We search for the doubly charmed baryonic decay ${\overline{B}}^0\to {\Lambda }_c^{+}{\overline{\Lambda }}_c^{-}$, in a data sample of $520\times {10}^6$ $B\overline{B}$ events accumulated at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We find no significant signal and set an upper limit of $\mathcal{B}({\overline{B}}^0\to {\Lambda }_c^{+}{\overline{\Lambda }}_c^{-})<6.2\times {10}^{-5}$ at 90% confidence level. The result is significantly below a naive extrapolation from $\mathcal{B}(B^{-}\to {\Xi }_c^0{\overline{\Lambda }}_c^{-})$ assuming a simple Cabibbo-suppression factor of $|V_{cd}/V_{cs}{|}^2$. The small branching fraction may be attributed to a suppression due to the large momentum of the baryonic decay products, which has been observed in other charmed baryonic two-body $B$ decays.

The anti-de Sitter space/conformal field theory correspondence (AdS/CFT) can potentially provide a complete formulation of string theory on a landscape of stable and metastable vacua that naturally give rise to eternal inflation. As a model for this process, we consider bubble solutions with de Sitter interiors, obtained by patching together dS and Schwarzschild–AdS solutions along a bubble wall. For an interesting subclass of these solutions the bubble wall reaches spacelike infinity in the black hole interior. Including the effects of perturbations leads to a null singularity emanating from this point. Such solutions are interpreted as states in a single CFT, and are shown to be compatible with holographic entropy bounds. The construction suggests de Sitter entropy be interpreted as the total number of degrees of freedom in effective field theory, with a novel adaptive stepsize cutoff.

Quasinormal modes of asymptotically AdS black holes can be interpreted as poles of retarded correlators in the dual gauge theory. To determine the response of the system to small external perturbations it is not enough to know the location of the poles: one also needs to know the residues. We compute them for R-charge currents and find that they are complex except for the hydrodynamic mode, whose residue is purely imaginary. For different quasinormal modes the residue grows with momentum $\mathfrak{q}$, whereas for the hydrodynamic mode it behaves as a damped oscillation with distinct zeroes at finite $\mathfrak{q}$. Similar to collective excitations at weak coupling the hydrodynamic mode decouples at short wavelengths. Knowledge of the residues allows as well to define the time scale ${\tau }_{\mathrm{H}}$ from when on the system enters the hydrodynamic regime, restricting the validity of hydrodynamic simulations to times $t>{\tau }_{\mathrm{H}}$.

We point out that the entropy of (near) extremal black holes can be interpreted as the entanglement entropy of dual conformal quantum mechanics via ${\mathrm{AdS}}_2/{\mathrm{CFT}}_1$. As an explicit example, we study near extremal Banados-Teitelboim-Zanelli black holes and derive this claim from ${\mathrm{AdS}}_3/{\mathrm{CFT}}_2$. We also analytically compute the entanglement entropy in the two dimensional CFT of a free Dirac fermion compactified on a circle at finite temperature. From this result, we clarify the relation between the thermal entropy and entanglement entropy, which is essential for the entanglement interpretation of black hole entropy.

We show that the Gauss-Bonnet term can have physical effects in four dimensions. Specifically, the entropy of a black hole acquires a correction term that is proportional to the Euler characteristic of the cross sections of the horizon. While this term is constant for a single black hole, it will be a nontrivial function for a system with dynamical topologies such as black-hole mergers: it is shown that for certain values of the Gauss-Bonnet parameter, the second law of black-hole mechanics can be violated.

