We propose a model to describe diffractive events in hadron-hadron collisions where a rapidity gap is surrounded by two jets. The hard color-singlet object exchanged in the t-channel and responsible for the rapidity gap is described by the perturbative QCD Balitsky-Fadin-Kuraev-Lipatov Pomeron, including corrections due to next-to-leading logarithms. We allow the rapidity gap to be smaller than the interjet rapidity interval, and the corresponding soft radiation is modeled using the HERWIG Monte Carlo. Our model is able to reproduce all Tevatron data, and allows one to estimate the jet-gap-jet cross section at the LHC.

We address the puzzle of $\sigma ({\chi }_{c1})/\sigma ({\chi }_{c2})$ ratio at the collider and fixed-target experiments. We consider several factors that can affect the predicted ratio of the production rates. In particular, we discuss the effect of ${\chi }_{cJ}$ polarization, the effect of including next-to-leading order contributions, and the effect of probably different ${\chi }_{c1}$ and ${\chi }_{c2}$ wave functions.

Tribimaximal leptonic mixing is a mass-independent mixing scheme consistent with the present solar and atmospheric neutrino data. By conveniently decomposing the effective neutrino mass matrix associated to it, we derive generic predictions in terms of the parameters governing the neutrino masses. We extend this phenomenological analysis to other mass-independent mixing schemes which are related to the tribimaximal form by a unitary transformation. We classify models that produce tribimaximal leptonic mixing through the group structure of their family symmetries in order to point out that there is often a direct connection between the group structure and the phenomenological analysis. The type of seesaw mechanism responsible for neutrino masses plays a role here, as it restricts the choices of family representations and affects the viability of leptogenesis. We also present a recipe to generalize a given tribimaximal model to an associated model with a different mass-independent mixing scheme, which preserves the connection between the group structure and phenomenology as in the original model. This procedure is explicitly illustrated by constructing toy models with the transpose tribimaximal, bimaximal, golden ratio, and hexagonal leptonic mixing patterns.

The magnetized MINOS Near Detector, at a depth of 225 mwe, is used to measure the atmospheric muon charge ratio. The ratio of observed positive to negative atmospheric muon rates, using 301 days of data, is measured to be $1.266\pm 0.001(\mathrm{stat}{)}_{-0.014}^{+0.015}(\mathrm{syst})$. This measurement is consistent with previous results from other shallow underground detectors and is $0.108\pm 0.019(\mathrm{stat}+\mathrm{syst})$ lower than the measurement at the functionally identical MINOS Far Detector at a depth of 2070 mwe. This increase in charge ratio as a function of depth is consistent with an increase in the fraction of muons arising from kaon decay for increasing muon surface energies.

The ratio of the cross section for $p\overline{p}$ interactions producing a $Z$ boson and at least one $b$-quark jet to the inclusive $Z+\mathrm{\text{jet}}$ cross section is measured using $4.2{\mathrm{fb}}^{-1}$ of $p\overline{p}$ collisions collected with the D0 detector at the Fermilab Tevatron collider at $\sqrt{s}=1.96\mathrm{TeV}$. The $Z\to {\ell }^{+}{\ell }^{-}$ candidate events with at least one $b$ jet are discriminated from $Z+\mathrm{\text{charm}}$ and light jet(s) events by a novel technique that exploits the properties of the tracks associated to the jet. The measured ratio is $0.0193\pm 0.0027$ for events having a jet with transverse momentum $p_T>20\mathrm{GeV}$ and pseudorapidity $|\eta |\le 2.5$, which is the most precise to date and is consistent with theoretical predictions.

We study the properties of fermion correlators in a boundary theory dual to the Reissner-Nordström ${\mathrm{AdS}}_{d+1}$ background in the presence of a bulk dipole (Pauli) interaction term with strength $p$. We show that by simply changing the value of the parameter $p$ we can tune continuously from a Fermi liquid (small $p$), to a marginal-Fermi liquid behavior at a critical value of $p$, to a generic non-Fermi liquid at intermediate values of $p$, and finally to a Mott insulator at large values of the bulk Pauli coupling. As all of these phases are seen in the cuprate phase diagram, the holographic model we study has the key elements of the strong-coupling physics typified by Mott systems. In addition, we extend our analysis to finite temperature and show that the Mott gap closes. Of particular interest is that it closes when the ratio of the gap to the critical temperature is of the order of 10. This behavior is very much similar to that observed in the classic Mott insulator ${\mathrm{VO}}_2$. We then analyze the nonanalyticities of the boundary theory fermion correlators for generic values of frequency and momentum by calculating the quasinormal modes of the bulk fermions. Not surprisingly, we find no evidence for the dipole interaction inducing an instability in the boundary theory. Finally, we briefly consider the introduction of superconducting condensates and find that, in that case, the fermion gap is driven by scalar-fermion couplings rather than by the Pauli coupling.

