Assuming a minimal seesaw model with two heavy neutrinos ($N$), we examine effects of leptonic $CP$ violation induced by approximate $\mu$-$\tau$ symmetric interactions. As long as $N$ is subject to the $\mu$-$\tau$ symmetry, we can choose $CP$ phases of Dirac mass terms without loss of generality in such a way that these phases arise from $\mu$-$\tau$ symmetry breaking interactions. In the case that no phase is present in heavy neutrino mass terms, leptonic $CP$ phases are controlled by two phases $\alpha$ and $\beta$. The similar consideration is extended to $N$ blind to the $\mu$-$\tau$ symmetry. It is argued that $N$ subject (blind) to the $\mu$-$\tau$ symmetry necessarily describes the normal (inverted) mass hierarchy. We restrict ourselves to $\mu$-$\tau$ symmetric textures giving the tribimaximal mixing and calculate flavor neutrino masses to estimate $CP$-violating Dirac and Majorana phases as well as neutrino mixing angles as functions of $\alpha$ and $\beta$. Since $\alpha$ and $\beta$ are generated by $\mu$-$\tau$ symmetry breaking interactions, the $CP$-violating Majorana phase tends to be suppressed and is found to be at most $\mathcal{O}(0.1)$ radian. On the other hand, the $CP$-violating Dirac phase tends to show a proportionality to $\alpha$ or to $\beta$.

The mass shifts of the $P$-wave $D_s$ and $B_s$ mesons due to coupling to $DK$, $D^{*}K$ and $BK$, $B^{*}K$ channels are studied using the chiral quark-pion Lagrangian not containing fitting parameters. The large mass shifts down $\sim 140\mathrm{MeV}$ and $\sim 100\mathrm{MeV}$ for $D_s^{*}(0^{+})$ and $D_s(1^{{+}^{\prime }})$ and $\sim 100\mathrm{MeV}$ for $B_s^{*}(0^{+})$ and $B_s(1^{{+}^{\prime }})$ are calculated. Two factors are essential for large mass shifts: strong coupling of the $0^{+}$ and $1^{{+}^{\prime }}$ states to the $S$-wave decay channel, containing a Nambu-Goldstone meson, and the chiral flip transitions due to the bispinor structure of both heavy-light mesons. The masses $M(B_s^{*}(0^{+}))=5710(15)\mathrm{MeV}$ and $M(B_s(1^{{+}^{\prime }}))=5730(15)\mathrm{MeV}$, very close to $M(B(0^{+}))$ and $M(B(1^{{+}^{\prime }}))$, are predicted. The experimental limit on the width $\Gamma (D_{s1}(2536))<2.3\mathrm{MeV}$ puts strong restrictions on the admissible mixing angle between the $1^{+}$ and $1^{{+}^{\prime }}$ states, $|\varphi |<6°$, which corresponds to the mixing angle $\theta$ between the ${}^{3}P_1$ and ${}^{1}P_1$ states, $29°<\theta <41°$.

It has been shown that tribimaximal mixing can be obtained by some particular breaking pattern of the $A_4$ symmetry, wherein the extra $A_4$ triplet Higgs scalars pick up certain fixed vacuum expectation value (VEV) alignments. We have performed a detailed analysis of the different possible neutrino mass matrices within the framework of the $A_4$ model. We take into account all possible singlet and triplet Higgs scalars which leave the Lagrangian invariant under $A_4$. We break $A_4$ spontaneously, allowing the Higgs to take any VEV in general. We show that the neutrino mixing matrix deviates from tribimaximal, both due to the presence of the extra Higgs singlets, as well as from the deviation of the triplet Higgs VEV from its desired alignment, taken previously. We solve the eigenvalue problem for a variety of these illustrative cases and identify the ones where one obtains exact tribimaximal mixing. All such cases require fine-tuning. We show which neutrino mass matrices would be strongly disfavored by the current neutrino data. Finally, we study in detail the phenomenology of the remaining viable mass matrices and establish the deviation of the neutrino mixing from tribimaximal, both analytically as well as numerically.

The Kamioka-Korea two-detector system is a powerful experimental setup for resolving neutrino parameter degeneracies and probing $CP$ violation in neutrino oscillation. In this paper, we study sensitivities of the same setup to several nonstandard neutrino physics such as quantum decoherence, tiny violation of Lorentz symmetry, and nonstandard interactions of neutrinos with matter. We show that it can achieve significant improvement on the current bounds on nonstandard neutrino physics. In most cases, the Kamioka-Korea two-detector setup is more sensitive than the one-detector setup, either in Kamioka or in Korea, except for the cases when Lorentz symmetry is broken in a CPT-violating manner and the nonstandard neutrino interactions with matter is present.