Bonnor stars are regular static compact configurations in equilibrium, composed of an extremal dust fluid, i.e., a charged dust fluid where the mass density is equal to the charge density in appropriate units and up to a sign, joined to a suitable exterior vacuum solution, both within Newtonian gravity and general relativity. In four dimensions, these configurations obey the Majumdar-Papapetrou system of equations: in one case, the system is a particular setup of Newtonian gravity coupled to Coulomb electricity and electrically charged matter or fluid, in the other case, the system is a particular setup of general relativity coupled to Maxwell electromagnetism and electrically charged matter or fluid, where the corresponding gravitational potential is a specially simple function of the electric potential field and the fluid, when there is one, is made of extremal dust. Since the Majumdar-Papapetrou system can be generalized to $d$ spacetime dimensions, as has been previously done, and higher-dimensional scenarios can be important in gravitational physics, it is natural to study this type of Bonnor solutions in higher dimensions, $d\ge 4$. As a preparation, we analyze Newton-Coulomb theory with an electrically charged fluid in a Majumdar-Papapetrou context, in $d=n+1$ spacetime dimensions, with $n$ being the number of spatial dimensions. We show that within the Newtonian theory, in vacuum, the Majumdar-Papapetrou relation for the gravitational potential in terms of the electric potential, and its related Weyl relation, are equivalent, in contrast to general relativity where they are distinct. We study a class of spherically symmetric Bonnor stars within this theory. Under sufficient compactification they form point mass charged Newtonian singularities. We then study the analogue-type systems in the Einstein-Maxwell theory with an electrically charged fluid. Drawing on our previous work on the $d$-dimensional Majumdar-Papapetrou system, we restate some properties of this system. We obtain spherically symmetric Bonnor star solutions in $d=n+1$ spacetime dimensions. We show that these stars, under sufficient compactification, form $d$-dimensional quasi-black holes. We also show that in the appropriate low gravity limit theses solutions turn into the solutions of Newtonian gravity, i.e., they are quasi-Newtonian Bonnor stars. In this connection, we note that the star solutions in Majumdar-Papapetrou Newtonian gravity, when contrasted to those solutions in Majumdar-Papapetrou general relativity, display clearly the branching off of the high density objects that may arise in the strong field regime of each theory, mild singularities in one theory, quasi-black holes in the other. Another important feature worth mentioning is that, whereas there are no solutions for Newtonian or relativistic stars supported by degenerate pressure in higher dimensions, higher-dimensional Bonnor stars, supported by electric repulsion, do indeed have solutions within Newtonian gravity and general relativity. So the existence of stars in higher dimensions depends on the number of dimensions itself, and on the underlying field content of those stars.

We present a model where early inflation and late accelerating expansion of the Universe are driven by the real and imaginary parts of a single complex scalar field, which we identified as the inflaton and phantom field, respectively. This inflaton-phantom unification is protected by an internal $SO(1,1)$ symmetry, with the two cosmological scalars appearing as the degrees of freedom of a sole fundamental representation. The unification symmetry allows to build successful potentials. We observe that our theory provides a matter-phantom duality, which transforms scalar matter cosmological solutions into phantom solutions and vice versa. We also suggest that a complete unification of all scalar fields of cosmological interest is yet possible under a similar footing.

The process of identifying a time variable in time-reparameterization invariant theories results in great ambiguities about the actual laws of physics described by a given theory. A theory set up to describe one set of physical laws can equally well be interpreted as describing any other laws of physics by making a different choice of time variable or clock. In this article we demonstrate how this “clock ambiguity” arises and then discuss how one might still hope to extract specific predictions about the laws of physics even when the clock ambiguity is present. We argue that a requirement of quasiseparability should play a critical role in such an analysis. As a step in this direction, we compare the Hamiltonian of a local quantum field theory with a completely random Hamiltonian. We find that any random Hamiltonian (constructed in a sufficiently large space) can yield a “good enough” approximation to a local field theory. Based on this result we argue that theories that suffer from the clock ambiguity may in the end provide a viable fundamental framework for physics in which locality can be seen as a strongly favored (or predicted) emergent behavior. We also speculate on how other key aspects of known physics such as gauge symmetries and Poincare invariance might be predicted to emerge in this framework.

Temperature anisotropies in the cosmic microwave background (CMB) are affected by the late integrated Sachs-Wolfe (lISW) effect caused by any time variation of the gravitational potential on linear scales. Dark energy is not the only source of lISW, since massive neutrinos induce a small decay of the potential on small scales during both matter and dark energy domination. In this work, we study the prospect of using the cross correlation between CMB and galaxy-density maps as a tool for constraining the neutrino mass. On the one hand massive neutrinos reduce the cross-correlation spectrum because free-streaming slows down structure formation; on the other hand, they enhance it through their change in the effective linear growth. We show that in the observable range of scales and redshifts, the first effect dominates, but the second one is not negligible. We carry out an error forecast analysis by fitting some mock data inspired by the Planck satellite, Dark Energy Survey (DES) and Large Synoptic Survey Telescope (LSST). The inclusion of the cross correlation data from Planck and LSST increases the sensitivity to the neutrino mass $m_{\nu }$ by 38% (and to the dark energy equation of state $w$ by 83%) with respect to Planck alone. The correlation between Planck and DES brings a far less significant improvement. This method is not potentially as good for detecting $m_{\nu }$ as the measurement of galaxy, cluster, or cosmic shear power spectra, but since it is independent and affected by different systematics, it remains potentially interesting if the total neutrino mass is of the order of 0.2 eV; if instead it is close to the lower bound from atmospheric oscillations, $m_{\nu }\sim 0.05\mathrm{eV}$, we do not expect the ISW-galaxy correlation to be ever sensitive to $m_{\nu }$.

