We prove the strong sensitivity of the $gg\to H_1\to \gamma \gamma$ cross section at the Large Hadron Collider on the explicitly $CP$-violating phases of the minimal supersymmetric standard model, where $H_1$ is the lightest supersymmetric Higgs boson.

Very recently the BABAR collaboration has put forward a claim that the $X(3872)$ is not a $1^{++}$ resonance, as most of the phenomenological work on the subject was relying on, but rather a $2^{-+}$ one. We examine the consequences of this quantum number assignment for the solution of the $X(3872)$ puzzle. The molecular interpretation appears less likely, and the conventional charmonium interpretation should be reconsidered. There are several well-known difficulties with this interpretation, to which we add a new one: the production cross section at CDF is predicted to be much smaller than that observed. We also confirm, using a relativistic string model, the conclusion from potential models that the mass of the state is not consistent with expectations. In the tetraquark interpretation the $2^{-+}$ assignment implies a rich spectrum of partner states, although the $X(3872)$ may be among the few which are narrow enough to be observable.

Correlations of charged hadrons of $1<p_T<10\mathrm{Gev}/c$ with high $p_T$ direct photons and ${\pi }^0$ mesons in the range $5<p_T<15\mathrm{Gev}/c$ are used to study jet fragmentation in the $\gamma +\mathrm{\text{jet}}$ and dijet channels, respectively. The magnitude of the partonic transverse momentum, $k_T$, is obtained by comparing to a model incorporating a Gaussian $k_T$ smearing. The sensitivity of the associated charged hadron spectra to the underlying fragmentation function is tested and the data are compared to calculations using recent global fit results. The shape of the direct photon-associated hadron spectrum as well as its charge asymmetry are found to be consistent with a sample dominated by quark-gluon Compton scattering. No significant evidence of fragmentation photon correlated production is observed within experimental uncertainties.

In this note we point out that primordial black holes could be much shorter lived than usually assumed if there is a large hidden sector of particles that only interacts gravitationally with the particles of the standard model. The observation of the explosion of one of these black holes would severely constrain the energy scale at which gravity becomes strong.

We discuss the possible influence of a cosmic magnetic field on the macroscopic quantum tunneling process associated, in a cosmological context, to the decay of the “false vacuum.” We find a close analogy with the effects of an external magnetic field applied to a Josephson junction in the context of low-temperature/high-temperature superconducting devices.

We give a holographic realization of the recently proposed low-energy effective action describing a fractional topological insulator. In particular we verify that the surface of this hypothetical material supports a fractional quantum Hall current corresponding to half that of a Laughlin state.

In the present work, a family of Calabi-Yau manifolds with a local Hamiltonian Killing vector is described in terms of a nonlinear equation whose solutions determine the local form of the geometries. The main assumptions are that the complex (3, 0)-form is of the form $e^{ik}\overline{\Psi }$, where $\overline{\Psi }$ is preserved by the Killing vector, and that the space of the orbits of the Killing vector is, for fixed value of the momentum map coordinate, a complex 4-manifold, in such a way that the complex structure of the 4-manifold is part of the complex structure of the complex 3-fold. The family considered here include the ones considered in A. Fayyazuddin, Classical Quantum Gravity 24, 3151 (2007); O. P. Santillan, Classical Quantum Gravity 27, 155013 (2010); H. Lu, Y. Pang, and Z. Wang, Classical Quantum Gravity 27, 155018 (2010) as a particular case. We also present an explicit example with holonomy exactly SU(3) by use of the linearization introduced in A. Fayyazuddin, Classical Quantum Gravity 24, 3151 (2007), which was considered in the context of D6 branes wrapping a complex 1-cycle in a hyperkahler 2-fold.

We study the supersymmetric $\mathcal{N}=(2,2)$ Wess-Zumino model in two dimensions with the functional renormalization group. At leading order in the supercovariant derivative expansion we recover the nonrenormalization theorem which states that the superpotential has no running couplings. Beyond leading order the renormalization of the bare mass is caused by a momentum-dependent wave function renormalization. To deal with the partial differential equations we have developed a numerical toolbox called FlowPy. For weak couplings the quantum corrections to the bare mass found in lattice simulations are reproduced with high accuracy. But in the regime with intermediate couplings higher-order operators that are not constrained by the nonrenormalization theorem yield the dominating contribution to the renormalized mass.

