In the framework of relativistic positioning systems in Minkowski space-time, the determination of the inertial coordinates of a user involves the bifurcation problem (which is the indeterminate location of a pair of different events receiving the same emission coordinates). To solve it, in addition to the user emission coordinates and the emitter positions in inertial coordinates, it may happen that the user needs to know independently the orientation of its emission coordinates. Assuming that the user may observe the relative positions of the four emitters on its celestial sphere, an observational rule to determine this orientation is presented. The bifurcation problem is thus solved by applying this observational rule, and consequently, all of the parameters in the general expression of the coordinate transformation from emission coordinates to inertial ones may be computed from the data received by the user of the relativistic positioning system.

We present a Chern-Simons-like action for the general massive gravity model propagating two spin-2 modes with independent masses in three spacetime dimensions (3D), and we use it to find a simple Hamiltonian form of this model. The number of local degrees of freedom, determined by the dimension of the physical phase space, agrees with a linearized analysis except in some limits, in particular that yielding topologically new massive gravity, which therefore suffers from a linearization instability.

We study a retarded potential solution of a massless scalar field in curved space-time. In a special ansatz for a particle at rest whose magnitude of the (scalar) charge is changing with time, we found an exact analytic solution. The solution indicates that the phase velocity of the retarded potential of a nonmoving scalar charge is position-dependent and may easily be greater than the speed of light at a given point. In the case of the Schwarzschild space-time, at the horizon, the phase velocity becomes infinitely faster than the coordinate speed of light at that point. Superluminal phase velocity is a relatively common phenomenon, with the phase velocity of the massive Klein-Gordon field as the best known example. We discuss why it is possible to have modes with superluminal phase velocity even for a massless field.

We derive general covariant expressions for the six independent observable modes of distortion of ideal standard rulers in a perturbed Friedmann-Robertson-Walker spacetime. Our expressions are gauge invariant and valid on the full sky. These six modes are most naturally classified in terms of their rotational properties on the sphere, yielding two scalars, two vector (spin-1), and two tensor (spin-2) components. One scalar corresponds to the magnification, while the spin-2 components correspond to the shear. The vector components allow for a polar/axial decomposition analogous to the $E/B$ decomposition for the shear. Scalar modes do not contribute to the axial ($B$-)vector, opening a new avenue to probing tensor modes. Our results apply, but are not limited to, the distortion of correlation functions (of the cosmic microwave background, 21-cm emission, or galaxies) as well as to weak lensing shear and magnification, all of which can be seen as methods relying on “standard rulers.”

We present an update to the search for a nontrivial topology of the Universe by searching for matching circle pairs in the cosmic microwave background [N. J. Cornish et al. Phys. Rev. Lett. 92, 201 302 (2004)] using the WMAP 7-year data release. We extend the existing bounds to encompass a wider range of possible topologies by searching for matching circle pairs with opening angles $10°\le \alpha \le 90°$ and separation angles $11°\le \theta \le 180°$. The extended search reveals two small anomalous regions in the cosmic microwave background sky. Numerous pairs of well-matched circles are found where both circles pass through one or the other of those regions. As this is not the signature of any known manifold, but is a likely consequence of contamination in those sky regions, we repeat the search excluding circle pairs where both pass through either of the two regions. We then find no statistically significant pairs of matched circles, and so no hints of a nontrivial topology. The absence of matched circles increases the lower limit on the length of the shortest closed null geodesic that self-intersects at our location in the Universe (equivalently the injectivity radius at our location) to 98.5% of the diameter of the last scattering surface or approximately 26 Gpc. It extends the limit to any manifolds in which the intersecting arcs of said geodesic form an angle greater than 10°.

We demonstrate the feasibility to generate surrogates by Fourier-based methods for an incomplete data set. This is performed for the case of a cosmic microwave background analysis, where astrophysical foreground emission, mainly present in the Galactic plane, is a major challenge. The shuffling of the Fourier phases for generating surrogates is now enabled by transforming the spherical harmonics into a new set of basis functions that are orthonormal on the cut sky. The results show that non-Gaussianities and hemispherical asymmetries in the cosmic microwave background as identified in several former investigations, can still be detected even when the complete Galactic plane ($|b|<30°$) is removed. We conclude that the Galactic plane cannot be the dominant source for these anomalies. The results point towards a violation of statistical isotropy.

We extend our analysis [S. S. Agaev, V. M. Braun, N. Offen, and F. A. Porker, Phys. Rev. D 83, 054020 (2011)] of the ${\pi }^0{\gamma }^{*}\gamma$ form factor by including a comparison with the new Belle data [S. Uehara et al. (Belle Collaboration), arXiv:1205.3249]. The necessity of new precision measurements in a broad interval of momentum transfers is emphasized.

