A general diffeomorphism-invariant SU(2) gauge theory is a gravity theory with two propagating polarizations of the graviton. We develop this description of gravity, in particular, for future applications to the perturbative quantization. Thus, the linearized theory, gauge symmetries, and gauge fixing are discussed in detail, and the propagator is obtained. The propagator takes a simple form of that of Yang-Mills theory with an additional projector on diffeomorphism-equivalence classes of connections inserted. In our approach the gravitational perturbation theory takes a rather unusual form in that the Planck length is no longer fundamental.

New massive gravity provides a nonlinear extension of the Fierz-Pauli mass for gravitons in $2+1$ dimensions. Here we construct a Weyl-invariant version of this theory. When the Weyl symmetry is broken, the graviton gets a mass in analogy with the Higgs mechanism. In (anti)-de Sitter backgrounds, the symmetry can be broken spontaneously, but in flat backgrounds radiative corrections, at the two-loop level, break the Weyl symmetry à la Coleman-Weinberg mechanism. We also construct the Weyl-invariant extensions of some other higher-derivative models, such as the Gauss-Bonnet theory (which reduces to the Maxwell theory in three dimensions) and the Born-Infeld type gravities.

We examine the electromagnetic and gravitational wave (GW) signatures of stellar-mass compact objects (COs) spiraling into a supermassive black hole (extreme mass-ratio inspirals), embedded in a thin, radiation-pressure dominated, accretion disk. At large separations, the tidal effect of the secondary CO clears a gap. We derive the conditions necessary for gap opening in a radiation-pressure dominated disk and show that the gap refills during the late GW-driven phase of the inspiral, leading to a sudden electromagnetic brightening of the source. The accretion disk leaves an imprint on the GW through its angular momentum exchange with the binary, the mass increase of the binary members due to accretion, and its gravity. We compute the disk-modified GWs both in an analytical Newtonian approximation and in a numerical effective-one-body approach. We find that disk-induced migration provides the dominant perturbation to the inspiral, with weaker effects from the mass accretion onto the CO and hydrodynamic drag. Depending on whether a gap is present, the perturbation of the GW phase is between 10 and 1000 rad per year, detectable with the future Laser Interferometer Space Antenna at high significance. The perturbation is significant for disk models with an effective viscosity proportional to gas pressure but much less so if proportional to the total pressure. The Fourier transform of the disk-modified GW in the stationary phase approximation is sensitive to disk parameters with a frequency trend different from post-Newtonian vacuum corrections. Our results suggest that observations of extreme mass-ratio inspirals may place new sensitive constraints on the physics of accretion disks.

The finite-temperature effective potential customarily employed to describe the physics of cosmological phase transitions often relies on specific gauge choices, and is manifestly not gauge invariant at finite order in its perturbative expansion. As a result, quantities relevant for the calculation of the spectrum of stochastic gravity waves resulting from bubble collisions in first-order phase transitions are also not gauge invariant. We assess the quantitative impact of this gauge dependence on key quantities entering predictions for gravity waves from first-order cosmological phase transitions. We resort to a simple Abelian Higgs model, and discuss the case of $R_{\xi }$ gauges. By comparing with results obtained using a gauge-invariant Hamiltonian formalism, we show that the choice of gauge can have a dramatic effect on theoretical predictions for the normalization and shape of the expected gravity wave spectrum. We also analyze the impact of resumming higher-order contributions as needed to maintain the validity of the perturbative expansion, and show that doing so can suppress the amplitude of the spectrum by an order of magnitude or more. We comment on open issues and possible strategies for carrying out “daisy resummed” gauge-invariant computations in non-Abelian models for which a gauge-invariant Hamiltonian formalism is not presently available.

We present an assessment of the standard model expectations for the branching ratio of the isotopic spin and G-parity violating decay $\tau \to {\eta }^{\prime }\pi {\nu }_{\tau }$. This estimate is based on a vector and scalar meson dominance parametrization of the relevant form factors, that explicitly accounts for ${\pi }^0-\eta -{\eta }^{\prime }$ mixing. The numerical results obtained in this framework indicate a branching ratio 1 order of magnitude (or more) below the current experimental limit and suggest the possibility of evidencing some novel interaction in high statistics studies of this decay.

