We propose an efficient method for generating high accuracy ($\sim 1\%$) nonlinear power spectra for grids of dark energy cosmologies. Our prescription for matching matter growth automatically matches the main features of the cosmic microwave background (CMB) anisotropy power spectrum, thus naturally including “CMB priors.”

We suggest that the newly observed resonance $Y(4260)$ is a ${\chi }_c-{\rho }^0$ molecule, which is an isovector. In this picture, we can easily interpret why $Y(4260)\to {\pi }^{+}{\pi }^{-}J/\psi$ has a larger rate than $Y(4260)\to D\overline{D}$ which has not been observed, and we also predict existence of the other two components of the isotriplet and another two possible partner states which may be observed in the future experiments. A direct consequence of this structure is that for this molecular structure $Y(4260)\to {\pi }^{+}{\pi }^{-}J/\psi$ mode is more favorable than $Y(4260)\to K\overline{K}J/\psi$ which may have a larger fraction if other proposed structures prevail.

If the $X(3872)$ is a loosely bound molecule of the charm mesons $D^0{\overline{D}}^{*0}$ and $D^{*0}{\overline{D}}^0$, it can decay through the decay of a constituent in a hadronic channel with a nearby threshold, such as $J/\psi \omega$ or $J/\psi \rho$. The differential decay rates of the $X$ into $J/\psi {\pi }^{+}{\pi }^{-}$, $J/\psi {\pi }^{+}{\pi }^{-}{\pi }^0$, $J/\psi {\pi }^0\gamma$, and $J/\psi \gamma$ are calculated in terms of $XJ/\psi \rho$ and $XJ/\psi \omega$ coupling constants using an effective Lagrangian that reproduces the decay rates of the $\omega$ and the $\rho$. The dependence of the coupling constants on the binding energy and the total width of the $X$ is determined by a factorization formula. Results from a model by Swanson are used to predict the partial width of $X$ into $J/\psi {\pi }^{+}{\pi }^{-}{\pi }^0$ as a function of the binding energy and the total width of the $X$.

Considering the density dependence of quark masses, we investigate the color-flavor-locked matter and its stability relative to (unpaired) strange quark matter. We find that, when the current mass of strange quark $m_s$ is small, the strange quark matter remains stable for moderate baryon densities. When $m_s$ is large, the gapless phase of the color-flavor-locked matter is found to be difficult to be stable. A schematic phase diagram of three-flavor quark matter is presented, in which the color-flavor-locked phase region is suppressed in comparison with the previous results.

We derive a geometric representation of couplings between spin degrees of freedom and gauge fields within the worldline approach to quantum field theory. We combine the string-inspired methods of the worldline formalism with elements of the loop-space approach to gauge theory. In particular, we employ the loop (or area) derivative operator on the space of all holonomies which can immediately be applied to the worldline representation of the effective action. This results in a spin factor that associates the information about spin with zigzag motion of the fluctuating field. Concentrating on the case of quantum electrodynamics in external fields, we obtain a purely geometric representation of the Pauli term. To one-loop order, we confirm our formalism by rederiving the Heisenberg-Euler effective action. Furthermore, we give closed-form worldline representations for the all-loop order effective action to lowest nontrivial order in a small-$N_{\mathrm{f}}$ expansion.

We study post weak decoupling coherent active-sterile and active-active matter-enhanced neutrino flavor transformation in the early Universe. We show that flavor conversion efficiency at Mikheyev-Smirnov-Wolfenstein resonances is likely to be high (adiabatic evolution) for relevant neutrino parameters and energies. However, we point out that these resonances cannot sweep smoothly and continuously with the expansion of the Universe. We show how neutrino flavor conversion in this way can leave both the active and sterile neutrinos with nonthermal energy spectra, and how, in turn, these distorted energy spectra can affect the neutron-to-proton ratio, primordial nucleosynthesis, and cosmological mass/closure constraints on sterile neutrinos. We demonstrate that the existence of a light sterile neutrino which mixes with active neutrinos can change fundamentally the relationship between the cosmological lepton numbers and the primordial nucleosynthesis ${}^4\mathrm{He}$ yield.

We define the cohomogeneity one string, string with continuous symmetries, as its world surface is tangent to a Killing vector field of a target space. We classify the Killing vector fields by an equivalence relation using isometries of the target space. We find that the equivalence classes of Killing vectors in Minkowski spacetime are partitioned into seven families. It is clarified that there exist seven types of strings with spacelike symmetries and four types of strings with timelike symmetries, stationary strings.

