We consider the possible existence of self-similar solutions containing black holes in a Friedmann background with a stiff fluid or a scalar field. We carefully study the relationship between the self-similar equations in these two cases and emphasize the crucial role of the similarity horizon. We show that there is no self-similar black hole solution surrounded by an exact or asymptotically flat Friedmann background containing a massless scalar field. This result also applies for a scalar field with a potential, providing the universe is decelerating. However, if there is a potential and the universe is accelerating (as in the quintessence scenario), the result only applies for an exact Friedmann background. This extends the result previously found in the stiff fluid case and strongly suggests that accretion onto primordial black holes is ineffective even during scalar field domination. It also contradicts recent claims that such black holes can grow appreciably by accreting quintessence. Appreciable growth might be possible with very special matter fields but this requires ad hoc and probably unphysical conditions.

Recent spectroscopic observations of metal-poor stars have indicated that both ${}^7\mathrm{Li}$ and ${}^6\mathrm{Li}$ have abundance plateaus with respect to the metallicity. Abundances of ${}^7\mathrm{Li}$ are about a factor three lower than the primordial abundance predicted by standard big bang nucleosynthesis (SBBN), and ${}^6\mathrm{Li}$ abundances are $\sim 1/20$ of ${}^7\mathrm{Li}$, whereas SBBN predicts negligible amounts of ${}^6\mathrm{Li}$ compared to the detected level. These discrepancies suggest that ${}^6\mathrm{Li}$ has another cosmological or Galactic origin than the SBBN. Furthermore, it would appear that ${}^7\mathrm{Li}$ (and also ${}^6\mathrm{Li}$) has been depleted from its primordial abundance by some post-BBN processes. In this paper we study the possibility that the radiative decay of long-lived particles has affected the cosmological lithium abundances. We calculate the nonthermal nucleosynthesis associated with the radiative decay taking account both of the primary nuclear production reactions and the effects of secondary production as well as the destruction processes of energetic nuclides $\mathrm{D}$, $\mathrm{T}$, ${}^3\mathrm{He}$, ${}^4\mathrm{He}$, ${}^6\mathrm{Li}$, and ${}^7\mathrm{Li}$. We explore the allowed region of the parameters specifying the properties of long-lived particles. We also impose constraints from observations of the CMB energy spectrum. We find that nonthermal nucleosynthesis produces ${}^6\mathrm{Li}$ at the level detected in metal-poor halo stars (MPHSs), when the lifetime of the unstable particles is of the order $\sim {10}^8–{10}^{12}\mathrm{s}$ and their initial abundance with respect to that of the photons is $\sim ({10}^{-13}–{10}^{-12}\mathrm{GeV})/E_{\gamma 0}$, where $E_{\gamma 0}$ is the emitted photon energy in the radiative decay. We conclude that the most likely nucleosynthetic scenario involves two different processes. First, a nonthermal cosmological nucleosynthesis associated with the radiative decay of unstable particles; and second, the stellar depletion of both of the primordial lithium isotopic abundances.

We study the implication of the recent $\Delta M_s$ measurement on $b\to s\overline{q}q$ transitions. We show that it is possible, in the presence of a flavor symmetry, that the phase in $B_s$ mixing may be unobservable even with new $CP$ odd phases in $b\to s$ transitions. These phases may then produce new $CP$ odd effects in certain $b\to s\overline{q}q$ transitions like $B\to K\pi$ but not in others like $B_d\to \varphi K_s$. Working in a two Higgs doublet model of new physics we discuss the allowed NP contribution to $B\to K\pi$ and $B_d\to \varphi K_s$ decays with the new $\Delta M_s$ measurement.

