Following a similar recent analysis for $CP$ violation in the electroweak sector of the standard model, we estimate the naturalness of a magnitude of $CP$ violation (measured by the Jarlskog invariant $J$) close to the observed value in extensions of the standard model with left-right symmetry, such as the Pati-Salam model, where quark mass matrices are not Hermitian in general. We construct a simple and natural measure on the space of complex matrices which is both geometrically motivated and uses the observed quark mass hierarchy. We find that, unlike in the case of the standard model where the observed value for $J$ seemed rather typical, one would now expect to observe $|J|<{10}^{-7}$, clearly in conflict with the observed value $J\approx 3\times {10}^{-5}$. The crucial difference in the calculation lies in the non-Hermiticity of mass matrices that modifies the measure. We conclude that one would need additional assumptions modifying the measure to reproduce the observed value, and that in this sense the standard model is preferred to certain classes of left-right symmetric extensions: It does not need additional assumptions to explain the magnitude of $CP$ violation.

We apply the thermal field theory methods to study the propagation of photons in a plasma layer, that is a plasma in which the electrons are confined to a two-dimensional plane sheet. We calculate the photon self-energy and determine the appropriate expression for the photon propagator in such a medium, from which the properties of the propagating modes are obtained. The formulas for the photon dispersion relations and polarization vectors are derived explicitly in some detail for some simple cases of the thermal distributions of the charged particle gas, and appropriate formulas that are applicable in more general situations are also given.

Measurements at $B$ factories have provided important constraints on new physics in several rare processes involving the $B$ meson. New physics, if present in the $b$ quark sector may also affect the top sector. In an effective Lagrangian approach, we write down operators, where effects in the bottom and the top sector are related. Assuming the couplings of the operators to be of the same size as the weak coupling $g$ of the standard model and taking into account constraints on new physics from the bottom sector as well as top branching ratios, we make predictions for the rare top decays $t\to cV$, where $V=\gamma$, $Z$. We find branching fractions for these decays within possible reach of the LHC. Predictions are also made for $t\to sW$.

Magnetic moments of the low lying and charmed spin ${\frac{1}{2}}^{+}$ and spin ${\frac{3}{2}}^{+}$ baryons have been calculated in the $SU(4)$ chiral constituent quark model ($\chi \mathrm{CQM}$) by including the contribution from $c\overline{c}$ fluctuations. Explicit calculations have been carried out for the contribution coming from the valence quarks, “quark sea” polarizations and their orbital angular momentum. The implications of such a model have also been studied for magnetic moments of the low lying spin ${\frac{3}{2}}^{+}\to {\frac{1}{2}}^{+}$ and ${\frac{1}{2}}^{+}\to {\frac{1}{2}}^{+}$ transitions as well as the transitions involving charmed baryons. The predictions of $\chi \mathrm{CQM}$ not only give a satisfactory fit for the baryons where experimental data is available but also show improvement over the other models. In particular, for the case of $\mu (p)$, $\mu ({\Sigma }^{+})$, $\mu ({\Xi }^0)$, $\mu (\Lambda )$, Coleman-Glashow sum rule for the low lying spin ${\frac{1}{2}}^{+}$ baryons and $\mu ({\Delta }^{+})$, $\mu ({\Omega }^{-})$ for the low lying spin ${\frac{3}{2}}^{+}$ baryons, we are able to achieve an excellent agreement with data. For the spin ${\frac{1}{2}}^{+}$ and spin ${\frac{3}{2}}^{+}$ charmed baryon magnetic moments, our results are consistent with the predictions of the QCD sum rules, light cone sum rules and spectral sum rules. For the cases where light quarks dominate in the valence structure, the sea and orbital contributions are found to be fairly significant however, they cancel in the right direction to give the correct magnitude of the total magnetic moment. On the other hand, when there is an excess of heavy quarks, the contribution of the quark sea is almost negligible, for example, $\mu ({\Omega }_c^0)$, $\mu ({\Lambda }_c^{+})$, $\mu ({\Xi }_c^{+})$, $\mu ({\Xi }_c^0)$, $\mu ({\Omega }_{cc}^{+})$, $\mu ({\Omega }^{-})$, $\mu ({\Omega }_c^{*0})$, $\mu ({\Omega }_{cc}^{*+})$, and $\mu ({\Omega }_{ccc}^{*++})$. The effects of configuration mixing and quark masses have also been investigated.

We report a search for the decays $B^0\to K^{*0}{\overline{K}}^{*0}$ and $B^0\to K^{*0}{K}^{*0}$. We also measure other charmless decay modes with $K^{+}{\pi }^{-}{K}^{-}{\pi }^{+}$ and $K^{+}{\pi }^{-}{K}^{+}{\pi }^{-}$ final states. The results are obtained from a data sample containing $657\times {10}^6$ $B\overline{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We set upper limits on the branching fractions for $B^0\to K^{*0}{\overline{K}}^{*0}$ and $B^0\to K^{*0}{K}^{*0}$ of $0.81\times {10}^{-6}$ and $0.20\times {10}^{-6}$, respectively, at the 90% confidence level.