In this paper we discuss how to extract information about physics beyond the standard model (SM) from searches for a light SM Higgs boson at Tevatron Run II and CERN LHC. We demonstrate that new (pseudo)scalar states predicted in both supersymmetric and dynamical models can have enhanced visibility in standard Higgs search channels, making them potentially discoverable at Tevatron Run II and CERN LHC. We discuss the likely sizes of the enhancements in the various search channels for each model and identify the model features having the largest influence on the degree of enhancement. We compare the key signals for the nonstandard scalars across models and also with expectations in the SM, to show how one could start to identify which state has actually been found. In particular, we suggest the likely mass reach of the Higgs search in $p\overline{p}/pp\to \mathcal{H}\to {\tau }^{+}{\tau }^{-}$ for each kind of nonstandard scalar state and we demonstrate that $p\overline{p}/pp\to \mathcal{H}\to \gamma \gamma$ may cleanly distinguish the scalars of supersymmetric models from those of dynamical models.

Rotation angle of the plane of polarization of the distant galactic radio waves has been estimated in a string inspired axion-dilaton background. It is found that the axion, dual to the field strength of the second rank massless antisymmetric Kalb-Ramond field in the string spectrum, produces a wavelength-independent optical rotation which is much larger than that produced by the dilaton. Detection of such rotation has been reported in some recent cosmological experiments. The observed value has been compared with our estimated theoretical value following various cosmological constraints. The effects of warped extra dimensions in a braneworld scenario on such an optical rotation have been investigated.

It is widely believed that the top loop corrections to the Higgs effective potential destabilize the electroweak vacuum and that, imposing stability, lower bounds on the Higgs mass can be derived. With the help of a scalar-Yukawa model, we show that this apparent instability is due to the extrapolation of the potential into a region where it is no longer valid. Stability turns out to be an intrinsic property of the theory (rather than an additional constraint to be imposed on it). However, lower bounds for the Higgs mass can still be derived with the help of a criterion dictated by the properties of the potential itself. If the scale of new physics lies in the TeV region, sizable differences with the usual bounds are found. Finally, our results exclude the alternative metastability scenario, according to which we might be living in a sufficiently long lived metastable electroweak vacuum.

Generalizations of gravitational Born-Infeld type Lagrangians are investigated. Phenomenological constraints (reduction to Einstein-Hilbert action for small curvature, spin-two ghost freedom, and absence of Coulomb-like Schwarschild singularity) select one effective Lagrangian whose dynamics is dictated by the tensors $g_{\mu \nu }$ and ${\mathcal{R}}_{\mu \nu \rho \sigma }$ (not $R_{\mu \nu }$ or the scalar $R$).

The effects of an extra $Z^{\prime }$ gauge boson with family nonuniversal fermion couplings on the rare top quark decay $t\to c\gamma$ are first examined in a model-independent way and then in the minimal 331 model. It is found that the respective branching fraction is at most of the order of ${10}^{-8}$ for $m_{Z^{\prime }}=500$ GeV and dramatically decreases for a heavier $Z^{\prime }$ boson. This results is in sharp contrast with a previous evaluation of this decay in the context of topcolor-assisted technicolor models, which found that $B(t\to c\gamma )\simeq {10}^{-6}$ for $m_{Z^{\prime }}=1$ TeV.

We investigate the role of $CP$ phases within the renormalizable SUSY $SO(10)$ GUT with one ${10}_H$, one ${\overline{126}}_H$ one ${126}_H$ and one ${210}_H$ Higgs representations and type II seesaw dominating the neutrino mass matrix. This framework is non trivially predictive in the fermionic sector and connects in a natural way the GUT unification of $b$ and $\tau$ Yukawa couplings with the bi-large mixing scenario for neutrinos. On the other hand, existing numerical analysis claim that consistency with quark and charged lepton data prevents the minimal setup from reproducing the observed $CP$ violation via the Cabibbo-Kobayashi-Maskawa (CKM) matrix. We re-examine the issue and find by inspection of the fermion mass sum rules and a detailed numerical scan that, even though the CKM phase preferentially takes values in the second quadrant, the agreement of the minimal model with the data is actually obtained in a non negligible fraction of the parameter space. We then consider a recently proposed renormalizable extension of the minimal model, obtained by adding one chiral 120-dimensional Higgs supermultiplet. We show that within such a setup the CKM phase falls naturally in the observed range. We emphasize the robust predictivity of both models here considered for neutrino parameters that are in the reach of ongoing and future experiments.

