ into hadrons data using a new combination of finite energy sum rules (FESR) and revisiting the existing $\tau$-like sum rules by including nonresonant contributions to the spectral functions. To order ${\alpha }_s^3$ and including the tachyonic gluon mass ${\lambda }^2$ contribution, which phenomenologically parametrizes the UV renormalon effect into the perturbative series, we obtain the invariant mass ${\widehat{m}}_s=(119\pm 17)\mathrm{MeV}$ leading to ${\overline{m}}_s(2\mathrm{GeV})=(104\pm 15)\mathrm{MeV}$. Combining this value with the recent and independent phenomenological determinations from some other channels, to order ${\alpha }_s^3$ and including ${\lambda }^2$, we deduce the weighted average ${\overline{m}}_s(2\mathrm{GeV})=(96.1\pm 4.8)\mathrm{MeV}$. The positivity of the spectral functions in the (pseudo)scalar (resp. vector) channels leads to the lower (resp. upper) bounds of ${\overline{m}}_s(2\mathrm{GeV})$: $(71\pm 4)\mathrm{MeV}\le {\overline{m}}_s(2\mathrm{GeV})\le (151\pm 14)\mathrm{MeV}$, to order ${\alpha }_s^3$. Using the chiral perturbation theory (ChPT) mass ratio $r_3\equiv 2m_s/(m_u+m_d)=24.2\pm 1.5$, and the average value of $m_s$, we deduce $({\overline{m}}_u+{\overline{m}}_d)(2\mathrm{GeV})=(7.9\pm 0.6)\mathrm{MeV}$, consistent with the pion sum rule result, which, combined with the ChPT value for $m_u/m_d$, gives ${\overline{m}}_d(2\mathrm{GeV})=(5.1\pm 0.4)\mathrm{MeV}$ and ${\overline{m}}_u(2\mathrm{GeV})=(2.8\pm 0.2)\mathrm{MeV}$. Finally, using $({\overline{m}}_u+{\overline{m}}_d)$ from the pion sum rule and the average value of ${\overline{m}}_s$ (without the pion sum rule), the method gives $r_3=23.5\pm 5.8$, in perfect agreement with the ChPT ratio, indicating the self-consistency of the sum rule results. Using the value ${\overline{m}}_b({\overline{m}}_b)=(4.23\pm 0.06)\mathrm{GeV}$, we also obtain the scale-independent mass ratio $m_b/m_s=50\pm 3$, which is useful for model-buildings. Absolute values of the light quark masses from QCD spectral sum rules reported in this paper are the most accurate determinations to date.

Warm dark matter might more easily account for small scale clustering measurements than the heavier particles typically invoked in $\Lambda$ cold dark matter ($\Lambda \mathrm{CDM}$) cosmologies. In this paper, we consider a $\Lambda \mathrm{WDM}$ cosmology in which sterile neutrinos ${\nu }_s$, with a mass $m_s$ of roughly 1–100 keV, are the dark matter. We use the diffuse x-ray spectrum (total minus resolved point source emission) of the Andromeda galaxy to constrain the rate of sterile neutrino radiative decay: ${\nu }_s\to {\nu }_{e,\mu ,\tau }+\gamma$. Our findings demand that $m_s<3.5\mathrm{keV}$ (95% C.L.) which is a significant improvement over the previous (95% C.L.) limits inferred from the x-ray emission of nearby clusters, $m_s<8.2\mathrm{keV}$ (Virgo A) and $m_s<6.3\mathrm{keV}$ ($\mathrm{\text{Virgo}}\mathrm{A}+\mathrm{\text{Coma}}$).

A study of the $D_{sJ}^{*}(2317{)}^{+}$ and $D_{sJ}(2460{)}^{+}$ mesons in inclusive $c\overline{c}$ production is presented using $232{\mathrm{fb}}^{-1}$ of data collected by the BABAR experiment near $\sqrt{s}=10.6\mathrm{GeV}$. Final states consisting of a $D_s^{+}$ meson along with one or more ${\pi }^0$, ${\pi }^{\pm }$, or $\gamma$ particles are considered. Estimates of the mass and limits on the width are provided for both mesons and for the $D_{s1}(2536{)}^{+}$ meson. A search is also performed for neutral and doubly charged partners of the $D_{sJ}^{*}(2317{)}^{+}$ meson.

We present a search for the flavor-changing neutral current decay $B_s^0\to \varphi {\mu }^{+}{\mu }^{-}$ using about $0.45{\mathrm{fb}}^{-1}$ of data collected in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ with the D0 detector at the Fermilab Tevatron Collider. We find an upper limit on the branching ratio of this decay normalized to $B_s^0\to J/\psi \varphi$ of $\frac{\mathcal{B}(B_s^0\to \varphi {\mu }^{+}{\mu }^{-})}{\mathcal{B}(B_s^0\to J/\psi \varphi )}<4.4\times {10}^{-3}$ at the 95% C.L. Using the central value of the world average branching fraction of $B_s^0\to J/\psi \varphi$, the limit corresponds to $\mathcal{B}(B_s^0\to \varphi {\mu }^{+}{\mu }^{-})<4.1\times {10}^{-6}$ at the 95% C.L., the most stringent upper bound to date.