For a 4D massive Dirac field in the background of arbitrary gauge fields, we show that the Dirac propagator and functional determinant are completely determined by knowledge of the corresponding quantities for just one of the chirality sectors of the second-order Dirac operator. This generalizes the related, previously known, statements in (anti)self-dual background gauge fields. The logarithms of the (renormalized) functional determinants from the two chirality sectors are shown to be different only by a term reflecting the integrated chiral anomaly.

We numerically evaluate the one-loop counterterms for the four-dimensional Wess-Zumino model formulated on the lattice using Ginsparg-Wilson fermions of the overlap (Neuberger) variety, together with an auxiliary fermion (plus superpartners), such that a lattice version of $U(1{)}_R$ symmetry is exactly preserved in the limit of vanishing bare mass. We confirm previous findings by other authors that at one loop there is no renormalization of the superpotential in the lattice theory, but that there is a mismatch in the wave-function renormalization of the auxiliary field. We study the range of the Dirac operator that results when the auxiliary fermion is integrated out, and show that localization does occur, but that it is less pronounced than the exponential localization of the overlap operator. We also present preliminary simulation results for this model, and outline a strategy for nonperturbative improvement of the lattice supercurrent through measurements of supersymmetry Ward identities. Related to this, some benchmarks for our graphics processing unit code are provided. Our simulation results find a nearly vanishing vacuum expectation value for the auxiliary field, consistent with approximate supersymmetry at weak coupling.

We use a WKB approximation to establish a relation between the wave front velocity in a strongly coupled theory and the local speed of light in a holographic dual, with our main focus put on systems with Lifshitz scaling with dynamical exponent $z$. We then use Einstein equations to relate the behavior of the local speed of light in the bulk with the null energy condition (NEC) for bulk matter, and we show that it is violated for Lifshitz backgrounds with $z<1$. We study signal propagation in the gravity dual and show that violations of the NEC are incompatible with causality in the strongly coupled theory, ruling out as holographic models Lifshitz backgrounds with $z<1$. We argue that causality violations in $z<1$ theories will show up in correlators as superluminal modes and confirm this for a particular example with $z=1/2$. Finally, as an application, we use $z<1$ solutions to uncover regions of the parameter space of curvature squared corrections to gravity where the NEC can be violated.

The characteristic formalism in numerical relativity, which has been developed to study gravitational waves, and the observer metric approach in observational cosmology both make use of coordinate systems based on null cones. In this paper, these coordinate systems are compared, and it is then demonstrated how characteristic numerical relativity can be used to investigate problems in observational cosmology. In a numerical experiment using the characteristic formalism, it is shown how the historical evolution of a Lemaître-Tolman-Bondi (LTB) universe compares to that of the $\Lambda$ cold dark matter ($\Lambda \mathrm{CDM}$) model given identical observational data on a local observer’s past null cone. It is demonstrated that even though observations at the current epoch can be interpreted as either LTB or $\Lambda \mathrm{CDM}$, these models have distinctly different histories, and at an earlier epoch, the LTB model will not represent a $\Lambda \mathrm{CDM}$ model.

Burrage, Davis, and Shaw [1] recently suggested exploiting the correlations between high and low energy luminosities of astrophysical objects to probe possible mixing between photons and axionlike particles (ALP) in magnetic field regions. They also presented evidence for the existence of ALP’s by analyzing the optical/UV and x-ray monochromatic luminosities of active galactic nuclei. We extend their work by using the monochromatic luminosities of 320 unobscured active galactic nuclei from the Sloan Digital Sky Survey/Xmm-Newton Quasar Survey [2] which allows the exploration of 18 different combinations of optical/UV and x-ray monochromatic luminosities. However, we do not find compelling evidence for the existence of ALPs. Moreover, it appears that the signal reported by Burrage et al. is more likely due to x-ray absorption rather than to photon-ALP oscillation.

Models that lead to a cosmological stiff fluid component, with a density ${\rho }_S$ that scales as $a^{-6}$, where $a$ is the scale factor, have been proposed recently in a variety of contexts. We calculate numerically the effect of such a stiff fluid on the primordial element abundances. Because the stiff fluid energy density decreases with the scale factor more rapidly than radiation, it produces a relatively larger change in the primordial helium-4 abundance than in the other element abundances, relative to the changes produced by an additional radiation component. We show that the helium-4 abundance varies linearly with the density of the stiff fluid at a fixed fiducial temperature. Taking ${\rho }_{S10}$ and ${\rho }_{R10}$ to be the stiff fluid energy density and the standard density in relativistic particles, respectively, at $T=10\mathrm{MeV}$, we find that the change in the primordial helium abundance is well-fit by $\Delta Y_p=0.00024({\rho }_{S10}/{\rho }_{R10})$. The changes in the helium-4 abundance produced by additional radiation or by a stiff fluid are identical when these two components have equal density at a “pivot temperature,” $T_{*}$, where we find $T_{*}=0.55\mathrm{MeV}$. Current estimates of the primordial ${}^4\mathrm{He}$ abundance give the constraint on a stiff fluid energy density of ${\rho }_{S10}/{\rho }_{R10}<30$.