Near comoving wave number $k$, the gravitational-wave background (GWB) from inflation carries information about the physical conditions near two moments in cosmic history: the moment when $k$ “left the horizon” during inflation, and the moment when it “re-entered the horizon” after inflation. We investigate the extent to which this information can be extracted if the GWB is measured by a combination of cosmic-microwave-background polarization experiments on large scales and space-based laser-interferometer experiments on small scales. To disentangle this information, we derive a new gravitational-wave transfer function that incorporates a number of physical effects that were treated less accurately, less generally, or were missing altogether in previous treatments. In particular, it incorporates: (i) dark energy with time-varying equation of state $w(z)$; (ii) tensor anisotropic stress due to free-streaming relativistic particles in the early universe; and (iii) a variety of physical effects that cause deviations from the standard equation of state $w=1/3$ during the radiation era. Based on this transfer function, we consider the degree to which the GWB can be used to test inflation and to probe the “primordial dark age” between the end of inflation and the electroweak phase transition.

Following the analogy of the “$db$” triangle in the quark-mixing case, we have explored the construction of the “${\nu }_2.{\nu }_3$” leptonic unitarity triangle using the Maki-Nakagawa-Sakata matrix obtained by Bjorken et al. through generalization of the tribimaximal scenario. In particular, for the $U_{e3}$ range 0.05–0.15, the existence of the leptonic unitarity triangle indicates a fairly good possibility of having nonzero $CP$ violation.

Based on previous studies deriving the chiral Lagrangian for pseudoscalar mesons from the first principle of QCD, we derive an electroweak chiral Lagrangian and build up a formulation for computing its coefficients from a one-doublet technicolor model and a schematic topcolor-assisted technicolor model. We find that coefficients of the electroweak chiral Lagrangian for the topcolor-assisted technicolor model are divided into three parts: direct TC2 interaction part, TC1 and TC2 induced effective $Z^{\prime }$ particle contribution part, and ordinary quarks contribution part. The first two parts are computed in this paper. We show that the direct TC2 interaction part is the same as that in the one-doublet technicolor model, while effective $Z^{\prime }$ contributions are at least proportional to the $p^2$ order parameter ${\beta }_1$ in the electroweak chiral Lagrangian. Typical features of the topcolor-assisted technicolor model are that it only allows positive $T$ and $U$ parameters, the $T$ parameter varies in the range $0\sim 1/(25\alpha )$, and the upper bound of $T$ parameter will decrease as long as $Z^{\prime }$ mass become large. The $S$ parameter can be either positive or negative depending on whether the $Z^{\prime }$ mass is large or small. The $Z^{\prime }$ mass is bounded above and the upper bound depends on the value of the $T$ parameter. We obtain the values for all coefficients of the electroweak chiral Lagrangian up to the order of $p^4$.

The Berger model of perturbative fragmentation of quarks to pions is improved by providing an absolute normalization and keeping all terms in a ($1-z$) expansion, which makes the calculation valid at all values of fractional pion momentum $z$. We also replace the nonrelativistic wave function of a loosely bound pion by the more realistic procedure of projecting to the light-cone pion wave function, which in turn is taken from well known models. The full calculation does not confirm the $(1-z{)}^2$ behavior of the fragmentation function (FF) predicted in [E. L. Berger, Z. Phys. C 4, 289 (1980); Phys. Lett. 89B, 241 (1980] for $z>0.5$, and only works at very large $z>0.95$, where it is in reasonable agreement with phenomenological FFs. Otherwise, we observe quite a different $z$-dependence which grossly underestimates data at smaller $z$. The disagreement is reduced after the addition of pions from decays of light vector mesons, but still remains considerable. The process dependent higher twist terms are also calculated exactly and found to be important at large $z$ and/or $p_T$.

Vector and axial form factors in the quark resonance model are analyzed with a combination of theoretical and phenomenological arguments. The new form of form factors is deduced from $\Delta (1232)$ excitation models and available data. The vector part is shown to agree with the resonant contribution to electron-proton inclusive $F_2$ data. The axial part is obtained by finding a simultaneous fit to ANL and BNL $\frac{d\sigma }{d{Q}^2}$ neutrino scattering data. The best fit corresponds to $C_5^A(0)=0.88$ in the Rarita-Schwinger formalism.