We investigate the prospects for the discovery of massive color-octet vector bosons at the CERN Large Hadron Collider with $\sqrt{s}=14\mathrm{TeV}$. A phenomenological Lagrangian is adopted to evaluate the cross section of a pair of colored vector bosons (colorons, $\tilde{\rho }$) decaying into four colored scalar resonances (hyper-pions, $\tilde{\pi }$), which then decay into eight gluons. We include the dominant physics background from the production of $8g$, $7g1q$, $6g2q$, and $5g3q$, and determine the masses of $\tilde{\pi }$ and $\tilde{\rho }$ where discovery is possible. For example, we find that a $5\sigma$ signal can be established for $M_{\tilde{\pi }}\lesssim 495\mathrm{GeV}$ ($M_{\tilde{\rho }}\lesssim 1650\mathrm{GeV}$). More generally we give the reach of this process for a selection of possible cuts and integrated luminosities.

The mass $m_{K^{*}}$ and vector coupling $f_{K^{*}}$ of the $K^{*}$ meson, as well as the ratio of the tensor to vector couplings $\frac{f_T}{f_V}{|}_{K^{*}}$, are computed in lattice QCD. Our simulations are performed in a partially quenched setup, with two dynamical (sea) Wilson quark flavors, having a maximally twisted mass term. Valence quarks are either of the standard or the Osterwalder-Seiler maximally twisted variety. Results obtained at three values of the lattice spacing are extrapolated to the continuum, giving $m_{K^{*}}=981(33)\mathrm{MeV}$, $f_{K^{*}}=240(18)\mathrm{MeV}$, and $\frac{f_T(2\mathrm{GeV})}{f_V}{|}_{K^{*}}=0.704(41)$.

We argue that a relatively light massive gluon with mass $\lesssim 1\mathrm{TeV}$, small purely axial couplings to light quarks and sizable vector and axial couplings to the top quark can reproduce the large forward-backward asymmetry observed at the Tevatron without conflicting with the $t\overline{t}$ and the dijet invariant-mass distributions measured at the Tevatron and the LHC. We show that realistic Higgsless models with warped extra dimensions naturally fulfil all the necessary ingredients to realize this scenario. While current data is unable to discover or exclude these heavy gluons with masses $\approx 850\mathrm{GeV}$, they should be observed at the (7 TeV) LHC with a luminosity $\gtrsim 300{\mathrm{pb}}^{-1}$.

We consider how the measurement of top polarization at the Tevatron can be used to characterize and discriminate among different new physics models that have been suggested to explain the anomalous top forward-backward asymmetry reported at the Tevatron. This has the advantage of catching the essence of the parity-violating effect characteristic to the different suggested new physics models. Other observables constructed from these asymmetries are shown to be useful in discriminating between the models, even after taking into account the statistical errors. Finally, we discuss some signals at the 7 TeV LHC.

We consider the exclusive decays $B\to D^{(*)}\ell \overline{\nu }$ and study the effect of non-$V-A$ structures on the observables. We extend the standard model hadronic current by additional right-handed vector as well as left- and right-handed scalar and tensor contributions and calculate the decay rates including the perturbative corrections up to order ${\alpha }_s$. Using the data of the exclusive semileptonic $b\to c$ decays and recent calculations of the form factors at the nonrecoil point, we discuss the constraints to the wrong-helicity admixtures in the hadronic current.

We derive an analytic expression for the $\mathcal{O}(\alpha )$ radiative correction to the ${\overline{\nu }}_e({\nu }_e)$ spectrum in allowed $\beta$ decay. The $m\to 0$ limit is convergent and leads to a very simple result ($m$ is the electron mass). This is in sharp contrast to the correction to the $e^{-}(e^{+})$ spectrum, that diverges as $m\to 0$, an important difference that we explain on theoretical grounds. After discussing some of their general properties, we use the corrections to the ${\overline{\nu }}_e$ and $e^{-}$ spectra to derive the corresponding correction to the conversion from the $e^{-}$ spectrum to the ${\overline{\nu }}_e$ spectrum, a relation that is of considerable interest for reactor studies of neutrino oscillations.

We consider both velocity-dependent and velocity-independent contributions to spin-dependent (SD) and spin-independent (SI) nuclear scattering (including one-loop corrections) of WIMPless dark matter, in the case where the dark matter candidate is a Majorana fermion. We find that spin-independent scattering arises only from the mixing of exotic squarks or from velocity-dependent terms. Nevertheless (and contrary to the case of minimal supersymmetric standard model neutralino WIMPs), we find a class of models which cannot be detected through SI scattering, but can be detected at IceCube/DeepCore through SD scattering. We study the detection prospects for both SI and SD detection strategies for a large range of Majorana fermion WIMPless model parameters.