We consider more than one pair of $SU(2{)}_L$ doublet Higgs supermultiplets in a generic supersymmetric extension of the standard model, and calculate their one-loop contributions to the soft mass insertions ${\delta }_{LL}$ etc. We find that, if large supersymmetry breaking in this sector is realized, the loop effects can give rise to large contributions to the soft mass insertions, meaning that they can generate large flavor-changing neutral currents and $CP$ violations. We apply our result to a recently proposed model based on the discrete $Q_6$ family group, and calculate the nondiagonal matrix element $M_{12}$ of the neutral meson systems. We focus our attention on the extra phases ${\varphi }_{d,s}^{\Delta }$ in $B_{d,s}$ mixing and flavor-specific $CP$ asymmetries $a_{sl}^{d,s}$ in neutral $B$ decays and obtain values that can be about 1 order of magnitude larger than the standard model predictions. Our final results are comparable with the recent experimental observations at D0 and CDF, but they are still about a factor of 5 smaller than the recently measured dimuon asymmetry from D0.

Using BlackHat in conjunction with SHERPA, we have computed next-to-leading order QCD predictions for a variety of distributions in $Z$,${\gamma }^{*}+1$, 2, 3-jet production at the Tevatron, where the $Z$ boson or off-shell photon decays into an electron-positron pair. We find good agreement between the next-to-leading order results for jet $p_T$ distributions and measurements by CDF and D0. We also present jet-production ratios, or probabilities of finding one additional jet. As a function of vector-boson $p_T$, the ratios have distinctive features which we describe in terms of a simple model capturing leading logarithms and phase-space and parton-distribution-function suppression.

The tetraquark states with diquark–anti-diquark configuration have been studied in the flux-tube model, in which the multibody confinement is used. In this model approach, the states $Y(2175)$, $f_0(600)$, $f_0(980)$, and $X(1576)$ can be assigned as tetraquark states. They are color confinement resonances with three-dimension structure. This study suggests that the multibody confinement should be employed in the quark model study of multiquark states instead of the additive two-body confinement.

We give some evidences of the Alday-Gaiotto-Tachikawa-Wyllard relation between $SU(3)$ quiver gauge theories and $A_2$ Toda theory. In particular, we derive the explicit form of 5-point correlation functions in the lower orders and confirm the agreement with Nekrasov’s partition function for $SU(3)\times SU(3)$ quiver gauge theory. The algorithm to derive the correlation functions can be applied to a general $n$-point function in $A_2$ Toda theory, which will be useful to establish the relation for more generic quivers. Partial analysis is also given for the $SU(3)\times SU(2)$ case, and we comment on some technical issues that need clarification before establishing the relation.

Projected spin network states are the canonical basis of quantum states of geometry for the recent EPRL-FK spinfoam models for quantum gravity introduced by Engle-Pereira-Rovelli-Livine and Freidel-Krasnov. They are functionals of both the Lorentz connection and the time-normal field. We analyze in detail the map from these projected spin networks to the standard SU(2) spin networks of loop quantum gravity. We show that this map is not one to one and that the corresponding ambiguity is parameterized by the Immirzi parameter. We conclude with a comparison of the scalar products between projected spin networks and SU(2) spin network states.

The Sachs equations governing the evolution of the optical matrix of geodetic WANDs (Weyl aligned null directions) are explicitly solved in $n$ dimensions in several cases which are of interest in potential applications. This is then used to study Einstein spacetimes of type III and N in the higher dimensional Newman-Penrose formalism, considering both Kundt and expanding (possibly twisting) solutions. In particular, the general dependence of the metric and of the Weyl tensor on an affine parameter $r$ is obtained in a closed form. This allows us to characterize the peeling behavior of the Weyl “physical” components for large values of $r$, and thus to discuss, e.g., how the presence of twist affects polarization modes, and qualitative differences between four and higher dimensions. Further, the $r$ dependence of certain nonzero scalar curvature invariants of expanding spacetimes is used to demonstrate that curvature singularities may generically be present. As an illustration, several explicit type N/III spacetimes that solve Einstein’s vacuum equations (with a possible cosmological constant) in higher dimensions are finally presented.