We study the phase space for neutrino emissions with massive quarks in direct Urca processes in normal and color-superconducting quark matter. We derive in QCD and the Nambu-Jona-Lasinio model the Fermi momentum reduction resulting from Fermi liquid properties which opens up the phase space for neutrino emissions. The relation between the Fermi momentum and chemical potential is found to be $p_F\approx \mu (1-\kappa )$ with $\kappa$ depending on coupling constants. We find in the weak coupling regime that $\kappa$ is a monotonically increasing function of the chemical potential. This implies quenched phase space for neutrino emissions at low baryon densities. We calculate neutrino emissivities with massive quarks in a spin-one color superconductor. The quark mass corrections are found to be of the same order as the contributions in the massless case, which will bring sizable effects on the cooling behavior of compact stars.

We report a search for the $h_c$ meson via the decay chain $B^{\pm }\to h_c{K}^{\pm }$, $h_c\to {\eta }_c\gamma$ with ${\eta }_c\to K_S^0{K}^{\pm }{\pi }^{\mp }$ and $p\overline{p}$. No significant signals are observed. We obtain upper limits on the branching fractions for $B^{\pm }\to {\eta }_c\gamma K^{\pm }$ in bins of the ${\eta }_c\gamma$ invariant mass. The results are based on an analysis of $253{\mathrm{fb}}^{-1}$ of data collected by the Belle detector at the KEKB $e^{+}{e}^{-}$ collider.

I study the leading effects of discretization errors on the low-energy part of the spectrum of the Hermitian Wilson-Dirac operator in infinite volume. The method generalizes that used to study the spectrum of the Dirac operator in the continuum, and uses partially quenched chiral perturbation theory for Wilson fermions. The leading-order corrections are proportional to $a^2$ ($a$ being the lattice spacing). At this order, I find that the method works only for one choice of sign of one of the three low-energy constants describing discretization errors. If these constants have the relative magnitudes expected from large $N_c$ arguments, then the method works if the theory has an Aoki phase for $m\sim a^2$, but fails if there is a first-order transition. In the former case, the dependence of the gap and the spectral density on $m$ and $a^2$ are determined. In particular, the gap is found to vanish more quickly as $m_{\pi }^2\to 0$ than in the continuum. This reduces the region where simulations are safe from fluctuations in the gap.

I report on a numerical program, which can be used to calculate any infrared safe two-jet observable in electron-positron annihilation to next-to-next-to-leading order in the strong coupling constant ${\alpha }_s$. The calculation is based on the subtraction method. The result for the two-jet cross section is compared to the literature.

We propose a simple but useful parametrization of the flavor composition of ultrahigh-energy neutrino fluxes produced from distant astrophysical sources: ${\varphi }_e:{\varphi }_{\mu }:{\varphi }_{\tau }={sin}^2\xi {cos}^2\zeta :{cos}^2\xi {cos}^2\zeta :{sin}^2\zeta$. We show that it is possible to determine or constrain $\xi$ and $\zeta$ by observing two independent neutrino flux ratios at the second-generation neutrino telescopes, provided three neutrino mixing angles and the Dirac $CP$-violating phase have been well measured in neutrino oscillations. Any deviation of $\zeta$ from zero will signify the existence of cosmic ${\nu }_{\tau }$ and ${\overline{\nu }}_{\tau }$ neutrinos at the source, and an accurate value of $\xi$ can be used to test both the conventional mechanism and the postulated scenarios for cosmic neutrino production.