Recent results from the MINOS accelerator neutrino experiment suggest a possible difference between ${\nu }_{\mu }$ and ${\overline{\nu }}_{\mu }$ disappearance oscillation parameters, which one may ascribe to a new long-distance potential acting on neutrinos. As a specific example, we consider a model with gauged $B-L_e-2L_{\tau }$ number that contains an extremely light new vector boson $m_{Z^{\prime }}<{10}^{-18}\mathrm{eV}$ and extraordinarily weak coupling ${\alpha }^{\prime }\lesssim {10}^{-52}$ (or larger $m_{Z^{\prime }}$ if cosmology bounds on neutrino decay apply). In that case, differences between ${\nu }_{\mu }\to {\nu }_{\tau }$ and ${\overline{\nu }}_{\mu }\to {\overline{\nu }}_{\tau }$ oscillations can result from a long-range potential due to neutrons in the Earth and the Sun that distinguishes ${\nu }_{\mu }$ and ${\nu }_{\tau }$ on Earth, with a potential difference of $\sim 6\times {10}^{-14}\mathrm{eV}$, and changes sign for antineutrinos. We show that existing solar, reactor, accelerator, and atmospheric neutrino oscillation constraints can be largely accommodated for values of parameters that help explain the possible MINOS anomaly by this new physics, although there is some tension with atmospheric constraints. A long-range interaction, consistent with current bounds, could have very pronounced effects on atmospheric neutrino disappearance in the 15–40 GeV range that will be studied with the IceCube DeepCore array, currently in operation, and can have a significant effect on future high-precision long-baseline oscillation experiments that aim for $\pm 1\%$ sensitivity, in ${\nu }_{\mu }$ and ${\overline{\nu }}_{\mu }$ disappearance, separately. Together, these experiments can extend the reach for new long-distance effects well beyond current bounds and test their relevance to the aforementioned MINOS anomaly. We also point out that long-range potentials originating from the Sun could lead to annual modulations of neutrino data at the percent level, due to the variation of the Earth-Sun distance. A similar phenomenology is shown to apply to other potential new gauge symmetries such as $L-3L_{\tau }$ and $B-3L_{\tau }$.

We investigate the implications for supersymmetry from an assumed absence of any signal in the first period of LHC data taking at 7 TeV center-of-mass energy and with 1 to $7{\mathrm{fb}}^{-1}$ of integrated luminosity. We consider the zero-lepton plus four jets and missing transverse energy signature, and perform a combined fit of low-energy measurements, the dark matter relic density constraint and potential LHC exclusions within a minimal supergravity model. A nonobservation of supersymmetry in the first period of LHC data taking would still allow for an acceptable description of low-energy data and the dark matter relic density in terms of minimal supergravity models, but would exclude squarks and gluinos with masses below 1 TeV.

We revisit here a previous argument due to Wald showing the impossibility of turning an extremal Kerr-Newman black hole into a naked singularity by plunging test particles across the black hole event horizon. We extend Wald’s analysis to the case of near-extremal black holes and show that it is indeed possible to destroy their event horizon, giving rise to naked singularities, by pushing test particles toward the black hole as, in fact, it has been demonstrated explicitly by several recent works. Our analysis allows us to go a step further and to determine the optimal values, in the sense of keeping to a minimum the backreaction effects, of the test particle electrical charge and angular momentum necessary to destroy a given near-extremal Kerr-Newman black hole. We describe briefly a possible realistic scenario for the creation of a Kerr naked singularity from some recently discovered candidates to be rapidly rotating black holes in radio galaxies.

We consider the finite temperature Casimir effect between two concentric spheres due to the vacuum fluctuations of the electromagnetic field in the ($D+1$)-dimensional Minkowski spacetime. Different combinations of perfectly conducting and infinitely permeable boundary conditions are imposed on the spheres. The asymptotic expansions of the Casimir free energies when the dimensionless parameter $\epsilon$, the ratio of the distance between the spheres to the radius of the smaller sphere, is small are derived in both the high temperature region and the low temperature region. It is shown that the leading terms agree with those obtained using the proximity force approximation, which are of order $T{\epsilon }^{1-D}$ in the high temperature region and of order ${\epsilon }^{-D}$ in the low temperature region. Some universal structures are observed in the next two correction terms. The leading terms of the thermal corrections in the low temperature region are also derived. They are found to be finite when $\epsilon \to 0^{+}$ and are of order $T^{D+1}$.