We derive model-independent lower bounds on the stress tensor central charge $C_T$ in terms of the operator content of a 4-dimensional conformal field theory. More precisely, $C_T$ is bounded from below by a universal function of the dimensions of the lowest and second-lowest scalars present in the conformal field theory. The method uses the crossing symmetry constraint of the 4-point function, analyzed by means of the conformal block decomposition.

We study the holographic QCD model, which contains a quadratic term $-\sigma z^2$ and a logarithmic term $-c_0\log [(z_{\mathrm{IR}}-z)/z_{\mathrm{IR}}]$ with an explicit infrared cutoff $z_{\mathrm{IR}}$ in the deformed ${\mathrm{AdS}}_5$ warp factor. We investigate the heavy-quark potential for three cases, i.e., with only a quadratic correction, with both quadratic and logarithmic corrections, and with only a logarithmic correction. We solve the dilaton field and dilation potential from the Einstein equation and investigate the corresponding beta function in the Gürsoy-Kiritsis-Nitti framework. Our studies show that in the case with only a quadratic correction, a negative $\sigma$ or the Andreev-Zakharov model is favored to fit the heavy-quark potential and to produce the QCD beta function at 2-loop level; however, the dilaton potential is unbounded in the infrared regime. One interesting observation for the case of positive $\sigma$ is that the corresponding beta function exists in an infrared fixed point. In the case with only a logarithmic correction, the heavy-quark Cornell potential can be fitted very well, the corresponding beta function agrees with the QCD beta function at 2-loop level reasonably well, and the dilaton potential is bounded from below in the infrared. At the end, we propose a more compact model which has only a logarithmic correction in the deformed warp factor and has less free parameters.

We analyze the mass varying neutrino scenario. We consider a minimal model of massless Dirac fermions coupled to a scalar field, mainly in the framework of finite-temperature quantum field theory. We demonstrate that the mass equation we find has nontrivial solutions only for special classes of potentials, and only within certain temperature intervals. We give most of our results for the Ratra-Peebles dark energy (DE) potential. The thermal (temporal) evolution of the model is analyzed. Following the time arrow, the stable, metastable, and unstable phases are predicted. The model predicts that the present Universe is below its critical temperature and accelerates. At the critical point, the Universe undergoes a first-order phase transition from the (meta)stable oscillatory regime to the unstable rolling regime of the DE field. This conclusion agrees with the original idea of quintessence as a force making the Universe roll towards its true vacuum with a zero $\Lambda$ term. The present mass varying neutrino scenario is free from the coincidence problem, since both the DE density and the neutrino mass are determined by the scale $M$ of the potential. Choosing $M\sim {10}^{-3}\mathrm{eV}$ to match the present DE density, we can obtain the present neutrino mass in the range $m\sim {10}^{-2}–1\mathrm{eV}$ and consistent estimates for other parameters of the Universe.

In this work, we have investigated the nature of the electroweak phase transition in the $U(1)$ extended minimal supersymmetric standard model without introducing any exotic fields. The effective potential has been estimated exactly at finite temperature taking into account the whole particle spectrum. For reasonable values of the lightest Higgs and neutralino, we found that the electroweak phase transition could be strongly first order due to: (1) the interactions of the singlet with the doublets in the effective potential, and (2) the evolution of the wrong vacuum that delays the transition.

There exists a formulation of the Maxwell theory in terms of two vector potentials, one electric and one magnetic. The action is then manifestly invariant under electric-magnetic duality transformations, which are rotations in the two-dimensional internal space of the two potentials, and local. We ask the question: Can duality be gauged? The only known and battle-tested method of accomplishing the gauging is the Noether procedure. In its decanted form, it amounts to turning on the coupling by deforming the Abelian gauge group of the free theory, out of whose curvatures the action is built, into a non-Abelian group which becomes the gauge group of the resulting theory. In this article, we show that the method cannot be successfully implemented for electric-magnetic duality. We thus conclude that, unless a radically new idea is introduced, electric-magnetic duality cannot be gauged. The implication of this result for supergravity is briefly discussed.

First-order quantum correction to the Larmor radiation is investigated on the basis of the scalar QED on a homogeneous background of a time-dependent electric field, which is a generalization of a recent work by Higuchi and Walker so as to be extended for an accelerated charged particle in a relativistic motion. We obtain a simple approximate formula for the quantum correction in the limit of the relativistic motion when the direction of the particle motion is parallel to that of the electric field.