We compare a recently derived, resummed high post-Newtonian accuracy effective-one-body (EOB) quadrupolar waveform to the results of a numerical simulation of the inspiral and merger of an equal-mass black-hole binary. We find a remarkable agreement, both in phase and in amplitude, with a maximal dephasing which can be reduced below $\pm 0.005$ gravitational-wave cycles over 12 gravitational-wave cycles corresponding to the end of the inspiral, the plunge, the merger, and the beginning of the ring-down. This level of agreement is shown for two different values of the effective fourth post-Newtonian parameter $a_5$, and for corresponding, appropriately flexed values of the radiation-reaction resummation parameter $v_{\mathrm{pole}}$. In addition, our resummed-EOB amplitude agrees to better than the 1% level with the numerical-relativity one up to the late inspiral. These results, together with other recent work on the EOB-numerical-relativity comparison, confirm the ability of the EOB formalism to accurately capture the general-relativistic waveforms.

The purported observation of a state ${\Theta }^{+}$ with strangeness $S=+1$ led to its quark model interpretation in terms of a pentaquark combination involving a triquark-diquark structure—the Karliner-Lipkin model. In this work, the proper color-spin symmetry properties for the $qq\overline{q}$ triquark are elucidated by calculating the SU(6) unitary scalar factors and Racah coefficients. Using these results, the color-spin hyperfine interactions, including flavor symmetry breaking therein, become straightforward to incorporate and the pentaquark masses are readily obtained. We examine the effect on the pentaquark mass of (a) deviations from the flavor symmetric limit and (b) different strengths of the doublet and triplet hyperfine interactions. Reference values of these parameters yield a ${\Theta }^{+}$ mass prediction of 1601 MeV but it can comfortably accommodate 1540 MeV for alternate choices. In the same framework, other pentaquark states $\Xi (S=-2)$ and ${\Theta }^c$ (with charm $C=-1$) are expected at 1783 MeV and 2757 MeV, respectively.

We use a functional approach to the Casimir effect in order to evaluate the exact vacuum energy for a real scalar field in $d+1$ dimensions, in the presence of backgrounds that, in a particular limit, impose Dirichlet boundary conditions on one or two parallel surfaces. Outside of that limit, the backgrounds are described by a nonlocal effective action and may be thought of as modelling finite-width mirrors with frequency-dependent transmission and reflection coefficients. We obtain formal expressions for the Casimir energy in general backgrounds, and provide new explicit results in some particular cases.

We perform a detailed investigation of the simplest possible cosmological model in which a bounce can occur, namely, that where the dynamics is led by a simple massive scalar field in a general self-interacting potential and a background spacetime with positively curved spatial sections. By means of a phase space analysis, we give the conditions under which an initially contracting phase can be followed by a bounce and an inflationary phase lasting long enough (i.e., at least 60–70 e-folds) to suppress spatial curvature in today’s observable universe. We find that, quite generically, this realization requires some amount of fine-tuning of the initial conditions. We study the effect of this background evolution on scalar perturbations by propagating an initial power-law power spectrum through the contracting phase, the bounce, and the inflationary phase. We find that it is drastically modified, both spectrally ($k$-mode mixing) and in amplitude. It also acquires, at leading order, an oscillatory component, which, once evolved through the radiation and matter dominated eras, happens to be compatible with observational data.

We solve for the behavior of cosmological perturbations in the Dvali-Gabadadze-Porrati (DGP) braneworld model using a new numerical method. Unlike some other approaches in the literature, our method uses no approximations other than linear theory and is valid on large scales. We examine the behavior of late-universe density perturbations for both the self-accelerating and normal branches of DGP cosmology. Our numerical results can form the basis of a detailed comparison between the DGP model and cosmological observations.

We give a concise formula for the non-Gaussianity of the primordial curvature perturbation generated on superhorizon scales in the multiscalar inflation model without assuming slow-roll conditions. This is an extension of our previous work. Using this formula, we study the generation of non-Gaussianity for the double inflation models in which the slow-roll conditions are temporarily violated after horizon exit, and we show that the nonlinear parameter $f_{\mathrm{NL}}$ for such models is suppressed by the slow-roll parameters evaluated at the time of horizon exit.

Surface effects in strange-quark matter play an important role for certain observables which have been proposed in order to identify strange stars, and color superconductivity can strongly modify these effects. We study the surface of color superconducting strange-quark matter by solving the Hartree-Fock-Bogoliubov equations for finite systems (“strangelets”) within the MIT bag model, supplemented with a pairing interaction. Because of the bag-model boundary condition, the strange-quark density is suppressed at the surface. This leads to a positive surface charge, concentrated in a layer of $\sim 1\mathrm{fm}$ below the surface, even in the color-flavor locked (CFL) phase. However, since in the CFL phase all quarks are paired, this positive charge is compensated by a negative charge, which turns out to be situated in a layer of a few tens of fm below the surface, and the total charge of CFL strangelets is zero. We also study the surface and curvature contributions to the total energy. Because of the strong pairing, the energy as a function of the mass number is very well reproduced by a liquid-drop type formula with curvature term.

