We propose a simple field theory reproducing MOND phenomenology at galaxy scale, while predicting negligible deviations from general relativity at small scales thanks to an extended Vainshtein (“$k$-mouflage”) mechanism induced by a covariant Galileon-type Lagrangian. The model passes all solar-system tests, including those of local Lorentz invariance, and its anomalous forces in binary pulsars are vanishingly small. The large-distance behavior is obtained as in Bekenstein’s tensor-vector-scalar model, but with several simplifications. In particular, no fine-tuned function is needed to interpolate between the MOND and Newtonian regimes, and the vector field may be nondynamical. The field equations depend on second (and lower) derivatives, and thus avoid the generic Ostrogradski instabilities. We also underline why the proposed model is particularly efficient within the class of covariant Galileons.

We explore some ways of minimally modifying the neutrino mixing matrix from tribimaximal, characterized by introducing at most one mixing angle and a $CP$ violating phase thus extending our earlier work. One minimal modification, motivated to some extent by group theoretic considerations, is a simple case with the elements $V_{\alpha 2}$ of the second column in the mixing matrix equal to $1/\sqrt{3}$. Modifications by keeping one of the columns or one of the rows unchanged from tribimaximal mixing all belong to the class of minimal modification. Some of the cases have interesting experimentally testable consequences. In particular, the T2K and MINOS collaborations have recently reported indications of a nonzero ${\theta }_{13}$. For the cases we consider, the new data sharply constrain the $CP$ violating phase angle $\delta$, with $\delta$ close to 0 (in some cases) and $\pi$ disfavored.

We present a direct measurement of the mass difference between top and antitop quarks ($\Delta m$) in $\mathrm{\text{lepton}}+\mathrm{\text{jets}}$ $t\overline{t}$ final states using the “matrix element” method. The purity of the $\mathrm{\text{lepton}}+\mathrm{\text{jets}}$ sample is enhanced for $t\overline{t}$ events by identifying at least one of the jets as originating from a $b$ quark. The analyzed data correspond to $3.6{\mathrm{fb}}^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ acquired by D0 in Run II of the Fermilab Tevatron Collider. The combination of the $e+\mathrm{\text{jets}}$ and $\mu +\mathrm{\text{jets}}$ channels yields $\Delta m=0.8\pm 1.8(\mathrm{stat})\pm 0.5(\mathrm{syst})\mathrm{GeV}$, which is in agreement with the standard model expectation of no mass difference.

The distribution of linearly polarized gluons inside a large nucleus is studied in the framework of the color glass condensate. We find that the Weizsäcker-Williams distribution saturates the positivity bound at large transverse momenta and is suppressed at small transverse momenta, whereas the dipole distribution saturates the bound for any value of the transverse momentum. We also discuss processes in which both distributions of linearly polarized gluons can be probed.

The results presented in this paper differ from our previous unsuccessful attempt to predict the rapidity distribution at $W=7\mathrm{TeV}$. The original version of our model only summed a particular class of Pomeron diagrams (enhanced diagrams). We believe that this was the reason for our failure to describe the 7 TeV inclusive LHC data. We have developed a new approach that also includes the summation of the semienhanced diagrams. This contribution is essential for a successful description of the inclusive distributions, which is presented here.

We investigate finite energy solutions of the Einstein–Yang-Mills–Chern-Simons system in odd spacetime dimensions, $D=2n+1$, with $n>1$. Our configurations are static and spherically symmetric, approaching at infinity a Minkowski spacetime background. In contrast with the Abelian case, the contribution of the Chern-Simons term is nontrivial already in the static, spherically symmetric limit. Both globally regular, particlelike solutions and black holes are constructed numerically for several values of $D$. These solutions carry a nonzero electric charge and have finite mass. For globally regular solutions, the value of the electric charge is fixed by the Chern-Simons coupling constant. The black holes can be thought of as nonlinear superpositions of Reissner-Nordström and non-Abelian configurations. A systematic discussion of the solutions is given for $D=5$, in which case the Reissner-Nordström black hole becomes unstable and develops non-Abelian hair. We show that some of these non-Abelian configurations are stable under linear, spherically symmetric perturbations. A detailed discussion of an exact $D=5$ solution describing extremal black holes and solitons is also provided.

We investigate the pair creation of noncommutative black holes in a background with a positive cosmological constant. As a first step we derive the noncommutative geometry inspired Schwarzschild–de Sitter solution. By varying the mass and the cosmological constant parameters, we find several spacetimes compatible with the new solution: positive-mass spacetimes admit one cosmological horizon and two, one, or no black hole horizons, while negative-mass spacetimes have just a cosmological horizon. These new black holes share the properties of the corresponding asymptotically flat solutions, including the nonsingular core and thermodynamic stability in the final phase of the evaporation. As a second step we determine the action which generates the matter sector of gravitational field equations and we construct instantons describing the pair production of black holes and the other admissible topologies. As a result we find that for current values of the cosmological constant the de Sitter background is quantum mechanically stable according to experience. However, positive-mass noncommutative black holes and solitons would have plentifully been produced during inflationary times for Planckian values of the cosmological constant. As a special result we find that, in these early epochs of the Universe, Planck size black holes production would have been largely disfavored. We also find a potential instability for production of negative-mass solitons.