It is shown that different couples of stress-energy and spin tensors of quantum-relativistic fields, which would be otherwise equivalent, are in fact inequivalent if the second law of thermodynamics is taken into account. The proof of the inequivalence is based on the analysis of a macroscopic system at full thermodynamical equilibrium with a macroscopic total angular momentum and a specific instance is given for the free Dirac field, for which we show that the canonical and Belinfante stress-energy tensors are not equivalent. For this particular case, we show that the difference between the predicted angular momentum densities for a rotating system at full thermodynamical equilibrium is a quantum effect, persisting in the nonrelativistic limit, corresponding to a polarization of particles of the order of $\hslash \omega /KT$ ($\omega$ being the angular velocity) and could in principle be measured experimentally. This result implies that specific stress-energy and spin tensors are physically meaningful even in the absence of gravitational coupling and raises the issue of finding the thermodynamically right (or the right class of) tensors. We argue that the maximization of the thermodynamic potential theoretically allows us to discriminate between two different couples, yet for the present we are unable to provide a theoretical method to single out the best couple of tensors in a given quantum field theory. The existence of a nonvanishing spin tensor would have major consequences in hydrodynamics, gravity and cosmology.

In Kaluza-Klein models with an arbitrary number of toroidal internal spaces, we investigate soliton solutions which describe the gravitational field of a massive compact object. Each $d_i$-dimensional torus has its own scale factor $C_i$, $i=1,\dots ,N$, which is characterized by a parameter ${\gamma }_i$. We single out the physically interesting solution corresponding to a pointlike mass. For the general solution we obtain equations of state in the external and internal spaces. These equations demonstrate that the pointlike mass soliton has dustlike equations of state in all spaces. We also obtain the parametrized post-Newtonian parameters, which give the possibility to obtain the formulas for perihelion shift, deflection of light and time-delay of radar echoes. Additionally, the gravitational experiments lead to a strong restriction on the parameters of the model: $\tau =\sum _{i=1}^N{d}_i{\gamma }_i=-(2.1\pm 2.3)\times {10}^{-5}$. The pointlike mass solution with ${\gamma }_1=\dots ={\gamma }_N=(1+\sum _{i=1}^N{d}_i{)}^{-1}$ contradicts this restriction. The condition $\tau =0$ satisfies the experimental limitation and defines a new class of solutions which are indistinguishable from general relativity. We call such solutions latent solitons. Black strings and black branes with ${\gamma }_i=0$ belong to this class. Moreover, the condition of stability of the internal spaces singles out black strings/branes from the latent solitons and leads uniquely to the black string/brane equations of state $p_i=-\epsilon /2$, $i=1,\dots ,N$, in the internal spaces and to the number of the external dimensions $d_0=3$. The investigation of multidimensional static spherically symmetric perfect fluid with a dustlike equation of state in the external space confirms the above results.

It has been proposed that a hidden conformal field theory (CFT) governs the dynamics of low frequency scattering in a general Kerr black hole background. We further investigate this correspondence by mapping higher order corrections to the massless wave equations in a Kerr background to an expansion within the CFT in terms of higher dimension operators. This implies the presence of infinite towers of CFT primary operators with positive conformal dimensions compatible with unitarity. The exact Kerr background softly breaks the conformal symmetry and the scaling dimensions of these operators run with frequency. The scale-invariant fixed point is dual to a degenerate case of flat spacetime.

We derive semianalytic formulas for the local bispectrum and trispectrum from general two-field inflation and provide a simple geometric recipe for building observationally allowed models with large non-Gaussianity. We use the $\delta N$ formalism to express the bispectrum in terms of spectral observables and the transfer functions, which encode the superhorizon evolution of modes. Similarly, we calculate the trispectrum and show that the trispectrum parameter ${\tau }_{\mathrm{NL}}$ can be expressed entirely in terms of spectral observables, which provides a new consistency relation for two-field inflation. To generate observably large non-Gaussianity during inflation, we show that the sourcing of curvature modes by isocurvature modes must be extremely sensitive to a change in the initial conditions orthogonal to the inflaton trajectory and that the amount of sourcing must be nonzero. Under some minimal assumptions, we argue that the first condition is satisfied only when neighboring trajectories in the two-dimensional field space diverge during inflation. Geometrically, this means that the inflaton must roll along a ridge in the potential $V$ for some time during inflation and that its trajectory must turn somewhat in field space. Therefore, it follows that under our assumptions, two-field scenarios with attractor solutions necessarily produce small non-Gaussianity. This explains why it has been so difficult to achieve large non-Gaussianity in two-field inflation and why it has only been achieved in a small fraction of models where the potential and/or the initial conditions are fine-tuned. Some of our conclusions generalize at least qualitatively to multifield inflation and to scenarios where the interplay between curvature and isocurvature modes can be represented by the transfer function formalism.