The holographic QCD prediction for the pion distribution amplitude (DA) ${\phi }_{\mathrm{hol}}(u)$ is used to compute the pion spacelike electromagnetic form factor $F_{\pi }(Q^2)$ within the QCD light-cone sum rule method. In calculations the pion’s renormalon-based model twist-4 DA, as well as the asymptotic twist-4 DA are employed. Obtained theoretical predictions are compared with experimental data and with results of the holographic QCD.

The standard model $SU(2{)}_L\times U(1{)}_Y$ gauging of the Wess-Zumino-Witten term requires a modified counterterm when background fields, needed to generate the full set of currents, are introduced. The modified counterterm plays an essential role in properly defining covariant global currents and their anomalies. For example, it is required in order to correctly derive the gauge-invariant baryon number current and its anomalous divergence. The background fields can also be promoted to a description of the physical spin-1 vector and axial-vector mesons in QCD and the counterterm leads to novel interactions. These are (pseudo)Chern-Simons terms, such as ${ϵ}^{\mu \nu \rho \sigma }{\omega }_{\mu }{Z}_{\nu }{\partial }_{\rho }{A}_{\sigma }$ and ${ϵ}^{\mu \nu \rho \sigma }{\rho }_{\mu }^{\pm }{W}_{\nu }^{\mp }{\partial }_{\rho }{A}_{\sigma }$ that mediate new interactions between neutrinos and photons at finite baryon density.

We develop a framework for studying collective three-flavor neutrino oscillations based on the density matrix formalism. We show how techniques proven useful for collective two-flavor neutrino oscillations such as corotating frames can be applied readily to three-flavor mixing. Applying two simple assumptions and the conservation of two “lepton numbers,” we use this framework to demonstrate how the adiabatic/precession solution emerges. We illustrate with a numerical example how two stepwise spectral swaps appear naturally if the flavor evolution of the neutrino gas can be described by such a solution. For the special case where mu and tau flavor neutrinos are equally mixed and are produced with identical energy spectra and total numbers, we find that one of the spectral swaps in the three-flavor scenario agrees with that in the two-flavor scenario when appropriate mixing parameters are used. Using the corotating-frame technique we show how the adiabatic/precession solution can obtain even in the presence of a dominant ordinary matter background. With this solution we can explain why neutrino spectral swapping can be sensitive to deviations from maximal 23-mixing when the “mu-tau” matter term is significant.

A spacetime-independent variable is introduced which characterizes a Lorentz-invariant self-sustained quantum vacuum. For a perfect (Lorentz-invariant) quantum vacuum, the self-tuning of this variable nullifies the effective energy density which enters the low-energy gravitational field equations. The observed small but nonzero value of the cosmological constant may then be explained as corresponding to the effective energy density of an imperfect quantum vacuum (perturbed by, e.g., the presence of thermal matter).

In this second paper of the series, we calculate the stress tensor of excited matter, created by debris of high energy collisions at the boundary. The falling open strings, connected to receding charges, produce a nonzero stress tensor which we found analytically from time-dependent linearized Einstein equations in the bulk. It corresponds to exploding nonequilibrium matter: we discuss its behavior in some detail, including its internal energy density in a comoving frame and the “freeze-out surfaces.” We then discuss what happens for the ensemble of strings.

In the context of the AdS/CFT correspondence we discuss the gravity dual of a high energy collision in a strongly coupled $\mathcal{N}=4$ SYM gauge theory. We suggest a setting in which two colliding objects are made of nondynamical heavy quarks and antiquarks, which allows one to treat the process in classical string approximation. Collision “debris” consist of closed as well as open strings. If the latter have ends on two outgoing charges, they are being “stretched” along the collision axes. We discuss motion in AdS of some simple objects first—massless and massive particles—and then focus on open strings. We study the latter in considerable detail, concluding that they rapidly become “rectangular” in proper time-spatial rapidity $\tau -y$ coordinates with well separated fragmentation part and a near-free-falling rapidity-independent central part. Assuming that in the collisions of “walls” of charges multiple stretching strings are created, we also consider the motion of a 3D stretching membrane. We then argue that a complete solution can be approximated by two different vacuum solutions of Einstein equations, with matter membrane separating them. We identify one of these solutions with a Janik-Peschanski stretching black hole solution, and show that all objects approach its (retreating) horizon in a universal manner.

The electromagnetic nucleon to $\Delta$ transition form factors are evaluated using two degenerate flavors of dynamical Wilson fermions and using dynamical sea staggered fermions with domain-wall valence quarks. The two subdominant quadrupole form factors are evaluated for the first time in full QCD to sufficient accuracy to exclude a zero value, which is taken as a signal for deformation in the nucleon-$\Delta$ system. For the Coulomb quadrupole form factor the unquenched results begin to deviate from the quenched results at low $q^2$ indicating that dynamical lattice results are closer to experiment. This can be taken as a first confirmation of the expected importance of pion cloud contributions on this quantity.