We present a family of static and evolving spherically symmetric Lorentzian wormhole solutions in $N+1$-dimensional Einstein gravity. In general, for static wormholes, we require that, at least, the radial pressure has a barotropic equation of state of the form $p_r={\omega }_r\rho$, where the state parameter ${\omega }_r$ is constant. On the other hand, it is shown that, in any dimension $N\ge 3$, with $\varphi (r)=\Lambda =0$ and anisotropic barotropic pressure with constant state parameters, static wormhole configurations are always asymptotically flat spacetimes, while, in $2+1$ gravity, there are not only asymptotically flat static wormholes but also more general ones. In this case, the matter sustaining the three-dimensional wormhole may be only a pressureless fluid. In the case of evolving wormholes with $N\ge 3$, the presence of a cosmological constant leads to an expansion or contraction of the wormhole configurations: for positive cosmological constants, we have wormholes which expand forever, and, for negative cosmological constants, we have wormholes which expand to a maximum value and then recollapse. In the absence of a cosmological constant, the wormhole expands with constant velocity, i.e., without acceleration or deceleration. In $2+1$ dimensions, the expanding wormholes always have an isotropic and homogeneous pressure, depending only on the time coordinate.

We perform the Hamiltonian analysis of nonrelativistic covariant Hořava-Lifshitz gravity in the formulation presented recently in arXiv:1009.4885. We argue that the resulting Hamiltonian structure is in agreement with the original construction of nonrelativistic covariant Hořava-Lifshitz gravity presented in arXiv:1007.2410. Then we extend this construction to the case of restricted-foliation-preserving diffeomorphism invariant Hořava-Lifshitz theory. We find a well behaved Hamiltonian system with the number of the first- and the second-class constraints that ensure the correct number of physical degrees of freedom of gravity.

The time-dependent metric of a cosmic string leads to an effective interaction between the string and photons—the “gravitational Aharonov-Bohm” effect—and causes cosmic strings to emit light. We evaluate the radiation of pairs of photons from cosmic strings and find that the emission from cusps, kinks and kink-kink collisions occurs with a flat spectrum at all frequencies up to the string scale. Further, cusps emit a beam of photons, kinks emit along a curve, and the emission at a kink-kink collision is in all directions. The emission of light from cosmic strings could provide an important new observational signature of cosmic strings that is within reach of current experiments for a range of string tensions.

We calculate the shift in the atomic energy levels induced by the presence of a scalar field which couples to matter and photons. We find that a combination of atomic measurements can be used to probe both these couplings independently. A new and stringent bound on the matter coupling springs from the precise measurement of the $1s$ to $2s$ energy level difference in the hydrogen atom, while the coupling to photons is essentially constrained by the Lamb shift. For a range of masses these constraints are not as stringent as those from fifth force experiments or optical astrophysical and laboratory measurements. However, they have the advantage that they are universal, applying to all scalars, even those that hide their effects dynamically from fifth force searches, such as the chameleon and Galileon models. Combining these constraints with current particle physics bounds we find that the contribution of a scalar field to the recently claimed discrepancy in the proton radius measured using electronic and muonic atoms is negligible.

We analyze the $B\to K_2^{*}(\to K\pi )l^{+}{l}^{-}$ (with $l=e$, $\mu$, $\tau$) decay in the standard model and two new physics scenarios: the vectorlike quark model and family nonuniversal $Z^{\prime }$ models. We derive the differential angular distributions using the recently calculated form factors in the perturbative QCD approach. Branching ratios, polarizations, forward-backward asymmetries, and transversity amplitudes are predicted, from which we find a promising prospective to observe this channel in future experiments. We update the constraints on effective Wilson coefficients and/or free parameters in these two new physics scenarios by making use of the $B\to K^{*}{l}^{+}{l}^{-}$ and $b\to s{l}^{+}{l}^{-}$ experimental data. Their impact on $B\to K_2^{*}{l}^{+}{l}^{-}$ is subsequently explored and, in particular, the zero-crossing point for the forward-backward asymmetry in these new physics scenarios can sizably deviate from the standard model. In addition we also generalize the analysis to a similar mode, $B_s\to f_2^{\prime }(1525)(\to K^{+}{K}^{-})l^{+}{l}^{-}$.

Recent works show that the original Kobayashi-Maskawa (KM) form of fermion mixing matrix exhibits some advantages, especially when discussing problems such as unitarity boomerangs and maximal $CP$ violation hypothesis. Therefore, the KM form of fermion mixing matrix is systematically studied in this paper. Starting with a general triminimal expansion of the KM matrix, we discuss the triminimal and Wolfenstein-like parametrizations with different basis matrices in detail. The quark-lepton complementarity relations play an important role in our discussions on describing quark mixing and lepton mixing in a unified way.

We consider the relationship between renormalizability and unitarity at a Lifshitz point in $d$ dimensions. We test tree unitarity for theories containing only scalars and fermions, and for pure gauge theory. In both cases, we find the requirement of weighted power-counting renormalizability is equivalent to that of tree unitarity.