We introduce and study a new class of power-counting nonrenormalizable gauge theories in four space-time dimensions. The Lagrangian is an arbitrary function of the self-dual part of the field strength. The resulting perturbation theory has the property that whenever two derivatives act on an internal line propagator, the result is a delta function and the line collapses to a point. This means that there remains at most one derivative on each internal line, which gives improved ultra-violet behavior. For many purposes, this class of theories behaves just like ordinary Yang-Mills theory. In particular, they all share the Yang-Mills theory MHV amplitudes. Moreover, these theories remain constructible (in the generalized sense), with the higher-point tree-level scattering amplitudes obtainable from the lower-point amplitudes using the BCFW recursion relations, and adding new amplitudes at every particle number. Also, the square of these gauge-theory amplitudes gives the scattering amplitudes of “deformations” of general relativity, at least for the low particle numbers that we checked. We compute the one-loop beta function of the first new coupling constant, and find it to be positive, which signals the associated nonrenormalizable interaction becoming important in the ultraviolet.

We construct a stretched (aka warped) anti–de Sitter black hole in three dimensions supported by a real scalar field configuration. The latter is regular everywhere outside and on the horizon. No-hair theorems in three dimensions demand the matter be coupled to the curvature in a nonminimal way; however, this coupling can still be of the Horndeski type, i.e. yielding second order field equations similar to those appearing in the context of Galileon theories. These warped-anti–de Sitter black holes exhibit interesting thermodynamical properties, such as finite Hawking temperature and entropy. We compute the black hole entropy in the gravity theory and speculate on the possibility of this to admit a microscopic description in terms of a dual (warped) conformal field theory. We also discuss the inner and outer black hole mechanics.

We explore the Minkowski functionals (MFs) of weak lensing convergence map to distinguish between $f(R)$ gravity and the general relativity (GR). The mock weak lensing convergence maps are constructed with a set of high-resolution simulations assuming different gravity models. It is shown that the lensing MFs of $f(R)$ gravity can be considerably different from that of GR because of the environmentally dependent enhancement of structure formation. We also investigate the effect of lensing noise on our results, and find that it is likely to distinguish F5, F6, and GR gravity models with a galaxy survey of $\sim 3000{\text{degree}}^2$ and with a background source number density of $n_g=30{\text{arcmin}}^{-2}$, comparable to an upcoming survey dark energy survey (DES). We also find that the $f(R)$ signal can be partially degenerate with the effect of changing cosmology, but combined use of other observations, such as the cosmic microwave background (CMB) data, can help break this degeneracy.

We explore an effective supergravity action in the presence of a massless gauge field which contains a Gauss-Bonnet term as well as a dilaton field. We construct a new class of black brane solutions of this theory with a Lifshitz asymptotic by fixing the parameters of the model such that the asymptotic Lifshitz behavior can be supported. Then we construct the well-defined finite action through the use of the counterterm method. We also obtain two independent constants along the radial coordinate by combining the equations of motion. Calculations of these two constants at infinity through the use of the large-$r$ behavior of the metric functions show that our solution respects the no-hair theorem. Furthermore, we combine these two constants in order to get a constant $\mathcal{C}$ which is proportional to the energy of the black brane. We calculate this constant at the horizon in terms of the temperature and entropy and at large-$r$ in terms of the geometrical mass. By calculating the value of the energy density through the use of the counterterm method, we obtain the relation between the energy density, the temperature, and the entropy. This relation is the generalization of the well-known Smarr formula for AdS black holes. Finally, we study the thermal stability of our black brane solution and show that it is stable under thermal perturbations.

