We show that certain little Higgs models with symmetry breaking $SU(N)\to SO(N)$ for $N\ge 4$ admit topologically stable solitons that may contribute to cosmological dark matter. We have constructed a spherically symmetric soliton and estimated its mass in the case of $SU(5)\to SO(5)$. Its mass is estimated to be around 10.3 TeV. Whether this particle is a fermion or a boson depends on the value of an integer-valued parameter of the underlying theory, analogous to the number of colors of QCD. In either case, the particle is neutral. If it is a fermion, it is a Majorana particle, which could take part in a seesaw mechanism for neutrino masses.

We present both analytically and numerically a consistent analysis of the dynamics from the Affleck-Dine (AD) mechanism to the subsequent semiclassical evolution in both gravity-mediated and gauge-mediated models. We obtain analytically the elliptic motions in the AD dynamics as the analogy of the well-known Kepler-problem, and by solving the equations of motion on a lattice, we find that the semiclassical evolution goes through three distinct stages as a nonequilibrium process of reheating the Universe: prethermalization, bubble collisions and thermalization. We report that the second stage of our case lasts rather long compared to the second stage of the reheating case, and the thermalization process is unique due to the presence of “thermal $Q$-balls”.

We look into the inner structure of a two-dimensional dilatonic evaporating black hole. We establish and employ the homogenous approximation for the black-hole interior. Two kinds of spacelike singularities are found inside the black hole, and their structure is investigated. We also study the evolution of spacetime from the horizon to the singularity.

We investigate the properties of the FLRW flat cosmological models in which the vacuum energy density evolves with time, $\Lambda (t)$. Using different versions of the $\Lambda (t)$ model, namely, quantum field vacuum, power series vacuum and power law vacuum, we find that the main cosmological functions such as the scale factor of the Universe, the Hubble expansion rate $H$, and the energy densities are defined analytically. Performing a joint likelihood analysis of the recent supernovae type Ia data, the cosmic microwave background shift parameter and the baryonic acoustic oscillations traced by the Sloan Digital Sky Survey galaxies, we put tight constraints on the main cosmological parameters of the $\Lambda (t)$ scenarios. Furthermore, we study the linear matter fluctuation field of the above vacuum models. We find that the patterns of the power series vacuum $\Lambda =n_{1}H+n_2{H}^2$ predict stronger small scale dynamics, which implies a faster growth rate of perturbations with respect to the other two vacuum cases (quantum field and power law), despite the fact that all the cosmological models share the same equation of state parameter. In the case of the quantum field vacuum $\Lambda =n_0+n_2{H}^2$, the corresponding matter fluctuation field resembles that of the traditional $\Lambda$ cosmology. The power law vacuum ($\Lambda \propto a^{-n}$) mimics the classical quintessence cosmology, the best fit being tilted in the phantom phase. In this framework, we compare the observed growth rate of clustering measured from the optical galaxies with those predicted by the current $\Lambda (t)$ models. Performing a Kolmogorov-Smirnov statistical test we show that the cosmological models which contain a constant vacuum ($\Lambda \mathrm{CDM}$), quantum field vacuum, and power law vacuum provide growth rates that match well with the observed growth rate. However, this is not the case for the power series vacuum models (in particular, the frequently adduced $\Lambda \propto H$ model) in which clusters form at significantly earlier times ($z\ge 4$) with respect to all other models ($z\sim 2$). Finally, we derived the theoretically predicted dark matter halo mass function and the corresponding distribution of cluster-size halos for all the models studied. Their expected redshift distribution indicates that it will be difficult to distinguish the closely resembling models (constant vacuum, quantum field, and power law vacuum), using realistic future x-ray surveys of cluster abundances. However, cluster surveys based on the Sunayev-Zeldovich detection method give some hope to distinguish the closely resembling models at high redshifts.

A tiny hypermagnetic field generated before the electroweak phase transition (EWPT) associated to the generation of elementary particle masses can polarize the early Universe hot plasma at huge redshifts $z\gtrsim {10}^{15}$. The anomalous violation of the right-handed electron current characteristic of the EWPT converts the lepton asymmetry into a baryon asymmetry. Under reasonable approximations, the magnetic field strength inferred by requiring such “leptogenic” origin for the observed baryon asymmetry of the Universe matches the large-scale cosmological magnetic field strengths estimated from current astronomical observations.

