We study the production and decay of a coupled system of mixed neutral minimal supersymmetric extension of the Standard Model (MSSM) Higgs bosons in exclusive double-diffractive processes at the LHC, including nonvanishing $CP$ phases in the soft supersymmetry-breaking gaugino masses and third-generation trilinear squark couplings. The three neutral Higgs bosons are naturally nearly degenerate, for large values of $\tan \beta$, when the charged Higgs boson weighs around 150 GeV. Large mixing between all three neutral Higgs bosons is possible when $CP$ is violated, a threeway mixing scenario which we also term trimixing. A resolution in the Higgs mass of $\sim 1\mathrm{GeV}$, which may be achievable using the missing-mass method, would allow one to distinguish nearly degenerate Higgs bosons by studying the production lineshape. Measurements of the polarizations of the tau leptons coming from the Higgs-boson decays could offer a direct and observable signal of $CP$ violation in the Higgs sector.

Nonrenormalizable operators both account for the failure of down quark and charged lepton Yukawa couplings to unify and reduce the proton decay rate via dimension-five operators in minimal SUSY SU(5) GUT. We extend the analysis to SUSY SO(10) GUT models.

We obtain reliable $\pi \pi$ scattering amplitudes consistent with experimental data, both at low and high energies, and fulfilling appropriate analyticity properties. We do this by first fitting experimental low energy ($s^{1/2}\le 1.42\mathrm{GeV}$) phase shifts and inelasticities with expressions that incorporate analyticity and unitarity. In particular, for the S wave with isospin 0, we discuss in detail several sets of experimental data. This provides low energy partial wave amplitudes that summarize the known experimental information. Then, we impose Regge behavior as follows from factorization and experimental data for the imaginary parts of the scattering amplitudes at higher energy, and check fulfillment of dispersion relations up to 0.925 GeV. This allows us to improve our fits. The ensuing $\pi \pi$ scattering amplitudes are then shown to verify dispersion relations up to 1.42 GeV, as well as $s-t-u$ crossing sum rules and other consistency conditions. The improved parametrizations therefore provide a reliable representation of pion-pion amplitudes with which one can test chiral perturbation theory calculations, pionium decays, or use as input for $CP$-violating $K$ decays. In this respect, we find $[a_0^{(0)}-a_0^{(2)}{]}^2=(0.077\pm 0.008)M_{\pi }^{-2}$ and ${\delta }_0^{(0)}(m_K^2)-{\delta }_0^{(2)}(m_K^2)=52.9\pm {1.6}^{\mathrm{o}}$.

We study the possibility of brane-world generalization of the Einstein-Straus Swiss-cheese cosmological model. We find that the modifications induced by the brane-world scenario are excessively restrictive. At a first glance only the motion of the boundary is modified and the fluid in the exterior region is allowed to have pressure. The general relativistic Einstein-Straus model emerges in the low density limit. However by imposing that the central mass in the Schwarzschild voids is constant, a combination of the junction conditions and modified cosmological evolution leads to the conclusion that the brane is flat. Thus no generic Swiss-cheese universe can exist on the brane. The conclusion is not altered by the introduction of a cosmological constant in the FLRW regions. This shows that although allowed in the low density limit, the Einstein-Straus universe cannot emerge from cosmological evolution in the brane-world scenario.

We investigate the back reaction of cosmological long wavelength perturbations on the evolution of the Universe. By applying the renormalization group method to a Friedmann-Robertson-Walker universe with long wavelength fluctuations, we demonstrate that the renormalized solution with the back reaction effect is equivalent to that of the separate universe. Then, using the effective Friedmann equation, we show that only the nonadiabatic mode of long wavelength fluctuations affects the expansion law of the spatially averaged universe.

We investigate the scalar field perturbations of the $4+1$-dimensional Schwarzschild black hole immersed in a Gödel universe, described by the Gimon-Hashimoto solution. This may model the influence of the possible rotation of the universe upon the radiative processes near a black hole. In the regime when the scale parameter $j$ of the Gödel background is small, the oscillation frequency is linearly decreasing with $j$, while the damping time is increasing. The quasinormal modes are damping, implying stability of the Schwarzschild-Gödel space-time against scalar field perturbations. The approximate analytical formula for large multipole numbers is found.