It is known that neutrino oscillations may map ${\varphi }_e:{\varphi }_{\mu }:{\varphi }_{\tau }=1:2:0$, the initial flavor ratios of ultrahigh-energy neutrino fluxes produced from a distant astrophysical source, into ${\varphi }_e^{\mathrm{D}}:{\varphi }_{\mu }^{\mathrm{D}}:{\varphi }_{\tau }^{\mathrm{D}}=1:1:1$ at the detector of a neutrino telescope. We remark that this naive expectation is only valid in the $\mu \mathrm{\text{−}}\tau$ symmetry limit, in which two neutrino mixing angles satisfy ${\theta }_{13}=0$ and ${\theta }_{23}=\pi /4$. Allowing for the slight breaking of $\mu \mathrm{\text{−}}\tau$ symmetry, we find ${\varphi }_e^{\mathrm{D}}:{\varphi }_{\mu }^{\mathrm{D}}:{\varphi }_{\tau }^{\mathrm{D}}=(1-2\Delta ):(1+\Delta ):(1+\Delta )$ with $\Delta$ characterizing the combined effect of ${\theta }_{13}\ne 0$ and ${\theta }_{23}\ne \pi /4$. Current neutrino oscillation data indicate $-0.1\lesssim \Delta \lesssim +0.1$. We also look at the possibility to probe $\Delta$ by detecting the ${\overline{\nu }}_e$ flux of $E_{{\overline{\nu }}_e}\approx 6.3\mathrm{PeV}$ via the Glashow resonance channel ${\overline{\nu }}_{e}e\to W^{-}\to \mathrm{\text{anything}}$.

We compute the complete electroweak one-loop effect on the process of $t$-channel single top production at LHC in the standard model and in the MSSM within the mSUGRA symmetry breaking scheme. We find that the one-loop electroweak SM effect is large, and decreases the cross section of an amount that is of the same size as that of the NLO QCD one. The genuine SUSY effect in the mSUGRA scheme, for a general choice of benchmark points, is rather small. It might become large and visible in more general scenarios around thresholds involving light stop and neutralino mass values.

We have performed a high resolution search for galactic halo axions in cold flows using a microwave cavity detector. The analysis procedure and other details of this search are described. No axion signal was found in the mass range $1.98–2.17\mu \mathrm{eV}$. We place upper limits on the density of axions in local discrete flows based on this result.

The recent NA48/2 improvement on $R_K=\Gamma (K\to e\nu )/\Gamma (K\to \mu \nu )$ emphasizes the role of $K_{l2}$ decays in probing the $\mu -e$ universality. Supersymmetric (SUSY) extensions of the Standard Model can exhibit $\mu -e$ nonuniversal contributions. Their origin is twofold: those deriving from lepton flavor conserving couplings are subdominant with respect to those arising from lepton flavor violating (LFV) sources. We show that $\mu -e$ nonuniversality in $K_{\ell 2}$ is quite effective in constraining relevant regions of SUSY models with LFV (for instance, supergravities with a see-saw mechanism for neutrino masses). A comparison with analogous bounds coming from $\tau$ LFV decays proves the relevance of the measurement of $R_K$ to probe LFV in SUSY.

In this paper we investigate the Wightman function, the renormalized vacuum expectation values of the field square, and the energy-momentum tensor for a massive scalar field with general curvature coupling inside and outside of a cylindrical shell in the generalized spacetime of straight cosmic string. For the general case of Robin boundary condition, by using the generalized Abel-Plana formula, the vacuum expectation values are presented in the form of the sum of boundary-free and boundary-induced parts. The asymptotic behavior of the vacuum expectation values of the field square, energy density, and stresses are investigated in various limiting cases. The generalization of the results to the exterior region is given for a general cylindrically symmetric static model of the string core with finite support.

In a recent paper Jones and Mateo used operator techniques to show that the non-Hermitian $\mathcal{P}\mathcal{T}$-symmetric wrong-sign quartic Hamiltonian $H=\frac{1}{2}{p}^2-g{x}^4$ has the same spectrum as the conventional Hermitian Hamiltonian $\tilde{H}=\frac{1}{2}{p}^2+4g{x}^4-\sqrt{2g}x$. Here, this equivalence is demonstrated very simply by means of differential-equation techniques and, more importantly, by means of functional-integration techniques. It is shown that the linear term in the Hermitian Hamiltonian is anomalous; that is, this linear term has no classical analog. The anomaly arises because of the broken parity symmetry of the original non-Hermitian $\mathcal{P}\mathcal{T}$-symmetric Hamiltonian. This anomaly in the Hermitian form of a $\mathcal{P}\mathcal{T}$-symmetric quartic Hamiltonian is unchanged if a harmonic term is introduced into $H$. When there is a harmonic term, an immediate physical consequence of the anomaly is the appearance of bound states; if there were no anomaly term, there would be no bound states. Possible extensions of this work to $-{\varphi }^4$ quantum field theory in higher-dimensional space-time are discussed.