Inflationary $\alpha$-attractor models in supergravity, which provide excellent fits to the latest observational data, are based on the Poincaré disk hyperbolic geometry. We refine these models by constructing Kähler potentials with built-in inflaton shift symmetry and by making a canonical choice of the Goldstino Kähler potential. The refined models are stable with respect to all scalar fields at all $\alpha$; no additional stabilization terms are required. The scalar potential $V$ has a nearly Minkowski minimum at small values of the inflaton field $\phi$ and an infinitely long de Sitter (dS) valley of constant depth and width at large $\phi$. Because of the infinite length of this shift-symmetric valley, the initial value of the inflaton field at the Planck density is expected to be extremely large. We show that the inflaton field $\phi$ does not change much until all fields lose their energy and fall to the bottom of the dS valley at large $\phi$. This provides natural initial conditions for inflation driven by the inflaton field slowly rolling along the dS valley toward the minimum of the potential at small $\phi$. A detailed description of this process is given for $\alpha$-attractors in supergravity, but we believe that our general conclusions concerning naturalness of initial conditions for inflation are valid for a broad class of inflationary models with sufficiently flat potentials.

The search for weakly interacting massive particles (WIMPs) by direct detection faces an encroaching background due to coherent neutrino-nucleus scattering. As the sensitivity of these experiments improves, the question of how to best distinguish a dark matter signal from neutrinos will become increasingly important. A proposed method of overcoming this so-called “neutrino floor” is to utilize the directional signature that both neutrino- and dark-matter-induced recoils possess. We show that directional experiments can indeed probe WIMP-nucleon cross sections below the neutrino floor with little loss in sensitivity due to the neutrino background. In particular we find at low WIMP masses (around 6 GeV) the discovery limits for directional detectors penetrate below the nondirectional limit by several orders of magnitude. For high WIMP masses (around 100 GeV), the nondirectional limit is overcome by a factor of a few. Furthermore we show that even for directional detectors which can only measure one- or two-dimensional projections of the three-dimensional recoil track, the discovery potential is only reduced by a factor of 3 at most. We also demonstrate that while the experimental limitations of directional detectors, such as sense recognition and finite angular resolution, have a detrimental effect on the discovery limits, it is still possible to overcome the ultimate neutrino background faced by nondirectional detectors.

We present a model of leptoquarks (LQs) with a significant partial branching ratio into an extra sector, taken to be a viable dark matter candidate, other than the canonical lepton and jets final state. For LQs with mass around 500 GeV, the model reproduces the recent excess claimed by the CMS Collaboration in the ${\ell }^{+}{\ell }^{-}jj{\cancel{E}}_{\mathrm{T}}$ final state: the event rate, the distribution in the dilepton invariant mass and the rapidity range are compatible with the data. The model is compatible with other collider bounds including LQ searches, as well as bounds from meson mixing and decays. Prospects of discovery at run II of the LHC are discussed.

We propose an extension of the Standard Model in which baryon number is promoted to be part of a non-Abelian gauge symmetry at high energies. Specifically, we consider the gauge group $SU(4)\times SU(2{)}_L\times U(1{)}_X$, where the $SU(4)$ unifies baryon number and color. This symmetry is spontaneously broken down to the Standard Model gauge group at a scale which can be as low as a few TeV. The $SU(4)$ structure implies that each SM quark comes along with an uncolored quark partner, the lightest of which is stabilized by the generalized baryon number symmetry and can play the role of dark matter. We explore circumstances under which one can realize a model of asymmetric dark matter whose relic abundance is connected to the observed baryon asymmetry, and discuss unique signatures that can be searched for at the LHC.

We show that the recently reported anomalies in $b\to s{\mu }^{+}{\mu }^{-}$ transitions, as well as the long-standing $g_{\mu }-2$ discrepancy, can be addressed simultaneously by a new massive Abelian gauge boson with loop-induced coupling to muons. Such a scenario typically leads to a stable dark matter candidate with a thermal relic density close to the observed value. Dark matter in our model couples dominantly to leptons, hence signals in direct detection experiments lie well below the current sensitivity. The LHC, in combination with indirect detection searches, can test this scenario through distinctive signatures with muon pairs and missing energy.