We show that the complete static black $p$-brane supergravity solution with a single charge contains two and only two branches with respect to behavior at infinity in the transverse space. One branch is the standard family of asymptotically flat black branes, and another is the family of black branes which asymptotically approach the linear dilaton background (LDB) with antisymmetric form flux. Such configurations were previously obtained in the near-horizon near-extreme limit of the dilatonic asymptotically flat $p$-branes, and used to describe the thermal phase of field theories involved in the domain wall (DW)/quantum field theory (QFT) dualities and the thermodynamics of little string theory in the case of the NS5-brane. Here we show by direct integration of the Einstein equations that the asymptotically LDB $p$-branes are indeed exact supergravity solutions, and we prove a new uniqueness theorem for static $p$-brane solutions satisfying cosmic censorship. In the nondilatonic case, our general nonasymptotically flat $p$-branes are black branes on the background $Ad{S}_{p+2}\times S^{D-p-2}$ supported by the form flux. We develop the general formalism of quasilocal quantities for nonasymptotically flat supergravity solutions with antisymmetric form fields, and show that our solutions satisfy the first law of thermodynamics. We also suggest a constructive procedure to derive rotating asymptotically LDB brane solutions.

The acceleration of the expansion of the universe represents one of the major challenges to our current understanding of fundamental physics. In principle, to explain this phenomenon, at least two different routes may be followed: either adjusting the energy content of the Universe—by introducing a negative-pressure dark energy—or modifying gravity at very large scales—by introducing new spatial dimensions, an idea also required by unification theories. In the cosmological context, the role of such extra dimensions as the source of the dark pressure responsible for the acceleration of our Universe is translated into the so-called brane world (BW) cosmologies. Here we study complementary constraints on a particular class of BW scenarios in which the modification of gravity arises due to a gravitational leakage into extra dimensions. To this end, we use the most recent Chandra measurements of the X-ray gas mass fraction in galaxy clusters, the WMAP determinations of the baryon density parameter, measurements of the Hubble parameter from the HST, and the current supernova data. In agreement with other recent results, it is shown that these models provide a good description for these complementary data, although a closed scenario is always favored in the joint analysis. If we restrict our analysis to the flat case, in accordance with the latest CMB measurements, we found that the so-called “concordance model”, i.e., a flat $\Lambda$CDM universe, provides a slightly better fit to this particular combination of observational data than does a BW model. We, however, emphasize that observational tests of BW scenarios constitute a natural verification of the role of possible extra dimensions in both fundamental physics and cosmology.

This article investigates the signatures of various models of dark energy on weak gravitational lensing, including the complementarity of the linear and nonlinear regimes. It investigates quintessence models and their extension to scalar-tensor gravity. The various effects induced by this simplest extension of general relativity are discussed. It is shown that, given the constraints in the Solar System, models such as a quadratic nonminimal coupling do not leave any signatures that can be detected while other models, such as a runaway dilaton, which include attraction toward general relativity, can let an imprint of about 10%.

In the Randall-Sundrum cosmological models, a $(3+1)$-dimensional brane subject to a $Z_2$ orbifold symmetry is embedded in a $(4+1)$-dimensional bulk spacetime empty except for a negative cosmological constant. The unperturbed braneworld cosmological solutions, subject to homogeneity and isotropy in the three transverse spatial dimensions, are most simply presented by means of a moving brane description. Owing to a generalization of Birkhoff’s theorem, as long as there are no perturbations violating the three-dimensional spatial homogeneity and isotropy, the bulk spacetime remains stationary and trivial. For the spatially flat case, the bulk spacetime is described by one of three bulk solutions: a pure $Ad{S}^5$ solution, an $Ad{S}^5$-Schwarzschild black hole solution, or an $Ad{S}^5$-Schwarzschild naked singularity solution. The brane moves on the boundary of one of these simple bulk spacetimes, its trajectory determined by the evolution of the stress-energy localized on the brane. We derive here the form of the Israel matching conditions for the linearized cosmological perturbations in this moving brane picture. These Israel matching conditions must be satisfied in any gauge. However, they are not sufficient to determine how to describe in a specific gauge the reflection of the bulk gravitational waves off the brane boundary. In this paper we adopt a fully covariant Lorentz gauge condition in the bulk and find the supplementary gauge conditions that must be imposed on the boundary to ensure that the reflected waves do not violate the Lorentz gauge condition. Compared to the form obtained from Gaussian normal coordinates, the form of the Israel matching conditions obtained here is more complex. However, the propagation of the bulk gravitons is simpler because the coordinates used for the background exploit fully the symmetry of the bulk background solution.

The relativistic five-quark equations are found in the framework of the dispersion relation technique. The solutions of these equations using the method based on the extraction of the leading singularities of the amplitudes are obtained. The five-quark amplitudes for the low-lying pentaquarks including the $u$, $d$, $s$ quarks are calculated. The poles of these amplitudes determine the masses of $\theta$ pentaquarks. The mass spectra of the isotensor $\theta$ pentaquarks with $J^P={\frac{1}{2}}^{\pm },{\frac{3}{2}}^{\pm }$ are calculated.