The relic gravitational waves are the cleanest probe of the violent times in the very early history of the Universe. They are expected to leave signatures in the observed cosmic microwave background anisotropies. We significantly improved our previous analysis [W. Zhao, D. Baskaran, and L. P. Grishchuk, Phys. Rev. D 79, 023002 (2009)] of the 5-year WMAP $TT$ and $TE$ data at lower multipoles $\ell$. This more general analysis returned essentially the same maximum likelihood result (unfortunately, surrounded by large remaining uncertainties): The relic gravitational waves are present and they are responsible for approximately 20% of the temperature quadrupole. We identify and discuss the reasons by which the contribution of gravitational waves can be overlooked in a data analysis. One of the reasons is a misleading reliance on data from very high multipoles $\ell$ and another a too narrow understanding of the problem as the search for $B$ modes of polarization, rather than the detection of relic gravitational waves with the help of all correlation functions. Our analysis of WMAP5 data has led to the identification of a whole family of models characterized by relatively high values of the likelihood function. Using the Fisher matrix formalism we formulated forecasts for Planck mission in the context of this family of models. We explore in detail various “optimistic,” “pessimistic,” and “dream case” scenarios. We show that in some circumstances the $B$-mode detection may be very inconclusive, at the level of signal-to-noise ratio $S/N=1.75$, whereas a smarter data analysis can reveal the same gravitational wave signal at $S/N=6.48$. The final result is encouraging. Even under unfavorable conditions in terms of instrumental noises and foregrounds, the relic gravitational waves, if they are characterized by the maximum likelihood parameters that we found from WMAP5 data, will be detected by Planck at the level $S/N=3.65$.

We present an extension of the minimal supersymmetric standard model where the dominant decay channel of the Higgs boson is a cascade decay into a four-gluon final state. In this model the Higgs is a pseudo-Goldstone boson of a broken global symmetry $SU(3)\to SU(2)$. Both the global symmetry breaking and electroweak symmetry breaking are radiatively induced. The global symmetry breaking pattern also implies the existence of a light (few GeV) pseudo-Goldstone boson $\eta$ which is a singlet under the standard model gauge group. The $h\to \eta \eta$ branching fraction is large, and typically dominates over the standard $h\to bb$ decay. The dominant decay of $\eta$ is into two gluons, while the decays to photons, taus or lighter standard model flavors are suppressed at the level of ${10}^{-4}$ or more. With $h\to 4\mathrm{\text{jets}}$ as the dominant decay, the Higgs could be as light as 78 GeV without being detected at LEP, while detection at the LHC is extremely challenging. However many of the super- and global symmetry partners of the standard model particles should be easily observable at the LHC. Furthermore, the LHC should be able to observe a “wrong” Higgs that is a 300–400 GeV heavy Higgs-like particle with suppressed couplings to $W$ and $Z$ that by itself does not account for electroweak precision observables and the unitarity of $WW$ scattering. At the same time, the true Higgs is deeply buried in the QCD background.

A description of fragmentation functions which satisfy the momentum and isospin sum rules is presented in an effective quark theory. Concentrating on the pion fragmentation function, we first explain why the elementary (lowest order) fragmentation process $q\to q\pi$ is completely inadequate to describe the empirical data, although the crossed process $\pi \to q\overline{q}$ describes the quark distribution functions in the pion reasonably well. Taking into account cascadelike processes in a generalized jet-model approach, we then show that the momentum and isospin sum rules can be satisfied naturally, without the introduction of ad hoc parameters. We present results for the Nambu–Jona-Lasinio (NJL) model in the invariant mass regularization scheme and compare them with the empirical parametrizations. We argue that the NJL-jet model, developed herein, provides a useful framework with which to calculate the fragmentation functions in an effective chiral quark theory.

