We study the growth of structures in modified gravity models where the Poisson equation and the relationship between the two Newtonian potentials are modified by explicit functions of space and time. This parametrization applies to the $f(R)$ models and more generally to screened modified gravity models. We investigate the linear and weakly nonlinear regimes using the “standard” perturbative approach and a resummation technique, while we use the spherical dynamics to go beyond low-order results. This allows us to estimate the matter density power spectrum and bispectrum from linear to highly nonlinear scales, the full probability distribution of the density contrast on weakly nonlinear scales, and the halo mass function. We analyze the impact of modifications of gravity on these quantities for a few realistic models. In particular, we find that the standard one-loop perturbative approach is not sufficiently accurate to probe these effects on the power spectrum, and it is necessary to use resummation methods even on weakly nonlinear scales, which provide the best observational window for modified gravity as relative deviations from general relativity do not grow significantly on smaller scales where theoretical predictions become increasingly difficult.

We find new, simple cosmological solutions with flat, open, and closed spatial geometries. The metric and the Stückelberg fields are given explicitly, showing nontrivial configurations of the Stückelberg in the usual Friedmann-Lemaître-Robertson-Walker coordinates. The solutions exhibit self-acceleration, while being free from ghost instabilities. Our solutions can be extended to include inhomogeneous dust collapse represented by the Lemaître-Tolman-Bondi metric as well. Thus, our results can be used not only to describe homogeneous and isotropic cosmology but also to study gravitational collapse in massive gravity.

Lepton masses and mixing angles via localization of 5-dimensional fields in the bulk are revisited in the context of Randall-Sundrum models. The Higgs is assumed to be localized on the IR brane. Three cases for neutrino masses are considered: (a) The higher-dimensional neutrino mass operator (LH.LH), (b) Dirac masses, and (c) Type I seesaw with bulk Majorana mass terms. Neutrino masses and mixing as well as charged lepton masses are fit in the first two cases using ${\chi }^2$ minimization for the bulk mass parameters, while varying the $\mathcal{O}(1)$ Yukawa couplings between 0.1 and 4. Lepton flavor violation is studied for all the three cases. It is shown that large negative bulk mass parameters are required for the right-handed fields to fit the data in the LH.LH case. This case is characterized by a very large Kaluza-Klein (KK) spectrum and relatively weak flavor-violating constraints at leading order. The zero modes for the charged singlets are composite in this case, and their corresponding effective 4-dimensional Yukawa couplings to the KK modes could be large. For the Dirac case, good fits can be obtained for the bulk mass parameters, $c_i$, lying between 0 and 1. However, most of the “best-fit regions” are ruled out from flavor-violating constraints. In the bulk Majorana terms case, we have solved the profile equations numerically. We give example points for inverted hierarchy and normal hierarchy of neutrino masses. Lepton flavor violating rates are large for these points. We then discuss various minimal flavor violation schemes for Dirac and bulk Majorana cases. In the Dirac case with minimal-flavor-violation hypothesis, it is possible to simultaneously fit leptonic masses and mixing angles and alleviate lepton flavor violating constraints for KK modes with masses of around 3 TeV. Similar examples are also provided in the Majorana case.

We critically examine interpretations of hypothetical supersymmetric LHC signals, fitting to alternative wrong models of supersymmetry breaking. The signals we consider are some of the most constraining on the sparticle spectrum: invariant mass distributions with edges and endpoints from the golden decay chain $\tilde{q}\to q{\chi }_2^0(\to {\tilde{l}}^{\pm }{l}^{\mp }q)\to {\chi }_1^0{l}^{+}{l}^{-}q$. We assume a constrained minimal supersymmetric standard model (CMSSM) point to be the ‘correct’ one, but fit the signals instead with minimal gauge mediated supersymmetry breaking models (mGMSB) with a neutralino quasistable lightest supersymmetric particle, minimal anomaly mediation and large volume string compactification models. Minimal anomaly mediation and large volume scenario can be unambiguously discriminated against the CMSSM for the assumed signal and $1{\mathrm{fb}}^{-1}$ of LHC data at $\sqrt{s}=14\mathrm{TeV}$. However, mGMSB would not be discriminated on the basis of the kinematic endpoints alone. The best-fit point spectra of mGMSB and CMSSM look remarkably similar, making experimental discrimination at the LHC based on the edges or Higgs properties difficult. However, using rate information for the golden chain should provide the additional separation required.

