We apply the postquasistatic approximation to study the evolution of spherically symmetric fluid distributions undergoing dissipation in the form of radial heat flow. For a model that corresponds to an incompressible fluid departing from the static equilibrium, it is not possible to go far from the initial state after the emission of a small amount of energy. Initially collapsing distributions of matter are not permitted. Emission of energy can be considered as a mechanism to avoid the collapse. If the distribution collapses initially and emits one hundredth of the initial mass only the outermost layers evolve. For a model that corresponds to a highly compressed Fermi gas, only the outermost shell can evolve with a shorter hydrodynamic time scale.

In a landscape with metastable minima, the bubbles will inevitably nucleate. We show that when the bubbles collide, due to the dramatic oscillation of the field at the collision region, the energy deposited in the bubble walls can be efficiently released by the explosive production of the particles. In this sense, the collision of bubbles is actually highly inelastic. The cosmological implications of this result are discussed.

The deformed $z=2$ Hořava-Lifshitz gravity with coupling constant $\omega$ leads to a nonrelativistic mixmaster cosmological model. The potential of theory is given by the sum of IR and UV potentials in the ADM Hamiltonian formalism. It turns out that adding the UV potential cannot suppress chaotic behaviors existing in the IR potential.

Energetic positrons produced in annihilation or decay of dark matter particles in the Milky Way can serve as an important indirect signature of dark matter. Computing the positron flux expected in a given dark matter model involves solving transport equations, which account for interaction of positrons with matter and galactic magnetic fields. Existing calculations solve the equations inside the diffusion zone, where galactic magnetic fields confine positrons, and assume vanishing positron density on the boundaries of this zone. However, in many models, a substantial fraction of the dark matter halo lies outside the diffusion zone. Positrons produced there can then enter the diffusion zone and get trapped, potentially reaching the Earth and increasing the expected flux. We calculate this enhancement for a variety of models. We also evaluate the expected enhancement of the flux of energetic photons produced by the inverse Compton scattering of the extra positrons on starlight and cosmic microwave background. We find maximal flux enhancements of order 20% in both cases.

We study the possible decay of a coherently oscillating scalar field, interpreted as dark matter, into light fermions. Specifically, we consider a scalar field with sub-eV mass decaying into a Fermi sea of neutrinos. We recognize the similarity between our scenario and inflationary preheating where a coherently oscillating scalar field decays into standard model particles. Like the case of fermionic preheating, we find that Pauli blocking controls the dark matter decay into the neutrino sea. The radius of the Fermi sphere depends on the expansion of the universe leading to a time varying equation of state of dark matter. This makes the scenario very rich and we show that the decay rate might be different at different cosmological epochs. We categorize this in two interesting regimes and then study the cosmological perturbations to find the impact on structure formation. We find that the decay may help in alleviating some of the standard problems related to cold dark matter.

The angular, spectral, and temporal features of the highest energy protons and, accompanying them, secondary neutrinos and synchrotron gamma rays propagating through the intergalactic magnetic and radiation fields are studied using the analytical solutions of the Boltzmann transport equation obtained in the limit of the small-angle and continuous-energy-loss approximation.

The Pierre Auger (cosmic ray) Observatory provides a laboratory for studying fundamental physics at energies far beyond those available at colliders. The Observatory is sensitive not only to hadrons and photons but can in principle detect ultrahigh energy neutrinos in the cosmic radiation. Interestingly, it may be possible to uncover new physics by analyzing characteristics of the neutrino flux at the Earth. By comparing the rate for quasihorizontal, deeply penetrating air showers triggered by all types of neutrinos with the rate for slightly up-going showers generated by Earth-skimming tau neutrinos, we determine the ratio of events which would need to be detected in order to signal the existence of new nonperturbative interactions beyond the TeV scale in which the final state energy is dominated by the hadronic component. We use detailed Monte Carlo simulations to calculate the effects of interactions in the Earth and in the atmosphere. We find that observation of 1 Earth skimming and 10 quasihorizontal events would exclude the standard model at the 99% confidence level. If new nonperturbative physics exists, a decade or so would be required to find it in the most optimistic case of a neutrino flux at the Waxman-Bahcall level and a neutrino-nucleon cross section an order of magnitude above the standard model prediction.

The scientific objectives of the LISA Technology Package experiment on board of the LISA Pathfinder mission demand accurate calibration and validation of the data analysis tools in advance of the mission launch. The level of confidence required in the mission outcomes can be reached only by intensively testing the tools on synthetically generated data. A flexible procedure allowing the generation of a cross-correlated stationary noise time series was set up. A multichannel time series with the desired cross-correlation behavior can be generated once a model for a multichannel cross-spectral matrix is provided. The core of the procedure comprises a noise coloring, multichannel filter designed via a frequency-by-frequency eigendecomposition of the model cross-spectral matrix and a subsequent fit in the $Z$ domain. The common problem of initial transients in a filtered time series is solved with a proper initialization of the filter recursion equations. The noise generator performance was tested in a two-dimensional case study of the closed-loop LISA Technology Package dynamics along the two principal degrees of freedom.