Neutrino oscillations are well established and the relevant parameters determined with good precision, except for the $CP$ phase, in terms of a unitary lepton mixing matrix. Seesaw extensions of the Standard Model predict unitarity deviations due to the admixture of heavy isosinglet neutrinos. We provide a complete description of the unitarity and universality deviations in the light-neutrino sector. Neutrino oscillation experiments involving electron or muon neutrinos and antineutrinos are fully described in terms of just three new real parameters and a new $CP$ phase, in addition to the ones describing oscillations with unitary mixing. Using this formalism we describe the implications of nonunitarity for neutrino oscillations and summarize the model-independent constraints on heavy-neutrino couplings that arise from current experiments.

We report a two-detector measurement of the propagation speed of neutrinos over a baseline of 734 km. The measurement was made with the NuMI beam at Fermilab between the near and far MINOS detectors. The fractional difference between the neutrino speed and the speed of light is determined to be $(v/c-1)=(1.0\pm 1.1)\times {10}^{-6}$, consistent with relativistic neutrinos.

It has been recently found that for the near extremal Kerr black holes appearing of zero damped modes (accompanied by quasinormal mode branching) signifies about inapplicability of the regime of small perturbations and the onset of turbulence. Here we show that this phenomenon is not limited by Kerr or Kerr-Newman solutions only, but also takes place for rotating dilatonic black holes for which we have found zero damped modes both numerically and analytically. We have also shown that, contrary to recent claims, there is no instability of a charged massive scalar field in the background of the rotating dilatonic black hole under physically adequate boundary conditions. Analytic expression for dominant quasinormal frequencies is deduced in the regime of large coupling $qQ$, where $q$ and $Q$ are the field and black hole charges, respectively.

We show that fuzzy spheres are solutions of Lorentzian Ishibashi-Kawai-Kitazawa-Tsuchiya-type matrix models. The solutions serve as toy models of closed noncommutative cosmologies where big bang/crunch singularities appear only after taking the commutative limit. The commutative limit of these solutions corresponds to a sphere embedded in Minkowski space. This “sphere” has several novel features. The induced metric does not agree with the standard metric on the sphere, and, moreover, it does not have a fixed signature. The curvature computed from the induced metric is not constant, has singularities at fixed latitudes (not corresponding to the poles) and is negative. Perturbations are made about the solutions, and are shown to yield a scalar field theory on the sphere in the commutative limit. The scalar field can become tachyonic for a range of the parameters of the theory.

We cross-correlate cosmic microwave background (CMB) lensing and galaxy weak lensing maps using the Planck 2013 and 2015 data and the $154{\mathrm{deg}}^2$ Canada-France-Hawaii Telescope Lensing Survey (CFHTLenS). This measurement probes large-scale structure at intermediate redshifts $\approx 0.9$, between the high- and low-redshift peaks of the CMB and CFHTLenS lensing kernels, respectively. Using the noise properties of these data sets and standard Planck 2015 $\mathrm{\Lambda }\mathrm{CDM}$ cosmological parameters, we forecast a signal-to-noise ratio $\approx 4.6$ for the cross-correlation. We find that the noise level of our actual measurement agrees well with this estimate, but the amplitude of the signal lies well below the theoretical prediction. The best-fit amplitudes of our measured cross-correlations are $A_{2013}=0.48\pm 0.26$ and $A_{2015}=0.44\pm 0.22$, using the 2013 and 2015 Planck CMB lensing maps, respectively, where $A=1$ corresponds to the fiducial Planck 2015 $\mathrm{\Lambda }\mathrm{CDM}$ prediction. Due to the low measured amplitude, the detection significance is moderate ($\approx 2\sigma$) and the data are in tension with the theoretical prediction $(\approx 2–2.5\sigma )$. The tension is reduced somewhat when compared to predictions using WMAP9 parameters, for which we find $A_{2013}=0.56\pm 0.30$ and $A_{2015}=0.52\pm 0.26$. We consider various systematic effects, finding that photometric redshift uncertainties, contamination by intrinsic alignments, and effects due to the masking of galaxy clusters in the Planck 2015 CMB lensing reconstruction are able to help resolve the tension at a significant level ($\approx 10\%$ each). An overall multiplicative bias in the CFHTLenS shear data could also play a role, which can be tested with existing data. We close with forecasts for measurements of the CMB lensing—galaxy lensing cross-correlation using ongoing and future weak lensing surveys, which will definitively test the significance of the tension in our results with respect to $\mathrm{\Lambda }\mathrm{CDM}$.