The minimal 3-3-1 model is perturbative until energies around 4–5 TeV, posing a challenge to generate neutrino masses at eV scale, mainly if one aims to take advantage of the seesaw mechanism. As a means to circumvent this problem, we propose a modification of the model such that it accommodates the type I and type II seesaw mechanisms altogether. We show that the conjunction of both mechanisms yield a neutrino mass expression suppressed by a high power of the cutoff scale, $M^5$, in its denominator. With such a suppression term, we naturally obtain neutrino masses at eV scale when $M$ is around few TeV. We also investigate the size of lepton flavor violation through the process $\mu \to e\gamma$.

We study the phenomenology of a supersymmetric scenario where the next-to-lightest superparticle is the lighter stau and is long-lived due to a very weakly coupled lightest superparticle, such as the gravitino. We investigate the LHC sensitivity and its dependence on the superparticle spectrum with an emphasis on strong production and decay. We do not assume any high-scale model for supersymmetry breaking but work along the lines of simplified models. Devising cuts that yield a large detection efficiency in the whole parameter space, we determine the LHC’s discovery and exclusion potential. This allows us to derive robust limits on $m_{{\tilde{\tau }}_1}$, $m_{\tilde{g}}$, a common $m_{\tilde{q}}$, and $m_{{\tilde{t}}_1}$. We briefly discuss the prospects for observing stopped staus.

We consider a supersymmetric version of the standard model extended by an additional $U(1{)}_{B-L}$. This model can be embedded in an mSUGRA-inspired model where the mass parameters of the scalars and gauginos unify at the scale of grand unification. In this class of models the renormalization group equation evolution of gauge couplings as well as of the soft SUSY-breaking parameters require the proper treatment of gauge kinetic mixing. We first show that this has a profound impact on the phenomenolgy of the $Z^{\prime }$ and as a consequence the current LHC bounds on its mass are reduced significantly from about 1970 GeV to 1790 GeV. They are even further reduced if the $Z^{\prime }$ can decay into supersymmetric particles. Secondly, we show that in this way sleptons can be produced at the LHC in the 14 TeV phase with masses of several hundred GeV. In the case of squark and gluino masses in the multi-TeV range, this might become an important discovery channel for sleptons up to 800 GeV (900 GeV) for an integrated luminosity of $100{\mathrm{fb}}^{-1}$ ($300{\mathrm{fb}}^{-1}$).

We analyze the prompt ${\rm Y}(nS)$ production cross sections measured by the CMS and LHCb collaborations at the LHC. A reasonable agreement between the data and $k_t$-factorization predictions is found in all cases.

Jet vetoes play an important role at the LHC in the search for the Higgs and ultimately in precise measurements of its properties. Many Higgs analyses divide the cross section into exclusive jet bins to maximize the sensitivity in different production and decay channels. For a given jet category, the veto on additional jets introduces sensitivity to soft and collinear emissions, which causes logarithms in the perturbative expansion that need to be resummed to obtain precise predictions. We study the higher-order resummation properties of several conceptually distinct kinematic variables that can be used to veto jets in hadronic collisions. We consider two inclusive variables, the scalar sum over $p_T$ and beam thrust, and two corresponding exclusive variables based on jet algorithms, namely, the largest $p_T$ and largest beam thrust of a jet. The inclusive variables can, in principle, be resummed to higher orders. We show that for the jet-based variables, there are dual effects due to clustering in the jet algorithm for both large and small jet radius $R$ that make a complete resummation at or beyond next-to-leading logarithmic order challenging. For $R\sim 1$, the clustering of soft and collinear emissions gives $\mathcal{O}(1)$ contributions starting at next-to-next-to-leading logarithm that are not reproduced by an all-orders soft-collinear factorization formula and therefore are not automatically resummed by it. For $R\ll 1$, clustering induces logarithms of $R$ that contribute at next-to-leading logarithm in the exponent of the cross section, which cannot be resummed with currently available methods. We explicitly compute the leading jet clustering effects at $\mathcal{O}({\alpha }_s^2)$ and comment on their numerical size.