We derive a gauge-invariant low-energy effective model of the Yang-Mills theory. We find that the effective gluon propagator belongs to the Gribov-Stingl type and agrees with it when a mass term that breaks nilpotency of the BRST symmetry is included. We show that the effective model with gluon propagator of the Gribov-Stingl type exhibits both quark and gluon confinement: the Wilson loop average has the area law and the Schwinger function violates reflection positivity. However, we argue that both quark and gluon confinement can be obtained even in the absence of such a mass term.

We investigate the prospects of supersymmetry searches at the LHC with 7 TeV energy. A new set of selection cuts is proposed based on event shapes to control backgrounds. Our preliminary studies show that it is possible to minimize backgrounds to a significantly low level and a conservative estimate suggests that the mass reach can be extended to $\sim 1.1\mathrm{TeV}$ for luminosity $\mathcal{L}=1{\mathrm{fb}}^{-1}$ with a reasonable signal-to-background ratio.

Considering recently developed hard thermal loop perturbation theory that takes into account the effect of the variation of the external field through the fluctuations of a conserved quantity we calculate the temporal component of the Euclidean correlation function in the vector channel. The results are found to be in good agreement with the very recent results obtained within the quenched approximation of QCD and small values of the quark mass ($\sim 0.1T$) on improved lattices of size ${128}^3\times N_{\tau }$ at ($N_{\tau }=40$, $T=1.2T_C$), ($N_{\tau }=48$, $T=1.45T_C$), and ($N_{\tau }=16$, $T=2.98T_C$), where $N_{\tau }$ is the temporal extent of the lattice. This suggests that the results from lattice QCD and hard thermal loop perturbation theory are in close proximity for a quantity associated with the conserved density fluctuation.

We use holography to study the spontaneous condensation of a neutral order parameter in a $(2+1)$-dimensional field theory at zero temperature and finite density, dual to the electron-star background of Hartnoll and Tavanfar. An appealing feature of this field theory is the emergence of an IR Lifshitz fixed point with a finite dynamical critical exponent $z$, which is due to the strong interaction between critical bosonic degrees of freedom and a finite density of fermions (metallic quantum criticality). We show that under some circumstances the electron-star background develops a neutral scalar hair whose holographic interpretation is that the boundary field theory undergoes a quantum phase transition, with a Berezinski-Kosterlitz-Thouless character, to a phase with a neutral order parameter. Including the backreaction of the bulk neutral scalar on the background, we argue that the two phases across the quantum critical point have different $z$, a novelty that exists in certain quantum phase transitions in condensed matter systems. We also analyze the system at finite temperature and find that the phase transition becomes, as expected, second order. Embedding the neutral scalar into a higher form, a variety of interesting phases could potentially be realized for the boundary field theory. Examples which are of particular interest to condensed matter physics include an antiferromagnetic phase where a vector condenses and breaks the spin symmetry, a quadrupole nematic phase which involves the condensation of a symmetric traceless tensor breaking rotational symmetry, or different phases of a system with competing order parameters.

We use soft collinear effective theory (SCET) to analyze the transverse momentum broadening, or diffusion in transverse momentum space, of an energetic parton propagating through quark-gluon plasma. Since we neglect the radiation of gluons from the energetic parton, we can only discuss momentum broadening, not parton energy loss. The interaction responsible for momentum broadening in the absence of radiation is that between the energetic (collinear) parton and the Glauber modes of the gluon fields in the medium. We derive the effective Lagrangian for this interaction, and we show that the probability for picking up transverse momentum $k_{\perp }$ is given by the Fourier transform of the expectation value of two transversely separated lightlike path-ordered Wilson lines. This yields a field-theoretical definition of the jet-quenching parameter $\widehat{q}$, and shows that this can be interpreted as a diffusion constant. We close by revisiting the calculation of $\widehat{q}$ for the strongly coupled plasma of $\mathcal{N}=4$ SYM theory, showing that previous calculations need some modifications that make them more straightforward and do not change the result.

The effect of an applied magnetic field in the crossover from Bose-Einstein condensate (BEC) to Bardeen-Cooper-Schrieffer (BCS) pairing regimes is investigated. We use a model of relativistic fermions and bosons inspired by those previously used in the context of cold fermionic atoms and in the magnetic-color-flavor-locking phase of color superconductivity. It turns out that, as with cold atom systems, an applied magnetic field can also tune the BCS-BEC crossover in the relativistic case. We find that no matter what the initial state is at $B=0$, for large enough magnetic fields the system always settles into a pure BCS regime. In contrast to the atomic case, the magnetic field tuning of the crossover in the relativistic system is not connected to a Feshbach resonance, but to the relative numbers of Landau levels with either BEC or BCS type of dispersion relations that are occupied at each magnetic field strength.