In a previous paper [Jian-Huang She, J. High Energy Phys. 01 (2006) 002.] using a matrix model, we showed that closed string tachyons can resolve spacelike singularity in one particular class of Misner space (with antiperiodic boundary conditions for fermions around the spatial circle). In this note, we show that for Misner space without closed string tachyons, there also exists a mechanism to resolve the singularity in the context of the matrix model, namely, cosmological winding string production. We show that here space and time also become noncommutative due to these winding strings. Employing the optical theorem, we study the bulk boundary coupling by calculating the four-open-string cylinder amplitudes.

A planar phase space having both position and momentum noncommutativity is defined in a more inclusive setting than that considered elsewhere. The dynamics of a particle in a gravitational quantum well in this space is studied. The use of the WKB approximation and the virial theorem enable analytic discussions on the effect of noncommutativity. Consistent results are obtained following either commutative space or noncommutative space descriptions. Comparison with recent experimental data with cold neutrons at Grenoble imposes an upper bound on the noncommutative parameter. Also, our results are compared with a recent numerical analysis of a similar problem. Finally, we provide a noncommutative version of the virial theorem for the case at hand.

We discuss two classes of semimicroscopic theoretical models of stochastic spacetime foam in quantum gravity and the associated effects on entangled states of neutral mesons, signalling an intrinsic breakdown of $CPT$ invariance. One class of models deals with a specific model of foam, initially constructed in the context of noncritical (Liouville) string theory, but viewed here in the more general context of effective quantum-gravity models. The relevant Hamiltonian perturbation, describing the interaction of the meson with the foam medium, consists of off-diagonal stochastic metric fluctuations, connecting distinct mass eigenstates (or the appropriate generalization thereof in the case of $K$-mesons), and it is proportional to the relevant momentum transfer (along the direction of motion of the meson pair). There are two kinds of $CPT$-violating effects in this case, which can be experimentally disentangled: one (termed “$\omega$-effect”) is associated with the failure of the indistinguishability between the neutral meson and its antiparticle, and affects certain symmetry properties of the initial state of the two-meson system; the second effect is generated by the time evolution of the system in the medium of the spacetime foam, and can result in time-dependent contributions of the $\omega$-effect type in the time profile of the two-meson state. Estimates of both effects are given, which show that, at least in certain models, such effects are not far from the sensitivity of experimental facilities available currently or in the near future. The other class of quantum-gravity models involves a medium of gravitational fluctuations which behaves like a “thermal bath”. In this model both of the above-mentioned intrinsic $CPT$ violation effects are not valid.

In recent work we have shown that a black hole stacked on a brane escapes once it acquires a recoil velocity. This result was obtained in the probe-brane approximation, i.e., when the tension of the brane is negligibly small. Therefore, it is not clear whether the effect of the brane tension may prevent the black hole from escaping for small recoil velocities. The question is whether a critical escape velocity exists. Here, we analyze this problem by studying the interaction between a Dirac-Nambu-Goto brane and a black hole assuming adiabatic (quasistatic) evolution. By describing the brane in a fixed black hole spacetime, which restricts our conclusions to lowest order effects in the tension, we find that the critical escape velocity does not exist for codimension one branes, while it does for higher codimension branes.

We study two steps of moduli stabilization in type IIB flux compactification with gaugino condensations. We consider the condition that one can integrate out heavy moduli first with light moduli remaining. We give appendix, where detail study is carried out for potential minima of the model with a six dimensional compact space with $h_{1,1}=h_{2,1}=1$, including the model, whose respective moduli with $h_{1,1},h_{2,1}\ne 1$ are identified.

We generalize Starobinskiĭ’s stochastic technique to the theory of a massless, minimally coupled scalar interacting with a massless fermion in a locally de Sitter geometry. The scalar is an “active” field that can engender infrared logarithms. The fermion is a passive field that cannot cause infrared logarithms but which can carry them, and which can also induce new interactions between the active fields. The procedure for dealing with passive fields is to integrate them out, then stochastically simplify the resulting effective action following Starobinskiĭ. Because Yukawa theory is quadratic in the fermion this can be done explicitly using the classic solution of Candelas and Raine. We check the resulting stochastic formulation against an explicit two loop computation. We also derive a nonperturbative, leading log result for the stress tensor. Because the scalar effective potential induced by fermions is unbounded below, backreaction from this model might dynamically cancel an arbitrarily large cosmological constant.