We report about recent results on Dirac wave packets in the treatment of neutrino flavor oscillation where the initial localization of a spinor state implies an interference between positive and negative energy components of mass-eigenstate wave packets. A satisfactory description of fermionic particles requires the use of the Dirac equation as evolution equation for the mass eigenstates. In this context, a new flavor conversion formula can be obtained when the effects of chiral oscillation are taken into account. Our study leads to the conclusion that the fermionic nature of the particles, where chiral oscillations and the interference between positive and negative frequency components of mass-eigenstate wave packets are implicitly assumed, modifies the standard oscillation probability. Nevertheless, for ultrarelativistic particles and sharply peaked momentum distributions, we can analytically demonstrate that these modifications introduce correction factors proportional to $m_{1,2}^2/p_0^2$ which are practically undetectable by any experimental analysis.

In the framework of the large extra-dimensions (LED) model, the effects of LED on the processes $\gamma \gamma \to t\overline{t}{h}^0$ and $e^{+}{e}^{-}\to t\overline{t}{h}^0$ at future linear colliders are investigated in both polarized and unpolarized collision modes. The results show that the virtual Kaluza-Klein graviton exchange can significantly modify the standard model expectations for these processes with certain polarizations of initial states. The process $\gamma \gamma \to t\overline{t}{h}^0$ with $\sqrt{s}=3.5\mathrm{TeV}$ allows the effective scale ${\Lambda }_T$ to be probed up to 7.8 and 8.6 TeV in the unpolarized and $P_{\gamma }=0.9$, $J=2$ polarized $\gamma \gamma$ collision modes, respectively. For the $e^{+}{e}^{-}\to t\overline{t}{h}^0$ process with $\sqrt{s}=3.5\mathrm{TeV}$, the upper limits of ${\Lambda }_T$ to be observed can be 6.7 and 7.0 TeV in the unpolarized and $P_{e^{+}}=0.6$, $P_{e^{-}}=0.8$, $-+$ polarized $e^{+}{e}^{-}$ collision modes, respectively. We find the $\gamma \gamma \to t\overline{t}{h}^0$ channel in $J=2$ polarized photon collision mode provides a possibility to improve the sensitivity to the graviton tower exchange.

We consider the intersection of N different interfaces interpolating between different $Z_N$ vacua of an SU(N) gauge theory using the Polyakov loop order parameter. Topological arguments show that at such a stringlike junction, the order parameter should vanish, implying that the core of this string (i.e. the junction region of all the interfaces) is in the confining phase. Using the effective potential for the Polyakov loop proposed by Pisarski for QCD, we use numerical minimization technique and estimate the energy per unit length of the core of this string to be about $2.7\mathrm{GeV}/\mathrm{fm}$ at a temperature about twice the critical temperature. For the parameters used, the interface tension is obtained to be about $7\mathrm{GeV}/{\mathrm{fm}}^2$. Lattice simulation of pure gauge theories should be able to investigate properties of these strings. For QCD with quarks, it has been discussed in the literature that this $Z_N$ symmetry may still be meaningful, with quark contributions leading to explicit breaking of this $Z_N$ symmetry. With this interpretation, such quark-gluon plasma strings may play important role in the evolution of the quark-gluon plasma phase and in the dynamics of quark-hadron transition.

The complete knowledge of the nucleon spin structure at leading twist requires also addressing the transverse spin distribution of quarks, or transversity, which is yet unexplored because of its chiral-odd nature. Transversity can be best extracted from single-spin asymmetries in fully polarized Drell-Yan processes with antiprotons, where valence contributions are involved anyway. Alternatively, in single-polarized Drell-Yan the transversity happens convoluted with another chiral-odd function, which is likely to be responsible for the well known (and yet unexplained) violation of the Lam-Tung sum rule in the corresponding unpolarized cross section. We present Monte Carlo simulations for the unpolarized and single-polarized Drell-Yan $\overline{p}{p}^{(\uparrow )}\to {\mu }^{+}{\mu }^{-}X$ at different center-of-mass energies in both configurations where the antiproton beam hits a fixed proton target or it collides on another proton beam. The goal is to estimate the minimum number of events needed to extract the above chiral-odd distributions from future measurements at the high energy storage ring (HESR) at GSI. It is important to study the feasibility of such experiments at HESR in order to demonstrate that interesting spin physics can be explored already using unpolarized antiprotons.

We report the continuum limits of the speed of sound, $C_s$, and the specific heat at constant volume, $C_V$, in quenched QCD at temperatures of $2T_c$ and $3T_c$. At these temperatures, $C_s$ is within 2-$\sigma$ of the ideal gas value, whereas $C_V$ differs significantly from the ideal gas. However, both are compatible with results expected in a theory with conformal symmetry. We investigate effective measures of conformal symmetry in the high temperature phase of QCD.