The QCD string breaking due to quark pair creation in the vacuum confining field, possibly accompanied by vector, scalar, or Nambu-Goldstone bosons, is studied nonperturbatively. The scalar light-pair creation vertex occurs due to chiral symmetry breaking and has a confining form, which is computed explicitly together with subleading vector contributions. Dependence on light quark mass and flavor is specifically studied. The dominant scalar term is in good agreement with the ${}^{3}P_0$ model and experimental data.

In this article we establish the relationship between fermionic $T$ duality and momenta noncommutativity. This is an extension of a known relation between bosonic $T$ duality and coordinate noncommutativity. The case of an open string propagating in the background of the type IIB superstring theory has been considered. We perform $T$ duality with respect to the fermionic variables instead to the bosonic ones. We also choose Dirichlet boundary conditions at the string end points, which lead to the momenta noncommutativity, instead Neumann ones which lead to the coordinate noncommutativity. Finally, we establish the main result of the article, that momenta noncommutativity parameters are just fermionic $T$-dual fields.

A general method is presented for estimating the uncertainty in hybrid models of gravitational waveforms from binary black-hole systems with arbitrary physical parameters, and thence the highest allowable initial orbital frequency for a numerical-relativity simulation such that the combined analytical and numerical waveform meets some minimum desired accuracy. The key strength of this estimate is that no prior numerical simulation in the relevant region of parameter space is needed, which means that these techniques can be used to direct future work. The method is demonstrated for a selection of extreme physical parameters. It is shown that optimal initial orbital frequencies depend roughly linearly on the mass of the binary, and therefore useful accuracy criteria must depend explicitly on the mass. The results indicate that accurate estimation of the parameters of stellar-mass black-hole binaries in Advanced LIGO data or calibration of waveforms for detection will require much longer numerical simulations than are currently available, or more accurate post-Newtonian approximations—or both—especially for comparable-mass systems with high spin.

Various prescriptions proposed in the literature to attain the polymeric quantization of a homogeneous and isotropic flat spacetime coupled to a massless scalar field are carefully analyzed in order to discuss their differences. A detailed numerical analysis confirms that, for states which are not deep in the quantum realm, the expectation values and dispersions of some natural observables of interest in cosmology are qualitatively the same for all the considered prescriptions. On the contrary, the amplitude of the wave functions of those states differs considerably at the bounce epoch for these prescriptions. This difference cannot be absorbed by a change of representation. Finally, the prescriptions with simpler superselection sectors are clearly more efficient from the numerical point of view.

Gauge theories formulated in a space-time manifold that includes compact extra dimensions can show a nontrivial gauge structure. Depending on whether the gauge parameters propagate or not in the extra dimensions, two different Kaluza-Klein theories can arise when the extra dimensions are compactified. A comparison between these two possibilities, in the context of a five-dimensional theory, is presented from both the theoretical and phenomenological viewpoints. The phenomenological implications of these theories are contrasted by discussing the one-loop decay of the Higgs boson into two photons. It is shown that the amplitude for this decay differs substantially from one approach to the other and that such a difference is intimately related to gauge invariance.

We study technicolor models in which all of the technifermions are color-singlets, focusing on the case in these fermions transform according to the fundamental representation of the technicolor gauge group. Our analysis includes a derivation of restrictions on the weak hypercharge assignments for the technifermions and additional color-singlet, technisinglet fermions arising from the necessity of avoiding stable bound states with exotic electric charges. Precision electroweak constraints on these models are also discussed. We determine some general properties of extended technicolor theories containing these technicolor sectors.

Recently observed anomalies in the $B_s\to J/\psi \varphi$ decay and the like-sign dimuon asymmetry $A_{sl}^b$ hint at possible new physics (NP) in the $B_s-{\overline{B}}_s$ mixing. We parameterize the NP with four model-independent quantities: the magnitudes and phases of the dispersive part $M_{12}$ and the absorptive part ${\Gamma }_{12}$ of the NP contribution to the effective Hamiltonian. We constrain these parameters using the four observables $\Delta M_s$, $\Delta {\Gamma }_s$, the mixing phase ${\beta }_s^{J/\psi \varphi }$, and $A_{sl}^b$. Our quantitative fit indicates that the NP should contribute a significant dispersive as well as absorptive part. In fact, models that do not contribute a new absorptive part are disfavored at more than 99% confidence level. We extend this formalism to include $CPT$ violation, and show that $CPT$ violation by itself, or even in presence of $CPT$-conserving new physics without an absorptive part, helps only marginally in the simultaneous resolution of these anomalies. The NP absorptive contribution to $B_s-{\overline{B}}_s$ mixing therefore seems to be essential, and would imply a large branching fraction for channels like $B_s\to {\tau }^{+}{\tau }^{-}$.