A feature of the inert doublet model (IDM) is to provide a dark matter candidate together with an alteration of both direct and indirect collider constraints that allow for a heavy Higgs boson. We study the IDM in light of recent results from Higgs searches at the Large Hadron Collider (LHC) in combination with dark matter direct detection limits from the XENON experiment. We ask under what conditions the IDM can still accommodate a heavy Higgs boson. We find that IDM scenarios with a Higgs boson in the mass range 160–600 GeV are ruled out only when all experimental constraints are combined. For models explaining only a fraction of the dark matter the limits are weakened, and IDMs with a heavy Higgs are allowed. We discuss the prospects for future detection of such IDM scenarios in the four-lepton plus missing energy channel at the LHC. This signal can show up in the first year of running at $\sqrt{s}=14\mathrm{TeV}$, and we present detector-level studies for a few benchmark models.

In this work, we deal with the critical behavior of the bulk viscosity in the linear sigma model ($\mathrm{L}\sigma \mathrm{M}$) as an example of a system which can be treated by using different techniques. Starting from the Boltzmann-Uehling-Uhlenbeck equation, we compute the bulk viscosity over entropy density of the $\mathrm{L}\sigma \mathrm{M}$ in the large-$N$ limit. We search for a possible maximum of $\zeta /s$ at the critical temperature of the chiral phase transition. The information about this critical temperature, as well as the effective masses, is obtained from the effective potential. We find that the expected maximum (as a measure of the conformality loss) is absent in the large-$N$ limit in agreement with other models in the same limit. However, this maximum appears when, instead of the large-$N$ limit, the Hartree approximation within the Cornwall-Jackiw-Tomboulis formalism is used. Nevertheless, this last approach to the $\mathrm{L}\sigma \mathrm{M}$ does not give rise to the Goldstone theorem and also predicts a first-order phase transition instead of the expected second-order one. Therefore, both the large-$N$ limit and the Hartree approximations, should be considered relevant and informative for the study of the critical behavior of the bulk viscosity in the $\mathrm{L}\sigma \mathrm{M}$.

Measurements are presented of the properties of high transverse momentum jets, produced in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=7\mathrm{TeV}$. The data correspond to an integrated luminosity of $35{\mathrm{pb}}^{-1}$ and were collected with the ATLAS detector in 2010. Jet mass, width, eccentricity, planar flow and angularity are measured for jets reconstructed using the anti-$k_t$ algorithm with distance parameters $R=0.6$ and 1.0, with transverse momentum $p_T>300\mathrm{GeV}$ and pseudorapidity $|\eta |<2$. The measurements are compared to the expectations of Monte Carlo generators that match leading-logarithmic parton showers to leading-order, or next-to-leading-order, matrix elements. The generators describe the general features of the jets, although discrepancies are observed in some distributions.

This paper presents techniques and results for simulations of unequal-mass, nonspinning binary black holes with pseudospectral methods. Specifically, we develop an efficient root-finding procedure to ensure the black hole initial data have the desired masses and spins; we extend the dual coordinate frame method and eccentricity removal to asymmetric binaries. Furthermore, we describe techniques to simulate mergers of unequal-mass black holes. The second part of the paper presents numerical simulations of nonspinning binary black holes with mass ratios 2, 3, 4, and 6, covering between 15 and 22 orbits, merger and ringdown. We discuss the accuracy of these simulations, the evolution of the (initially zero) black hole spins, and the remnant black hole properties.

Top partners from a new strong sector can be discovered soon, at the 8 TeV LHC, by analyzing their single production, which exhibits a large enhancement in the cross section compared to the analogous productions of bottom partners and exotic quarks. We analyze the subsequent decay of the top partners into a 125 GeV Higgs. This channel proves to be very promising for both the discovery of top partners and a test of the Higgs sector. For a reference value ${\lambda }_{\tilde{T}}=3$ of the Higgs coupling to the top partner, we could have a discovery (observation) at the 8 TeV LHC, with $30{\mathrm{fb}}^{-1}$, for top partner masses up to 760 (890) GeV. If the LHC and Tevatron excesses near 125 GeV are really due to a composite Higgs, naturalness arguments demand top partners below $\sim 1\mathrm{TeV}$. Our results highlight thus that the 8 TeV LHC already has a large sensitivity on probing the composite Higgs hypothesis. The LHC reach is even wider at $\sqrt{s}=14\mathrm{TeV}$. With ${\lambda }_{\tilde{T}}=3$ the LHC with $100{\mathrm{fb}}^{-1}$ can observe (at $5\sigma$) a Higgs from a top partner decay for masses of this latter up to $\simeq 1450\mathrm{GeV}$. In the case that the top partner is as light as $\simeq 500\mathrm{GeV}$, the 14 TeV LHC would be sensitive to the measure of the ${\lambda }_{\tilde{T}}$ coupling in basically the full range ${\lambda }_{\tilde{T}}>1$ predicted by the theory.