We investigate the propagation of a spacelike flavor current in a strongly coupled $\mathcal{N}=2$ super Yang-Mills plasma using the D3-D7 brane model at finite temperature. The partonic contribution to the plasma structure functions is obtained from the imaginary part of the retarded current-current commutator. At high temperatures we find a nonvanishing result, for a high energy current, indicating absorption of the flavor current by the quark constituents of the plasma. At low temperatures there is no quark contribution to the plasma structure functions.

We show that Polchinski equations in the $D$-dimensional matrix scalar field theory can be reduced at large $N$ to the Hamiltonian equations in a ($D+1$)-dimensional theory. In the subsector of the $\mathrm{Tr}{\varphi }^l$ (for all $l$) operators we find the exact form of the corresponding Hamiltonian. The relation to the holographic renormalization group is discussed.

Recently we observed a crossover transition (in the Fayet-Iliopoulos parameter) from weak to strong coupling in $\mathcal{N}=2$ supersymmetric QCD with the $\mathrm{U}(N)$ gauge group and $N_f>N$ quark flavors. At strong coupling this theory can be described by a dual non-Abelian weakly coupled supersymmetric QCD with the dual gauge group $\mathrm{U}(N_f-N)$ and $N_f$ light dyon flavors. Both theories support non-Abelian strings. We continue the study of confinement dynamics in these theories, in particular, metamorphoses of excitation spectra, from a different side. A number of results obtained previously are explained, enhanced and supplemented by analyzing the world-sheet dynamics on the non-Abelian confining strings. The world-sheet theory is the two-dimensional $\mathcal{N}=(2,2)$ supersymmetric weighted $CP(N_f-1)$ model. We explore the vacuum structure and kinks on the world sheet, corresponding to confined monopoles in the bulk theory. We show that (in the equal quark mass limit) these kinks fall into the fundamental representation of the unbroken global $\mathrm{SU}(N)\times \mathrm{SU}(N_f-N)\times \mathrm{U}(1)$ group. This result confirms the presence of extra stringy meson states in the adjoint representation of the global group in the bulk theory. The non-Abelian bulk duality is in one-to-one correspondence with a duality taking place in the $\mathcal{N}=(2,2)$ supersymmetric weighted $CP(N_f-1)$ model.

We study fluctuation modes in ten-dimensional Yang-Mills theory with a higher derivative term for the gauge field. We consider the ten-dimensional space-time to be a product of a four-dimensional space-time and six-dimensional sphere which exhibits dynamical compactification. Because of the isometry on $S^6$, there are flat directions corresponding to the Nambu-Goldstone zero modes in the effective theory on the solution. The zero modes are absorbed into gauge fields and form massive vector fields as a consequence of the Higgs-Kibble mechanism. The mass of the vector fields is proportional to the inverse of the radius of the sphere and larger than the mass scale set by the radius because of the higher derivative term.

A restriction of the baby Skyrme model consisting of the quartic and potential terms only is investigated in detail for a wide range of potentials. Further, its properties are compared with those of the corresponding full baby Skyrme models. We find that topological (charge) as well as geometrical (nucleus/shell shape) features of baby Skyrmions are captured already by the soliton solutions of the restricted model. Further, we find a coincidence between the compact or noncompact nature of solitons in the restricted model, on the one hand, and the existence or nonexistence of multi-Skyrmions in the full baby Skyrme model, on the other hand.

Exact analytic expressions for planetary orbits and light trajectories in the Schwarzschild geometry are presented. A new parameter space is used to characterize all possible planetary orbits. Different regions in this parameter space can be associated with different characteristics of the orbits. The boundaries for these regions are clearly defined. Observational data can be directly associated with points in the regions. A possible extension of these considerations with an additional parameter for the case of Kerr geometry is briefly discussed.

Heavy partners of the top quark are a common prediction of many models in which a new strongly-coupled sector is responsible for the breaking of the electroweak symmetry. In this paper, we investigate their experimental signature at the LHC, focusing on the particularly clean channel of same-sign dileptons. We show that, thanks to a strong interaction with the top quark which allows them to be singly produced at a sizable rate, the top partners will be discovered at the LHC if their mass is below 1.5 TeV, higher masses being possible in particularly favorable (but plausible) situations. Since the partners are expected to be lighter in both the Higgsless and composite-Higgs scenarios, then one of same-sign dileptons is found to be a very promising channel in which these models could be tested. We also discuss several experimental signatures which would allow, after the discovery of the excess, to attribute it uniquely to the top partners production and to measure the relevant physical parameters, i.e. the top partners’ masses and couplings. We believe that our results constitute a valid starting point for a more detailed experimental study.