This paper examines sterile neutrino oscillation models in light of recently published results from the MiniBooNE Experiment. The new MiniBooNE data include the updated neutrino results, including the low-energy region, and the first antineutrino results, as well as first results from the off-axis NuMI beam observed in the MiniBooNE detector. These new global fits also include data from LSND, KARMEN, NOMAD, Bugey, CHOOZ, CCFR84, and CDHS. Constraints from atmospheric oscillation data have been imposed. We test the validity of the three-active plus one-sterile ($3+1$) and two-sterile ($3+2$) oscillation hypotheses, and we estimate the allowed range of fundamental neutrino oscillation parameters in each case. We assume $CPT$-invariance throughout. However, in the case of ($3+2$) oscillations, $CP$ violation is allowed. We find that, with the addition of the new MiniBooNE data sets, a ($3+2$) oscillation hypothesis provides only a marginally better description of all short-baseline data over a ($3+1$) oscillation hypothesis. In the case of ($3+2$) $CP$-violating models, we obtain good ${\chi }^2$-probabilities in general due to the large number of fit parameters. However, we find large incompatibilities among appearance and disappearance experiments, consistent with previous analyses. Aside from LSND, the data sets responsible for this tension are the MiniBooNE neutrino data set, CDHS, and the atmospheric constraints. In addition, new incompatibilities are found between the appearance experiments themselves (MiniBooNE, LSND, KARMEN and NOMAD), independent of $CP$-violation assumptions. On the other hand, fits to antineutrino-only data sets, including appearance and disappearance experiments, are found significantly more compatible, even within a ($3+1$) oscillation scenario.

In this paper we study the function $\chi (x_1,x_2,g)$ that determines the dressing phase that appears in the all-loop Bethe ansatz equations for the $SL(2)$ sector of $\mathcal{N}=4$ super Yang-Mills theory. First, we consider the coefficients $c_{r,s}(g)$ of the expansion of $\chi (x_1,x_2,g)$ in inverse powers of $x_{1,2}$. We obtain an expression in terms of a single integral valid for all values of the coupling $g$. The expression is such that the small and large coupling expansion can be simply computed in agreement with the expected results. This proves the, up to now conjectured, equivalence of both expansions of the phase. The strong coupling expansion is only asymptotic but we find an exact expression for the value of the residue which can be seen to decrease exponentially with $g$. After that, we consider the function $\chi (x_1,x_2,g)$ itself and, using the same method, expand it for small and large coupling. All small and large coupling coefficients ${\chi }^{(n)}(x_1,x_2)$, for even and odd $n$, are explicitly given in terms of finite sums or, alternatively, in terms of the residues of generating functions at certain poles.

The relativistic spinning particle model, proposed in [S. M. Kuzenko, S. L. Lyakhovich, and A. Y. Segal, Int. J. Mod. Phys. A 10, 1529 (1995); A. Staruszkiewicz, Acta Phys. Pol. A 1, 109 (2008).] is analyzed in a Hamiltonian framework. The spin is simulated by extending the configuration space by introducing a lightlike four vector degree of freedom. The model is heavily constrained and constraint analysis, in the Dirac scheme, is both novel and instructive. Our major finding is an associated novel noncommutative structure in the extended space. This is obtained in a particular gauge. The model possesses a large gauge freedom and hence a judicious choice of gauge becomes imperative. The gauge fixed system in reduced phase space simplifies considerably for further study. We have shown that this noncommutative phase space algebra is essential in revealing the spin effects in the particle model through the Lorentz generator and Hamiltonian equations of motion.

We study the evolution of a perfect-fluid sphere coupled to a scalar radiation field. By ensuring a Ricci invariant regularity as a conformally flat spacetime at the central world line we find that the fluid coupled to the scalar field satisfies the equation of state ${\rho }_c+3p_c=\mathrm{\text{const}}$ at the center of the sphere, where the energy ${\rho }_c$ density and the pressure $p_c$ do not necessarily contain the scalar field contribution. The fluid can be interpreted as anisotropic and radiant because of the scalar field, but it becomes perfect and nonradiative at the center of the sphere. These results are currently being considered to build up a numerical relativistic hydrodynamic solver.

We use the combinatorial and number-theoretical methods developed in previous works by the authors to study black hole entropy in the new proposal put forth by Engle, Noui, and Pérez. Specifically, we give the generating functions relevant for the computation of the entropy and use them to derive its asymptotic behavior, including the value of the Immirzi parameter and the coefficient of the logarithmic correction.

It is shown in this paper that minisuperspace quantization of homogeneous and isotropic geometries with phantom scalar fields, when examined in the light of the Bohm-de Broglie interpretation of quantum mechanics, does not eliminate, in general, the classical big rip singularity present in the classical model. For some values of the Hamilton-Jacobi separation constant present in a class of quantum state solutions of the Wheeler-De Witt equation, the big rip can be either completely eliminated or may still constitute a future attractor for all expanding solutions. This is contrary to the conclusion presented in [M. P. Dabrowski, C. Kiefer, and B. Sandhofer, Phys. Rev. D 74, 044022 (2006).], using a different interpretation of the wave function, where the big rip singularity is completely eliminated (“smoothed out”) through quantization, independently of such a separation constant and for all members of the above mentioned class of solutions. This is an example of the very peculiar situation where different interpretations of the same quantum state of a system are predicting different physical facts, instead of just giving different descriptions of the same observable facts: in fact, there is nothing more observable than the fate of the whole Universe.