In this work, we adopt the simplest model that spontaneously breaks supersymmetry, namely, the minimal O’Raifeartaigh model. The effective potential is computed in the framework of the linear delta expansion approach up to the order ${\delta }^2$, conjugated with superspace and supergraph techniques. The latter can be duly mastered even if supersymmetry is no longer exact, and the efficacy of the superfield approach in connection with the linear delta expansion procedure is confirmed according to our investigation. That opens up a way for a semi-nonperturbative superspace computation that allows us to deal with spontaneously broken supersymmetric models and encourages us to go further and apply this treatment to the minimal supersymmetric Standard Model precision tests.

In the context of departures from special relativity written as a momentum power expansion in the inverse of an ultraviolet energy scale $M$, we derive the constraints that the relativity principle imposes between coefficients of a deformed (but rotational invariant) composition law, dispersion relation, and transformation laws, at first order in the power expansion. In particular, we find that at that order the consistency of a modification of the energy-momentum composition law fixes the modification in the dispersion relation. We therefore obtain the most generic modification of special relativity which is rotational invariant and that preserves the relativity principle at leading order in $1/M$.

The Campanelli-Lousto solutions of Brans-Dicke theory, usually reported as black holes, are reconsidered and shown to describe, according to the values of a parameter, wormholes or naked singularities. The veiled Schwarzschild metric recently used as an example to discuss conformal frames and their equivalence corresponds to a special case of the Campanelli-Lousto metric. The conformal cousins of these solutions, and of the Riegert black hole solution of conformally invariant Weyl theory, are analyzed, leading to a word of caution when physically interpreting spacetimes generated via conformal transformations from known seed solutions.

If two particles collide near the horizon of a rotating extremal black hole, under certain conditions the energy $E_{\mathrm{c}.\mathrm{m}.}$ in the center-of-mass frame can grow without limit (the so-called Banados-Silk-West effect). We consider collisions that produce two other particles. We show that for a generic dirty (surrounded by matter) black hole, there exist upper bounds on the energy and mass of product particles which can be detected at infinity. As a result, the positive energy gain is possible but is quite modest. It mainly depends on two numbers in which near-horizon behavior of the metric is encoded. The obtained results suggest astrophysical limits on the possibility of observation of the products of the collisional Banados-Silk-West effect. These results are consistent with recent calculations for the Kerr metric, extending them to generic dirty black holes. It is shown that for dirty black holes there are types of scenarios of energy extraction impossible in the Kerr case.

We study the radiative pion decay ${\pi }^{+}\to e^{+}{\nu }_e\gamma$ within nonlocal chiral quark models that include wave function renormalization. In this framework we analyze the momentum dependence of the vector form factor $F_V(q^2)$ and the slope of the axial-vector form factor $F_A(q^2)$ at threshold. Our results are compared with available experimental information and with the predictions given by the Nambu–Jona-Lasinio model. In addition we calculate the low energy constants ${\ell }_5$ and ${\ell }_6$, comparing our results with the values obtained in chiral perturbation theory.

We study the oscillations of a uniform longitudinal chromoelectric field in a dynamically evolving momentum-space anisotropic background in the weak field limit. Evolution equations for the background are derived by taking moments of the Boltzmann equation in two cases: (i) a fixed relaxation time and (ii) a relaxation time which is proportional to the local inverse-transverse momentum scale of the plasma. The second case allows us to reproduce 2nd-order viscous hydrodynamical dynamics in the limit of small shear viscosity-to-entropy ratio. We then linearize the Boltzmann-Vlasov equation in a dynamically evolving background and obtain an integrodifferential evolution equation for the chromoelectric field. We present numerical solutions to this integrodifferential equation for a variety of different initial conditions and shear viscosity-to-entropy density ratios. The dynamical equations obtained are novel in that they include a nontrivial time-dependent momentum-space anisotropic background and the effect of collisional damping for the first time.

We consider the factorization of one-loop amplitudes at complex kinematic points. By determining the terms that are absent for real kinematics, we can construct a recursive ansatz for the purely rational pieces of one-loop amplitudes in massless theories. We illustrate this method by verifying the Bern et al. $n$-point ansatze for the single-minus one-loop amplitudes in Yang-Mills theory and by constructing the scalar contribution to the one-loop five-graviton maximal-helicity-violating scattering amplitude.