The Double Chooz experiment has observed 8249 candidate electron antineutrino events in 227.93 live days with 33.71 GW-ton-years ($\mathrm{\text{reactor power}}\times \mathrm{\text{detector mass}}\times \mathrm{\text{live time}}$) exposure using a $10.3{\mathrm{m}}^3$ fiducial volume detector located at 1050 m from the reactor cores of the Chooz nuclear power plant in France. The expectation in case of ${\theta }_{13}=0$ is 8937 events. The deficit is interpreted as evidence of electron antineutrino disappearance. From a rate plus spectral shape analysis we find ${sin}^{2}2{\theta }_{13}=0.109\pm 0.030(\mathrm{stat})\pm 0.025(\mathrm{syst})$. The data exclude the no-oscillation hypothesis at 99.8% CL ($2.9\sigma$).

The static part of the heavy quark potential has been shown to be closely related to the spectrum of the rectangular Wilson loop. In particular the lowest lying positive frequency peak encodes the late time evolution of the two-body system, characterized by a complex potential. While initial studies assumed a perfect separation of early- and late-time physics, where a simple Lorentzian (Breit-Wigner) shape suffices to describe the spectral peak, we argue that scale decoupling in general is not complete. Thus early-time, i.e., nonpotential effects significantly modify the shape of the lowest peak. We derive on general grounds an improved peak distribution that reflects this fact. Application of the improved fit to nonperturbative lattice QCD spectra now yields a potential that is compatible with a transition to a deconfined screening plasma.

According to the standard prescriptions, zero-temperature string theories can be extended to finite temperature by compactifying their time directions on a so-called “thermal circle” and implementing certain orbifold twists. However, the existence of a topologically nontrivial thermal circle leaves open the possibility that a gauge flux can pierce this circle—i.e., that a nontrivial Wilson line (or equivalently a nonzero chemical potential) might be involved in the finite-temperature extension. In this paper, we concentrate on the zero-temperature heterotic and Type I strings in ten dimensions, and survey the possible Wilson lines which might be introduced in their finite-temperature extensions. We find a rich structure of possible thermal string theories, some of which even have nontraditional Hagedorn temperatures, and we demonstrate that these new thermal string theories can be interpreted as extrema of a continuous thermal free-energy “landscape.” Our analysis also uncovers a unique finite-temperature extension of the heterotic $SO(32)$ and $E_8\times E_8$ strings which involves a nontrivial Wilson line, but which—like the traditional finite-temperature extension without Wilson lines—is metastable in this thermal landscape.

It is known that the symmetric (massless) state of the Nambu-Jona-Lasinio model in $2+1$ dimensions in a magnetic field $B$ is not the ground state of the system at zero temperature due to the presence of a negative linear in $|\sigma +i\pi |$ term in the effective potential for the composite fields $\sigma \sim \overline{\psi }\psi$ and $\pi \sim \overline{\psi }i{\gamma }^5\psi$, while the quadratic term is always positive (a tachyon is absent). We find that finite temperature is a necessary ingredient for the tachyonic instability of the symmetric state to occur. Utilizing the Schwinger-Keldysh real-time formalism, we calculate the dispersion relations for the fluctuation modes of the composite fields $\sigma$ and $\pi$. We demonstrate the presence of the tachyonic instability of the symmetric state for the coupling constant that exceeds a certain critical value which vanishes as temperature tends to zero in accordance with the phenomenon of magnetic catalysis.

In our previous paper [N. Fukui, K.-I. Kondo, A. Shibata, and T. Shinohara, Phys. Rev. D 82, 045015 (2010)], we have shown that the Jackiw-Nohl-Rebbi (JNR) two-instanton generates a circular loop of magnetic monopole in the four-dimensional Euclidean SU(2) Yang-Mills theory. On the other hand, it is claimed in Brower et al. [Phys. Rev. D 55, 6313 (1997); Nucl. Phys. B, Proc. Suppl. 53, 488 (1997)] that the ’t Hooft two-instanton does not generate magnetic monopole loop. It seems that the two results are inconsistent with each other, since the JNR two-instanton converges to the ’t Hooft two-instanton in a certain limit. In this paper, we clarify that the two results are compatible with each other by demonstrating how the magnetic monopole loop generated from the JNR two-instanton deforms in the process of taking the ’t Hooft two-instanton limit.