We study chromo-natural inflation in the axiverse. More precisely, we investigate natural inflation with two axions coupled with a SU(2) gauge field. Assuming a hierarchy between the coupling constants, we find that for certain initial conditions, conventional natural inflation commences and continues for tens of $e$-foldings, and subsequently chromo-natural inflation takes over from natural inflation. For these solutions, we expect that the predictions are in agreement with observations on CMB scales. Moreover, since chromo-natural inflation occurs in the latter part of the inflationary stage, chiral primordial gravitational waves are produced in the interesting frequency range higher than ${10}^{-11}\mathrm{Hz}$, which might be detectable by future gravitational wave observations.

We explore the dark matter and collider phenomenology of the minimal gauged ${\mathrm{U}(1)}_{\mathrm{B}}$ model, consisting of a leptophobic $Z_{\mathrm{B}}$ gauge boson, and an accompanying Higgs $S_{\mathrm{B}}$. By requirement of anomaly cancellation, the fermion sector naturally contains a dark matter candidate—a Majorana isosinglet $\chi$ stabilized by an inherent $Z_2$ symmetry. The absence of evidence for $Z$ prime dijet resonances at the LHC suggests that the scale of symmetry breaking is ${\mathrm{\Lambda }}_{\mathrm{B}}\gtrsim 500\mathrm{GeV}$. Saturation of dark matter abundance together with limits on the direct detection cross section (dominated by Higgs exchange) constrains the Higgs mixing angle to $|\theta |\lesssim 0.22$. For small mixing angles of $|\theta |\lesssim {10}^{-3}$, the $\mathcal{O}(10\%)$ branching fractions of the fermion loop-mediated $S_{\mathrm{B}}\to \gamma \gamma$, $Z\gamma$, $ZZ$ modes may provide clues about the fermion content of the model at the LHC.

We combine symmetry structures of ordinary (parallel directions) and dual (transversal directions) coordinates to construct the Dirac-Born-Infeld theory. The ordinary coordinates are associated with the Neumann boundary conditions and the dual coordinates are associated with the Dirichlet boundary conditions. Gauge fields become scalar fields by exchanging the ordinary and dual coordinates. A gauge transformation of a generalized metric is governed by the generalized Lie derivative. The gauge transformation of the massless closed string theory gives the $C$-bracket, but the gauge transformation of the open string theory gives the $F$-bracket. The $F$-bracket with the strong constraints is different from the Courant bracket by an exact one-form. This exact one-form should come from the one-form gauge field. Based on a symmetry point of view, we deduce a suitable action with a nonzero $H$-flux at the low-energy level. From an equation of motion of the scalar dilaton, it defines a generalized scalar curvature. Finally, we construct a double sigma model with a boundary term and show that this model with constraints is classically equivalent to the ordinary sigma model.

The Bose-Einstein condensation of bound pairs made of oppositely charged fermions in a magnetic field is investigated. We find that the condensation temperature shows the magnetic catalysis effect in weak coupling and the inverse magnetic catalysis effect in strong coupling. The different responses to the magnetic field can be attributed to the competition between the dimensional reduction by Landau orbitals in pairing dynamics and the anisotropy of the kinetic spectrum of fluctuations (bound pairs in the normal phase).