The contributions from the color-octet components $|(c\overline{b}{)}_{\mathbf{8}}({}^{1}S_0)g⟩$ and $|(c\overline{b}{)}_{\mathbf{8}}({}^{3}S_1)g⟩$ to the $h_{B_c}$ or ${\chi }_{B_c}^J$ (the $P$-wave $B_c$ meson) hadroproduction are estimated in terms of the complete $\mathcal{O}({\alpha }_s^4)$ calculation. As necessary inputs in the estimate, we take the values of the octet matrix elements according to the nonrelativistic quantum chromodynamics scaling rules, and as a result, we have found that the contributions to the $P$-wave production may be the same in order of magnitude as those from the color-singlet ones, $|(c\overline{b}{)}_{\mathbf{1}}({}^{1}P_1)⟩$ and $|(c\overline{b}{)}_{\mathbf{1}}({}^{3}P_J)⟩$ ($J=1,2,3$). Especially, our result indicates that the observation of the color-octet contributions to the $P$-wave production in the low transverse momentum region is not very far from the present experimental capability at Tevatron and LHC.

We investigate collective excitations coupled with baryon density in a system of massless three-flavor quarks in the collisionless regime. By using the Nambu–Jona-Lasinio (NJL) model in the mean-field approximation, we field-theoretically derive the spectra both for the normal and color-flavor locked (CFL) superfluid phases at zero temperature. In the normal phase, we obtain usual zero sound as a low-lying collective mode in the particle-hole (vector) channel. In the CFL phase, the nature of collective excitations varies in a way dependent on whether the excitation energy, $\omega$, is larger or smaller than the threshold given by twice the pairing gap $\Delta$, at which pair excitations with nonzero total momentum become allowed to break up into two quasiparticles. For $\omega \ll 2\Delta$, a phonon corresponding to fluctuations in the $\mathrm{U}(1)$ phase of $\Delta$ appears as a sharp peak in the particle-particle (“$H$”) channel. We reproduce the property known from low-energy effective theories that this mode propagates at a velocity of $v_H=1/\sqrt{3}$ in the low momentum regime; the decay constant $f_H$ obtained in the NJL model is identical with the QCD result obtained in the mean-field approximation. We also find that, as the momentum of the phonon increases, the excitation energy goes up and asymptotically approaches $\omega =2\Delta$. Above the threshold for pair excitations ($\omega >2\Delta$), zero sound manifests itself in the vector channel. By locating the zero sound pole of the vector propagator in the complex energy plane, we investigate the attenuation and energy dispersion relation of zero sound. In the long wavelength limit, the phonon mode, the only low-lying excitation, has its spectral weight in the $H$ channel alone, while the spectral function vanishes in the vector channel. This is due to nontrivial mixing between the $H$ and vector channels in the superfluid medium. We finally extend our study to the case of nonzero temperature. We demonstrate how Landau damping smears the phonon peak in the finite temperature spectral function. We find a pure imaginary pole of the $H$ propagator in the complex energy plane, which can be identified as a diffusive mode responsible for the Landau damping. From the pole position we derive the thermal diffusion constant.

We study a neutrino mass texture which can explain the neutrino oscillation data and also saturate the upper bound of the $CP$ asymmetry ${\epsilon }_1$ in the leptogenesis. We consider the thermal and nonthermal leptogenesis based on the right-handed neutrino decay in this model. A lower bound of the reheating temperature required for the explanation of the baryon number asymmetry is estimated as $O({10}^8)\mathrm{GeV}$ for the thermal leptogenesis and $O({10}^6)\mathrm{GeV}$ for the nonthermal one. It can be lower than the upper bound of the reheating temperature imposed by the cosmological gravitino problem. An example of the construction of the discussed texture is also presented.

The vertices $h^{\pm }{W}^{\mp }{h}^0$ and $h^{\pm }{W}^{\mp }{a}^0$, involving the gauge bosons $W^{\mp }$, the lightest charged ($h^{\pm }$), the lightest $CP$-even neutral ($h^0$), and the lightest $CP$-odd neutral ($a^0$) Higgs bosons, arise within the context of many extensions of the standard model, and they can be used to probe the Higgs sector of such extensions via the decays $h^{\pm }\to W^{\pm }{h}^0(a^0)$. We discuss the strength of these vertices for an extension of the minimal supersymmetric standard model with an additional complex Higgs triplet. By using this model, we find regions of the parameter space where the decays $h^{\pm }\to W^{\pm }{h}^0(a^0)$ are not only kinematically allowed, but they also become important decay modes and, in some cases, the dominant ones, with $\mathrm{BR}(h^{\pm }\to W^{\pm }{h}^0)\approx \mathrm{BR}(h^{\pm }\to W^{\pm }{a}^0)$.