In this paper the collision of two cosmic string loops is studied. After collision junctions are formed and the loops are entangled. We show that after their formation the junctions start to unzip and the loops disentangle. This analysis provides a theoretical understanding of the unzipping effect observed in numerical simulations of a network of cosmic strings with more than one type of cosmic strings. The unzipping phenomena have important effects in the evolution of cosmic string networks when junctions are formed upon collision, such as in a network of cosmic superstrings.

If the hemispherical power asymmetry observed in the cosmic microwave background (CMB) on large angular scales is attributable to a superhorizon curvaton fluctuation, then the simplest model predicts that the primordial density fluctuations should be similarly asymmetric on all smaller scales. The distribution of high-redshift quasars was recently used to constrain the power asymmetry on scales $k\simeq 1.5h{\mathrm{Mpc}}^{-1}$, and the upper bound on the amplitude of the asymmetry was found to be a factor of 6 smaller than the amplitude of the asymmetry in the CMB. We show that it is not possible to generate an asymmetry with this scale dependence by changing the relative contributions of the inflaton and curvaton to the adiabatic power spectrum. Instead, we consider curvaton scenarios in which the curvaton decays after dark matter freezes out, thus generating isocurvature perturbations. If there is a superhorizon fluctuation in the curvaton field, then the rms amplitude of these perturbations will be asymmetric, and the asymmetry will be most apparent on large angular scales in the CMB. We find that it is only possible to generate the observed asymmetry in the CMB while satisfying the quasar constraint if the curvaton’s contribution to the total dark matter density is small, but nonzero. The model also requires that the majority of the primordial power comes from fluctuations in the inflaton field. Future observations and analyses of the CMB will test this model because the power asymmetry generated by this model has a specific spectrum, and the model requires that the current upper bounds on isocurvature power are nearly saturated.

Models of dark energy in which neutrinos interact with the scalar field supposed to be responsible for the acceleration of the Universe usually imply a variation of the neutrino masses on cosmological time scales. In this work we propose a parametrization for the neutrino mass variation that captures the essentials of those scenarios and allows one to constrain them in a model independent way, that is, without resorting to any particular scalar field model. Using WMAP 5 yr data combined with the matter power spectrum of SDSS and 2dFGRS, the limit on the present value of the neutrino mass is $m_0\equiv m_{\nu }(z=0)<0.43$ (0.28) eV at 95% C.L. for the case in which the neutrino mass was lighter (heavier) in the past, a result competitive with the ones imposed for standard (i.e., constant mass) neutrinos. Moreover, for the ratio of the mass variation of the neutrino mass $\Delta m_{\nu }$ over the current mass $m_0$ we found that $\log [|\Delta m_{\nu }|/m_0]<-1.3$ ($-2.7$) at 95% C.L. for $\Delta m_{\nu }<0$ ($\Delta m_{\nu }>0$), totally consistent with no mass variation. These stringent bounds on the mass variation are not related to the neutrino freestreaming history which may affect the matter power spectrum on small scales. On the contrary, they are imposed by the fact that any significant transfer of energy between the neutrino and dark energy components would lead to an instability contradicting CMB and large-scale structure data on the largest observable scales.

We study the effects of gravitational lensing on the estimation of non-Gaussianity from the bispectrum of the CMB temperature anisotropies. We find that the effect of lensing on the bispectrum may qualitatively be described as a smoothing of the acoustic features analogous to the temperature power spectrum. In contrast to previous results, for a Planck-like experiment which is cosmic-variance limited to ${\ell }_{\max }=2000$, we find that lensing causes no significant degradation of our ability to constrain the non-Gaussianity amplitude $f_{\mathrm{NL}}$ for both local and equilateral configurations, provided that the biases due to the cross correlation between the lensing potential and the integrated-Sachs-Wolfe contribution to the CMB temperature are adequately understood. With numerical simulations, we also verify that low-order Taylor approximations to the lensed bispectrum and integrated-Sachs-Wolfe-lensing biases are accurate.