We show the advantages of a wedding cake design for Sunyaev-Zel’dovich cluster surveys. We show that by dividing up a cluster survey into a wide and deep survey, one can essentially recover the cosmological information that would be diluted in a single survey of the same duration due to the uncertainties in our understanding of cluster physics. The parameter degeneracy directions of the deep and wide surveys are slightly different, and combining them breaks these degeneracies effectively. A variable depth survey with a few thousand clusters is as effective at constraining cosmological parameters as a single depth survey with a much larger cluster sample.

We have analyzed the early LHC signatures of the minimal supergravity (mSUGRA) model. Our emphasis is on the 7-TeV run corresponding to an integrated luminosity of $\sim 1.0{\mathrm{fb}}^{-1}$ although we have also discussed briefly the prospects at LHC-10 TeV. We focus on the parameter space yielding relatively light squark and gluinos consistent with the dark matter relic density data and the LEP bounds on the lightest Higgs scalar mass. This parameter space is only allowed for nonvanishing trilinear soft breaking term $A_0$. A significant region of the parameter space with large to moderate negative values of $A_0$ consistent with the stability of the scalar potential and relic density production via neutralino annihilation and/or neutralino—stau coannihilation yields observable signal via the $\mathrm{\text{jets}}+\mathrm{\text{missing transverse}}$ energy channel. The one $\mathrm{\text{lepton}}+\mathrm{\text{jets}}+\mathrm{\text{missing energy}}$ signal is also viable over a smaller but nontrivial parameter space. The ratio of the size of the two signals—free from theoretical uncertainties—may distinguish between different relic density generating mechanisms. With efficient $\tau$-tagging facilities at 7 TeV, the discriminating power may increase significantly. We also comment on other dark matter relic density allowed mSUGRA scenarios and variants thereof in the context of LHC-7 TeV.

We present results on the omega baryon (${\Omega }^{-}$) electromagnetic form factors using $N_f=2+1$ domain-wall fermion configurations for three pion masses in the range of about 350 to 300 MeV. We compare results obtained using domain-wall fermions with those of a mixed-action (hybrid) approach, which combines domain-wall valence quarks on staggered sea quarks, for a pion mass of about 350 MeV. We pay particular attention in the evaluation of the subdominant electric quadrupole form factor to sufficient accuracy to exclude a zero value, by constructing a sequential source that isolates it from the dominant form factors. The ${\Omega }^{-}$ magnetic moment, ${\mu }_{{\Omega }^{-}}$, and the electric charge and magnetic radius, $⟨r_{E0/M1}^2⟩$, are extracted for these pion masses. The electric quadrupole moment is determined for the first time using dynamical quarks.

We present lattice simulations of a center-symmetric dimensionally reduced effective field theory for SU(2) Yang-Mills which employ thermal Wilson lines and three-dimensional magnetic fields as fundamental degrees of freedom. The action is composed of a gauge invariant kinetic term, spatial gauge fields and a potential for the Wilson line which includes a fuzzy bag term to generate nonperturbative fluctuations. The effective potential for the Polyakov loop is extracted from the simulations including all modes of the loop as well as for cooled configurations where the hard modes have been averaged out. The former is found to exhibit a nonanalytic contribution while the latter can be described by a mean field like ansatz with quadratic and quartic terms, plus a Vandermonde potential which depends upon the location within the phase diagram.

We have revisited glueball mixing with the pseudoscalar mesons in the MIT bag model scheme. The calculation has been performed in the spherical cavity approximation to the bag using two different fermion propagators, the cavity and the free propagators. We obtain probabilities of mixing for the $\eta$ at the level of 0.006%–2.0%, while for the ${\eta }^{\prime }$ one at the level of 0.6%–40%, depending on the choice of bag radius and, therefore, of the strong coupling constant. Our results differ from previous calculations. The origin of our difference stems from the treatment of the time integrations. The comparison of our calculation with experimental data, which is consistent with small $\eta -{\eta }^{\prime }-G$ mixing, implies that the pseudoscalar glueball is small, $R\sim 0.5–0.6\mathrm{fm}$ and has a large mass, $M_G\sim 2000–2500\mathrm{MeV}$.

We report the measurement of $\nu \mathrm{\text{−}}e$ elastic scattering from ${}^8\mathrm{B}$ solar neutrinos with 3 MeV energy threshold by the Borexino detector in Gran Sasso (Italy). The rate of solar neutrino-induced electron scattering events above this energy in Borexino is $0.22\pm 0.04(\mathrm{stat})\pm 0.01(\mathrm{syst})\mathrm{cpd}/100\mathrm{t}$, which corresponds to ${\Phi }_{{}^8\mathrm{B}}^{\mathrm{ES}}=2.4\pm 0.4\pm 0.1\times {10}^6{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}$, in good agreement with measurements from SNO and SuperKamiokaNDE. Assuming the ${}^8\mathrm{B}$ neutrino flux predicted by the high metallicity standard solar model, the average ${}^8\mathrm{B}$ ${\nu }_e$ survival probability above 3 MeV is measured to be $0.29\pm 0.10$. The survival probabilities for ${}^7\mathrm{Be}$ and ${}^8\mathrm{B}$ neutrinos as measured by Borexino differ by $1.9\sigma$. These results are consistent with the prediction of the MSW-LMA solution of a transition in the solar ${\nu }_e$ survival probability $P_{ee}$ between the low-energy vacuum-driven and the high-energy matter-enhanced solar neutrino oscillation regimes.