We analyze the spectral moments of the $V-A$ two-point correlation function. Using all known short-distance constraints and the most recent experimental data from tau decays, we determine the lowest spectral moments, trying to assess the uncertainties associated with the so-called violations of quark-hadron duality. We have generated a large number of acceptable spectral functions, satisfying all conditions, and have used them to extract the wanted hadronic parameters through a careful statistical analysis. We obtain accurate values for the $\chi \mathrm{PT}$ couplings $L_{10}$ and $C_{87}$, and a realistic determination of the dimension six and eight contributions in the operator product expansion, ${\mathcal{O}}_6=(-{5.4}_{-1.6}^{+3.6})·{10}^{-3}{\mathrm{GeV}}^6$ and ${\mathcal{O}}_8=(-{8.9}_{-7.4}^{+12.6})·{10}^{-3}{\mathrm{GeV}}^8$, showing that the duality-violation effects have been underestimated in previous literature.

In this work, we discuss the contribution of the mesonic loops to the decay rates of ${\chi }_{c1}\to \varphi \varphi$, $\omega \omega$, which are suppressed by the helicity selection rules and ${\chi }_{c1}\to \varphi \omega$, which is a double-Okubo-Zweig-Iizuka forbidden process. We find that the mesonic loop effects naturally explain the clear signals of ${\chi }_{c1}\to \varphi \varphi$, $\omega \omega$ decay modes observed by the BES Collaboration. Moreover, we investigate the effects of the $\omega -\varphi$ mixing, which may result in the order of magnitude of the branching ratio $\mathrm{BR}({\chi }_{c1}\to \omega \varphi )$ being ${10}^{-7}$. Thus, we are waiting for the accurate measurements of the $\mathrm{BR}({\chi }_{c1}\to \omega \omega )$, $\mathrm{BR}({\chi }_{c1}\to \varphi \varphi )$, and $\mathrm{BR}({\chi }_{c1}\to \omega \varphi )$, which may be very helpful for testing the long-distant contribution and the $\omega -\varphi$ mixing in ${\chi }_{c1}\to \varphi \varphi$, $\omega \omega$, $\omega \varphi$ decays.

A possible resolution of the flavor puzzle is that the fermion mass hierarchy can be dynamically generated through the coupling of the first-two-generation fields to a strongly coupled sector, which is approximately conformally invariant and leads to large anomalous dimensions for the first-two-generation fields over a large range of energies. We investigate the possibility of using the same sector to also break supersymmetry. We show that this automatically gives an “inverted hierarchy” in which the first-two-generation squarks and sleptons are much heavier than the other superpartners. Implementing this construction generically requires some fine-tuning in order to satisfy the constraints on flavor-changing neutral currents at the same time as solving the hierarchy problem. We show that this fine-tuning can be reduced to be milder than the percent level by making some technically natural assumptions about the form of the strongly coupled sector and its couplings to the standard model.

The late part of the gravitational wave signal of binary neutron-star (or black-hole–neutron-star) inspirals can in principle yield crucial information on the nuclear equation of state via its dependence on relativistic tidal parameters. In the hope of analytically describing the gravitational wave phasing during the late inspiral (essentially up to merger) we propose an extension of the effective one body (EOB) formalism which includes tidal effects. We compare the prediction of this tidal-EOB formalism to recently computed nonconformally flat quasiequilibrium circular sequences of binary neutron-star systems. Our analysis suggests the importance of higher-order (post-Newtonian) corrections to tidal effects, even beyond the first post-Newtonian order, and their tendency to significantly increase the “effective tidal polarizability” of neutron stars. We propose to use the EOB description up to the moment where the tidally deformed compact objects formally enter “into contact.” We compare the EOB predictions to some recently advocated, nonresummed, post-Newtonian based (“Taylor-T4”) description of the phasing of inspiralling systems. This comparison shows the strong sensitivity of the late-inspiral phasing to the choice of the analytical model. A sufficiently accurate numerical–relativity–“calibrated” EOB model might, however, give us a reliable analytical description of the late inspiral of compact binaries (and might also help in predicting the conditions necessary for the generation of short gamma-ray bursts).

We discuss new exact solutions of a three-parameter nonminimal Einstein-Maxwell model. The solutions describe static spherically symmetric objects with and without center, supported by an electric field nonminimally coupled to gravity. We focus on a unique one-parameter model, which admits an exact solution for a traversable electrically charged wormhole connecting two universes, one asymptotically flat the other asymptotically de Sitter ones. The relation between the asymptotic mass and charge of the wormhole and its throat radius is analyzed. The wormhole solution found is thus a nonminimal realization of Wheeler’s idea about charge without charge and shows that, if the world is somehow nonminimal in the coupling of gravity to electromagnetism, then wormhole appearance, or perhaps construction, is possible.