We report the observation of $B^{-}\to J/\psi \Lambda \overline{p}$ and searches for $B^{-}\to J/\psi {\Sigma }^0\overline{p}$ and $B^0\to J/\psi p\overline{p}$ decays, using a sample of $275\times {10}^6$ $B\overline{B}$ pairs collected with the Belle detector at the ${\rm Y}(4S)$ resonance. We observe a signal of $17.2\pm 4.1$ events with a significance of $11.1\sigma$ and obtain a branching fraction of $\mathcal{B}(B^{-}\to J/\psi \Lambda \overline{p})=11.6\pm 2.8(\mathrm{stat}{)}_{-2.3}^{+1.8}(\mathrm{sys})\times {10}^{-6}$. No signal is found for either of the two decay modes, $B^{-}\to J/\psi {\Sigma }^0\overline{p}$ and $B^0\to J/\psi p\overline{p}$, and upper limits for the branching fractions are determined to be $\mathcal{B}(B^{-}\to J/\psi {\Sigma }^0\overline{p})<1.1\times {10}^{-5}$ and $\mathcal{B}(B^0\to J/\psi p\overline{p})<8.3\times {10}^{-7}$ at 90% confidence level.

We explore a possibility for the Universe to cross the $w=-1$ cosmological constant barrier for the dark energy state parameter. We consider the Universe as a slowly decaying D3-brane. The D3-brane dynamics are approximately described by a nonlocal string tachyon interaction and the backreaction of gravity is incorporated in the closed string tachyon dynamics. In a local effective approximation this model contains one phantom component and one usual field with a simple polynomial interaction. To understand cosmological properties of this system we study toy models with the same scalar fields but with modified interactions. These modifications admit polynomial superpotentials. We find restrictions on these interactions under which it is possible to reach $w=-1$ from below at large time. Explicit solutions with the dark energy state parameter crossing or not crossing the barrier $w=-1$ at large time are presented.

Using quadratic spinor techniques we demonstrate that the Immirzi parameter can be expressed as ratio between scalar and pseudoscalar contributions in the theory and can be interpreted as a measure of how Einstein gravity differs from a generally constructed covariant theory for gravity. This interpretation is independent of how gravity is quantized. One of the important advantage of deriving the Immirzi parameter using the quadratic spinor techniques is to allow the introduction of renormalization scale associated with the Immirzi parameter through the expectation value of the spinor field upon quantization.

We present the concomitant decomposition of an $(s+2)$-dimensional space-time both with respect to a timelike and a spacelike direction. The formalism we develop is suited for the study of the initial value problem and for canonical gravitational dynamics in braneworld scenarios. The bulk metric is replaced by two sets of variables. The first set consists of one tensorial (the induced metric $g_{ij}$), one vectorial ($M^i$) and one scalar ($M$) dynamical quantity, all defined on the $s$ space. Their time evolutions are related to the second fundamental form (the extrinsic curvature $K_{ij}$), the normal fundamental form (${\mathcal{K}}^i$) and normal fundamental scalar ($\mathcal{K}$), respectively. The nondynamical set of variables is given by the lapse function and the shift vector, which however has one component less. The missing component is due to the externally imposed constraint, which states that physical trajectories are confined to the $(s+1)$-dimensional brane. The pair of dynamical variables ($g_{ij}$, $K_{ij}$), well known from the Arnowitt-Deser-Misner decomposition is supplemented by the pairs ($M^i$, ${\mathcal{K}}^i$) and ($M$, $\mathcal{K}$) due to the bulk curvature. We give all projections of the junction condition across the brane and prove that for a perfect fluid brane neither of the dynamical variables has jump across the brane. Finally we complete the set of equations needed for gravitational dynamics by deriving the evolution equations of $K_{ij}$, ${\mathcal{K}}^i$ and $\mathcal{K}$ on a brane with arbitrary matter.

We study the one-loop contributions of the effective flavor changing neutral couplings (FCNC) $tcZ$, $tcH$, and $tc\gamma$ on the electroweak precision observables ${\Gamma }_Z,R_c,R_b,R_{\ell },A_c$, and $A_c^{FB}$, as well as the oblique parameters $S$ and $T$. Using the known experimental limits on these observables, we may place 95% C.L. bounds on these FCNC couplings which in turn translate into the following limits for the branching ratios $\mathrm{BR}(t\to cZ)\le 1.6\times {10}^{-2}$ and $\mathrm{BR}(t\to cH)\le (0.09-2.8)\times {10}^{-3}$ for $114\le m_H\le 170\mathrm{GeV}$.