We explore the consequences of assuming that the neutrino mass matrix is a linear combination of the matrices of a three-dimensional representation of the group $S_3$ and that it has one zero mass eigenvalue. When implemented, these two assumptions allow us to express the transformation matrix relating the mass eigenstates to the flavor eigenstates in terms of a single parameter which we fit to the available data.

Neutrino-electron scatterings are purely leptonic processes with robust standard model (SM) predictions. Their measurements can therefore provide constraints to physics beyond SM. The ${\overline{\nu }}_{\mathrm{e}}-\mathrm{e}$ data taken at the Kuo-Sheng Reactor Neutrino Laboratory were used to probe two scenarios: nonstandard neutrino interactions (NSI) and unparticle physics. New constraints were placed on the NSI parameters $({\epsilon }_{\mathrm{ee}}^{\mathrm{eL}},{\epsilon }_{\mathrm{ee}}^{\mathrm{eR}})$, $({\epsilon }_{\mathrm{e}\mu }^{\mathrm{eL}},{\epsilon }_{\mathrm{e}\mu }^{\mathrm{eR}})$, and $({\epsilon }_{\mathrm{e}\tau }^{\mathrm{eL}},{\epsilon }_{\mathrm{e}\tau }^{\mathrm{eR}})$ for the nonuniversal and flavor-changing channels, respectively, as well as to the coupling constants for scalar (${\lambda }_0$) and vector (${\lambda }_1$) unparticles to the neutrinos and electrons.

The recently measured semileptonic $D_s$ decay rate can be used to constrain weak annihilation (WA) effects in semileptonic $D$ and $B$ decays. We revisit the theoretical predictions for inclusive semileptonic $D_{(s)}$ decays using a variety of quark mass schemes. The most reliable results are obtained if the fits to $B$ decay distributions are used to eliminate the charm quark mass dependence, without using any specific charm mass scheme. Our fit to the available data shows that WA is smaller than commonly assumed. There is no indication that the WA octet contribution (which is better constrained than the singlet contribution) dominates. The results constrain an important source of uncertainty in the extraction of $|V_{ub}|$ from inclusive semileptonic $B$ decays.

We emphasize that the vanishing of the $CP$ asymmetry in leptogenesis, previously observed for models with tribimaximal mixing and family symmetry, may be traced to a property of the type I seesaw mechanism satisfied by such models known as form dominance, corresponding to the case of a diagonal Casas-Ibarra $R$-matrix. Form dominance leads to vanishing flavor-dependent $CP$ asymmetries irrespective of whether one has tribimaximal mixing or a family symmetry. Successful leptogenesis requires violation of form dominance, but not necessarily violation of tribimaximal mixing. This may be achieved in models where the family symmetry responsible for tribimaximal mixing is implemented indirectly and a strong neutrino mass hierarchy is present with the form dominance broken only softly by the right-handed neutrino responsible for the lightest neutrino mass, as in constrained sequential dominance.

We report an analysis of charmless hadronic decays of neutral $B$ mesons to the final state $K_S^0{K}^{\pm }{\pi }^{\mp }$, using a data sample of $(465\pm 5)\times {10}^6$ $B\overline{B}$ events collected with the BABAR detector at the ${\rm Y}(4S)$ resonance. We observe an excess of signal events with a significance of 5.2 standard deviations including systematic uncertainties and measure the branching fraction to be $\mathcal{B}(B^0\to K_S^0{K}^{\pm }{\pi }^{\mp })=(3.2\pm 0.5\pm 0.3)\times {10}^{-6}$, where the uncertainties are statistical and systematic, respectively.

We study codimension-1 brane solutions of the five-dimensional brane world models compactified on $S_1/{\mathbb{Z}}_2$. In the string theoretical setup, they suggest that the background branes located at orbifold fixed points should be Neveu-Schwarz (NS)-branes (in the five-dimensional sense), rather than D-branes. Indeed, the existence of the background NS-branes is indispensable to obtain flat geometry $M_4\times S_1/{\mathbb{Z}}_2$, where $M_4$ represents the four-dimensional Minkowski spacetime, and without these branes the five-dimensional metric becomes singular everywhere. This result is very reminiscent of the ($p+3$)-dimensional effective string theory [8] where the NS-NS type $p$-brane is indispensable to obtain a flat geometry $R_2$ or $R_2/{\mathbb{Z}}_n$ on the transverse dimensions. Without this NS-NS type $p$-brane, the two-dimensional transverse space becomes a pin-shaped singular space. The correspondence between these two theories leads us to a conjecture that the whole flat backgrounds of the string theory inherently involve the NS-branes implicitly in their ansatz, and hence the true background $p$-branes immanent in our spacetime may be NS-branes, instead of D-branes. We argue that this result can have a significant consequence in the context of the cosmological constant problem.