We study the Hawking radiation from Rotating black holes from the gravitational anomalies point of view. First, we show that the scalar field theory near the Kerr black hole horizon can be reduced to the 2-dimensional effective theory. Then, following Robinson and Wilczek, we derive the Hawking flux by requiring the cancellation of gravitational anomalies. We also apply this method to Hawking radiation from higher dimensional Myers-Perry black holes. In the appendix, we present the trace anomaly derivation of Hawking radiation to argue the validity of the boundary condition at the horizon.

This is an extended version of our previous letter [S. Iso, H. Umetsu, and F. Wilczek, Phys. Rev. Lett. 96, 151302 (2006).]. In this paper we consider rotating black holes and show that the flux of Hawking radiation can be determined by anomaly cancellation conditions and regularity requirement at the horizon. By using a dimensional reduction technique, each partial wave of quantum fields in a $d=4$ rotating black hole background can be interpreted as a $(1+1)$-dimensional charged field with a charge proportional to the azimuthal angular momentum $m$. From this and the analysis [S. P. Robinson and F. Wilczek, Phys. Rev. Lett. 95, 011303 (2005), S. Iso, H. Umetsu, and F. Wilczek, Phys. Rev. Lett. 96, 151302 (2006).] on Hawking radiation from charged black holes, we show that the total flux of Hawking radiation from rotating black holes can be universally determined in terms of the values of anomalies at the horizon by demanding gauge invariance and general coordinate covariance at the quantum level. We also clarify our choice of boundary conditions and show that our results are consistent with the effective action approach where regularity at the future horizon and vanishing of ingoing modes at $r=\infty$ are imposed (i.e. Unruh vacuum).

Stability analysis of the Kantowski-Sachs type universe in pure higher derivative gravity theory is studied in detail. The nonredundant generalized Friedmann equation of the system is derived by introducing a reduced one-dimensional generalized Kantowski-Sachs type action. Existence and stability of inflationary solution in the presence of higher derivative terms are also studied in detail. Implications to the choice of physical theories are discussed in detail in this paper.

Models with dark energy decaying into dark matter have been proposed to solve the coincidence problem in cosmology. We study the effect of such coupling in the matter power spectrum. Because of the interaction, the growth of matter density perturbations during the radiation dominated regime is slower compared to noninteracting models with the same ratio of dark matter to dark energy today. This effect introduces a damping on the power spectrum at small scales proportional to the strength of the interaction, $c^2$, and similar to the effect generated by ultrarelativistic neutrinos. The interaction also shifts matter-radiation equality to larger scales. We compare the matter power spectrum of interacting quintessence models with the measurments of the 2-degree field galaxy redshift survey (2dFGRS). The data are insensitive to values of $c^2\le {10}^{-3}$ but strongly constrain larger values. We particularize our study to models that during radiation domination have a constant dark matter to dark energy ratio.

We study a class of “landscape” models in which all vacua have positive energy density, so that inflation never ends and bubbles of different vacua are endlessly “recycled.” In such models, each geodesic observer passes through an infinite sequence of bubbles, visiting all possible kinds of vacua. The bubble abundance $p_j$ can then be defined as the frequency at which bubbles of type $j$ are visited along the worldline of an observer. We compare this definition with the recently proposed general prescription for $p_j$ and show that they give identical results.

We show that the gravitino-overproduction problem is prevalent among inflation models in supergravity. An inflaton field $\varphi$ generically acquires (effective) nonvanishing auxiliary field ${\mathcal{G}}_{\Phi }^{(\mathrm{eff})}$, if the Kähler potential is nonminimal. The inflaton field then decays into a pair of the gravitinos. We extensively study the cosmological constraints on ${\mathcal{G}}_{\Phi }^{(\mathrm{eff})}$ for a wide range of the gravitino mass. For many inflation models we explicitly estimate ${\mathcal{G}}_{\Phi }^{(\mathrm{eff})}$, and show that the gravitino-overproduction problem severely constrains the inflation models, unless such an interaction as $K=\kappa /2|\varphi {|}^2{z}^2+\mathrm{H}.\mathrm{c}.$ is suppressed (here $z$ is the field responsible for the supersymmetry breaking). We find that many of them are already excluded or on the verge of, if $\kappa \sim O(1)$.

We present the first fully-nonlinear numerical study of the dynamics of highly-spinning-black-hole binaries. We evolve binaries from quasicircular orbits (as inferred from post-Newtonian theory), and find that the last stages of the orbital motion of black-hole binaries are profoundly affected by their individual spins. In order to cleanly display its effects, we consider two equal-mass holes with individual spin parameters $S/m^2=0.757$, both aligned and antialigned with the orbital angular momentum (and compare with the spinless case), and with an initial orbital period of $125M$. We find that the aligned case completes three orbits and merges significantly after the antialigned case, which completes less than one orbit. The total energy radiated for the former case is $\approx 7\%$ while for the latter it is only $\approx 2\%$. The final Kerr hole remnants have rotation parameters $a/M=0.89$ and $a/M=0.44$ respectively, showing the unlikeliness of creating a maximally rotating black hole out of the merger two highly spinning holes.