We study the constraint arising from the recently observed $D\mathrm{\text{−}}\overline{D}$ mixing in the context of supersymmetric models with left-right symmetry. In these models, the supersymmetric contributions in the mixing amplitudes of $D\mathrm{\text{−}}\overline{D}$, $K\mathrm{\text{−}}\overline{K}$ and $B\mathrm{\text{−}}\overline{B}$ are all correlated. We compare the constraint from the $D\mathrm{\text{−}}\overline{D}$ mixing with the $K\mathrm{\text{−}}\overline{K}$ mixing and find that the $D\mathrm{\text{−}}\overline{D}$ mixing constrains the maximal supersymmetric contribution to the $B_s\mathrm{\text{−}}{\overline{B}}_s$ mixing amplitude. The maximal supersymmetric contribution can allow a large CP phase of $B_s\mathrm{\text{−}}{\overline{B}}_s$ mixing which agrees with the recent measurement of the CP asymmetry of $B_s\to J/\psi \varphi$ decay.

We consider the effects of graviton multiplet fields on transitions between string gas phases. Focusing on the dilaton field, we show that it may obstruct transitions between different thermodynamic phases of the string gas, because the sign of its dimensionally reduced, $T$-duality invariant, part is conserved when the energy density of the Universe is positive. Thus, many interesting solutions for which this sign is positive end up in a future curvature singularity. Because of this, some of the thermodynamic phases of the usual gravitating string gases behave like superselection sectors. For example, a past-regular Hagedorn phase and an expanding Friedmann-Robertson-Walker (FRW) phase dominated by string momentum modes cannot be smoothly connected in the framework of string cosmology with positive sources. The singularity separates them like a geometric precipice in the moduli space, preventing the dynamics of the theory from bridging across. Sources which simultaneously violate the positivity of energy and null energy condition (NEC) could modify these conclusions. We provide a quantitative measure of positivity of energy and NEC violations that would be necessary for such transitions. These effects must dominate the Universe at the moment of transition, altering the standard gas pictures. At present, it is not known how to construct such sources from first principles in string theory.

Current neutrino oscillation data indicate the existence of two large lepton mixing angles, while Kobayashi-Maskawa matrix elements are all small. Here we show how supersymmetric SO(10) with extra chiral singlets can easily reconcile large lepton mixing angles with small quark mixing angles within the framework of the successful Fritzsch ansatz. Moreover, we show how this is fully consistent with the thermal leptogenesis scenario, avoiding the so-called gravitino problem. A sizable asymmetry can be generated at scales as low as possible within the leptogenesis mechanism. We present our results in terms of the leptonic $CP$ violation parameter that characterizes neutrino oscillations.

We study the weak productions of novel heavy mesons, such as ${\eta }_c^{\prime }$, $h_c$, $h_c^{\prime }$, ${\chi }_{c0}^{\prime }$, $X(3940)$, $Y(3940)$, $X(3872)$, and $Y(4260)$, in the semileptonic $B_c$ decays. Since there is still no definite answer for the components of $X(3940)$, $Y(3940)$, $X(3872)$, $Y(4260)$ so far, we will assign them as excited charmonium states with the possible quantum numbers constrained by the current experiments. As for the weak transition form factors, we calculate them in the framework of the light-cone QCD sum rules approach, which has proven to be a powerful tool to deal with the nonperturbative hadronic matrix element. Our results indicate that different interpretations of $X(3940)$ can result in a remarkable discrepancy of the production rate in the $B_c$ decays, which would help to clarify the inner structure of the $X(3940)$ with the forthcoming LHC-b experiments. Besides, the predicted large weak production rates of $X(3872)$ and $Y(3940)$ in $B_c$ decays and the small semileptonic decay rate for $B_c\to Y(4260)$ all depend on their quantum number $J^{PC}$ assignments. Moreover, the $S-D$ mixing of various vector charmonium states in the weak decay of $B_c$ is also discussed in this work. The future experimental measurements of these decays will test the inner structures of these particles, according to our predictions here.

The nucleon strange and antistrange distribution asymmetry is an important issue in the study of the nucleon structure. In this work, we show that the heavy-quark recombination processes from a perturbative QCD picture can give a sizable influence on the measurement of the nucleon strangeness asymmetry from charged-current charm production processes, such as the CCFR and NuTeV dimuon measurements. When the influence of heavy-quark recombination is considered, a positive effective $\delta S_{\mathrm{HR}}^{-}$ should be added to the initially extracted strangeness asymmetry $S^{-}\equiv \int dx[s(x)-\overline{s}(x)]x$, supporting the strangeness asymmetry $S^{-}$ being positive, which is helpful to explain the NuTeV anomaly within the framework of the standard model.

We find the three-dimensional gravity dual of a process in which two clouds of ($1+1$)-dimensional conformal matter moving in opposite directions collide. This gives the most general conformally invariant holographic flow in the ($1+1$)-dimensional boundary theory in terms of two arbitrary functions. With a suitable choice of the arbitrary functions the process can be interpreted as an opaque collision of two extended systems with central, fragmentation and interaction regions. Comparison with classical gluon field calculations relates the size of the system with the saturation scale.