Although the observed universe appears to be geometrically flat, it could have one of 18 global topologies. A constant-time slice of the spacetime manifold could be a torus, Möbius strip, Klein bottle, or others. This global topology of the universe imposes boundary conditions on quantum fields and affects the vacuum energy density via the Casimir effect. In a spacetime with such a nontrivial topology, the vacuum energy density is shifted from its value in a simply connected spacetime. In this paper, the vacuum expectation value of the stress-energy tensor for a massless scalar field is calculated in all 17 multiply connected, flat, and homogeneous spacetimes with different global topologies. It is found that the vacuum energy density is lowered relative to the Minkowski vacuum level in all spacetimes and that the stress-energy tensor becomes position-dependent in spacetimes that involve reflections and rotations.

A cosmological model that aims at solving the coincidence problem should show that dark energy and dark matter follow the same scaling solution from some time onward. At the same time, the model should contain a sufficiently long matter-dominated epoch that takes place before acceleration in order to guarantee a decelerated epoch and structure formation. So a successful cosmological model requires the occurrence of a sequence of epochs, namely, a radiation era, a matter-dominated era, and a final accelerated scaling attractor with ${\Omega }_{\phi }\simeq 0.7$. In this paper we derive the generic form of a scalar-field Lagrangian that possesses scaling solutions in the case where the coupling $Q$ between dark energy and dark matter is a free function of the field $\phi$. We then show, rather surprisingly, that the aforementioned sequence of epochs cannot occur for a vast class of generalized coupled scalar-field Lagrangians that includes, to our knowledge, all scaling models in the current literature.

We apply the standard theory of the elastic body to obtain a set of equations describing the behavior of an acoustic gravitational wave detector, fully taking into account the three-dimensional properties of the mass, the readout, and the signal. We show that the advantages given by a dual detector made by two nested oscillators also can be obtained by monitoring two different acoustic modes of the same oscillator, thus easing the detector realization. We apply these concepts and by means of an optimization process we derive the main figures of such a single mass dual detector designed specifically for the frequency interval 2–5 kHz. Finally we calculate the standard quantum limit sensitivity of this detector.

After a brief review and a renewed analysis of some relevant analyticity properties (when going from Minkowskian to Euclidean theory) of the high-energy parton-parton and hadron-hadron scattering amplitudes in gauge theories, described nonperturbatively, in the eikonal approximation, by certain correlation functions of two Wilson lines or two Wilson loops near the light cone, we shall see how these same properties lead to a nice geometrical interpretation of the crossing symmetry between quark-quark and quark-antiquark eikonal amplitudes and also between loop-loop eikonal amplitudes. This relation between Minkowskian-to-Euclidean analyticity properties and crossing symmetry is discussed in detail and explicitly tested in the first orders of perturbation theory. Some nonperturbative examples existing in the literature are also discussed.

We implement the mechanism of spontaneous $CP$ violation in the 3-3-1 model with right-handed neutrinos and recognize their sources of $CP$ violation. Our main result is that the mechanism works already in the minimal version of the model and new sources of $CP$ violation emerges as an effect of new physics at energies higher than the electroweak scale.

We investigate the continuum limit of the rooted staggered determinant in the 2-dimensional Schwinger model. We match both the unrooted and rooted staggered determinants with an overlap fermion determinant of two (one) flavors and a local pure gauge effective action by fitting the coefficients of the effective action and the mass of the overlap operator. The residue of this fit measures the difference of the staggered and overlap fermion actions. We show that this residue scales at least as $O(a^2)$, implying that any difference, be it local or nonlocal, between the staggered and overlap actions becomes irrelevant in the continuum limit. For the model under consideration here, this observation justifies the rooting procedure for the staggered sea quark action.