We explore the cosmological dynamics of an effective $f(R)$ model constructed from a renormalization group improvement of the Einstein-Hilbert action, using the nonperturbative beta functions of the exact renormalization group equation. The resulting $f(R)$ model has some remarkable properties. It naturally exhibits an unstable de Sitter era in the ultraviolet (UV), dynamically connected to a stable de Sitter era in the IR, via a period of radiation and matter domination, thereby describing a nonsingular universe. We find that the UV de Sitter point is one of an infinite set, which makes the UV renormalization group fixed point inaccessible to classical cosmological evolution. In the vicinity of the fixed point, the model behaves as $R^2$ gravity, while it correctly recovers general relativity at solar system scales. In this simplified model, the fluctuations are too large to be the observed ones, and more ingredients in the action are needed.

We present the continuation of J. Majár [Phys. Rev. D 80, 104028 (2009)] to solve the instantaneous spin precession equations for the spin-orbit, spin-spin, and quadrupole-monopole contributions. In this paper we present the solution of the quadrupole-monopole contributions to the precession equations. For eccentric orbits we use the true anomaly parametrization, and for circular orbits our results are given explicitly in terms of the time variable. We also give a detailed analysis of the different effects of the spin interactions, and investigate which of these are relevant in the present case. We work in the framework of the post-Newtonian expansion.

We experiment with several new modifications to the Baumgarte-Shapiro-Shibata-Nakamura formulation of Einstein’s field equation, and demonstrate how these modifications affect the stability of numerical black hole evolution. With these modifications, we obtain accurate and stable simulations of both single excised Kerr-Schild black holes and punctured binary black holes.

We discuss methods based on principal component analysis to constrain the dark energy equation of state using a combination of Type Ia supernovae at low redshift and spectroscopic measurements of varying fundamental couplings at higher redshifts. We discuss the performance of this method when future better-quality data sets are available, focusing on two forthcoming European southern observatory (ESO) spectrographs—Echelle spectrograph for rocky exoplanet and stable spectroscopic observations (ESPRESSO) for the very large telescope (VLT) and Cosmic dynamics explorer (CODEX) for the European extremely large telescope (E-ELT)—which include these measurements as a key part of their science cases. These can realize the prospect of a detailed characterization of dark energy properties almost all the way up to redshift 4.

Kaiser redshift-space distortion formula describes well the clustering of galaxies in redshift surveys on small scales, but there are numerous additional terms that arise on large scales. Some of these terms can be described using Newtonian dynamics and have been discussed in the literature, while the others require proper general relativistic description that was only recently developed. Accounting for these terms in galaxy clustering is the first step toward tests of general relativity on horizon scales. The effects can be classified as two terms that represent the velocity and the gravitational potential contributions. Their amplitude is determined by effects such as the volume and luminosity distance fluctuation effects and the time evolution of galaxy number density and Hubble parameter. We compare the Newtonian approximation often used in the redshift-space distortion literature to the fully general relativistic equation, and show that Newtonian approximation accounts for most of the terms contributing to velocity effect. We perform a Fisher matrix analysis of detectability of these terms and show that in a single tracer survey they are completely undetectable. To detect these terms one must resort to the recently developed methods to reduce sampling variance and shot noise. We show that in an all-sky galaxy redshift survey at low redshift the velocity term can be measured at a few sigma if one can utilize halos of mass $M\ge {10}^{12}{h}^{-1}{M}_{\odot }$ (this can increase to $10\mathrm{\text{−}}\sigma$ or more in some more optimistic scenarios), while the gravitational potential term itself can only be marginally detected. We also demonstrate that the general relativistic effect is not degenerate with the primordial non-Gaussian signature in galaxy bias, and the ability to detect primordial non-Gaussianity is little compromised.

We explore the paradigm in which inflation is driven by a four-dimensional strongly coupled dynamic with a nonminimal coupling to gravity. We introduce a model where the inflaton is identified with the glueball field of a pure Yang-Mills theory. We introduce the dilatonic-like glueball action, which is obtained by requiring saturation of the underlying Yang-Mills trace anomaly at the effective action level. We couple the resulting action nonminimally to gravity. We demonstrate that it is possible to achieve successful inflation with the confining scale of the underlying Yang-Mills theory naturally of the order of the grand unified energy scale. We also argue that the metric formulation gives a more consistent picture for models of composite inflation than the Palatini one. Finally, we show that, within the metric formulation, the model nicely respects tree-level unitarity for the scattering of the inflaton field all the way to the Planck scale.