Modified gravity, known as $f(R)$ gravity, has presently been applied to cosmology as a realistic alternative to dark energy. For this kind of gravity the expansion of the Universe may accelerate while containing only baryons and dark matter. The aim of the present investigation is to place cosmographic constraints on the class of theories of the form $f(R)=R-\alpha /R^n$ within the Palatini approach. Although extensively discussed in recent literature, cosmological tests are inconclusive about the true signal of $n$. This is particularly important to define which kind of corrections (infrared or high-energy) to general relativity this class of theory represents. We shed some light on this question by examining the evolution of the deceleration parameter for these theories. We find that for a large range of $\alpha$, these models can only have positive values for $n$, placing thus a broad restriction on this class of gravity.

We analyze the most salient cosmological features of axions in extensions of the standard model with a gauged anomalous extra $U(1)$ symmetry. The model is built by imposing the constraint of gauge invariance in the anomalous effective action, which is extended with Wess-Zumino counterterms. These generate axionlike interactions of the axions to the gauge fields and a gauged shift symmetry. The scalar sector is assumed to acquire a nonperturbative potential after inflation, at the electroweak phase transition, which induces a mixing of the Stückelberg field of the model with the scalars of the electroweak sector, and at the QCD phase transition. We discuss the possible mechanisms of sequential misalignments which could affect the axions of these models, and generated, in this case, at both transitions. We compute the contribution of these particles to dark matter, quantifying their relic densities as a function of the Stückelberg mass. We also show that models with a single anomalous $U(1)$ in general do not account for the dark energy, due to the presence of mixed $U(1)-SU(3)$ anomalies.

The well-known analogy between a special limit of general relativity and electromagnetism is explored in the context of the Lorentz-violating standard-model extension. An analogy is developed for the minimal standard-model extension that connects a limit of the $CPT$-even component of the electromagnetic sector to the gravitational sector. We show that components of the post-Newtonian metric can be directly obtained from solutions to the electromagnetic sector. The method is illustrated with specific examples including static and rotating sources. Some unconventional effects that arise for Lorentz-violating electrostatics and magnetostatics have an analog in Lorentz-violating post-Newtonian gravity. In particular, we show that even for static sources, gravitomagnetic fields arise in the presence of Lorentz violation.

We present a new phenomenological gravitational waveform model for the inspiral and coalescence of nonprecessing spinning black hole binaries. Our approach is based on a frequency-domain matching of post-Newtonian inspiral waveforms with numerical relativity based binary black hole coalescence waveforms. We quantify the various possible sources of systematic errors that arise in matching post-Newtonian and numerical relativity waveforms, and we use a matching criteria based on minimizing these errors; we find that the dominant source of errors are those in the post-Newtonian waveforms near the merger. An analytical formula for the dominant mode of the gravitational radiation of nonprecessing black hole binaries is presented that captures the phenomenology of the hybrid waveforms. Its implementation in the current searches for gravitational waves should allow cross-checks of other inspiral-merger-ringdown waveform families and improve the reach of gravitational-wave searches.

We analyze Aharonov-Bohm radiation of charged fermions from oscillating solenoids and cosmic strings. We find that the angular pattern of the radiation has features that differ significantly from that for bosons. For example, fermionic radiation in the lowest harmonic is approximately isotropically distributed around an oscillating solenoid, whereas for bosons the radiation is dipolar. We also investigate the spin polarization of the emitted fermion-antifermion pair. Fermionic radiation from kinks and cusps on cosmic strings is shown to depend linearly on the ultraviolet cutoff, suggesting strong emission at an energy scale comparable to the string energy scale.

One of the strongest arguments against the cosmological constant as an explanation of the current epoch of accelerated cosmic expansion is the existence of an earlier, dynamical acceleration, i.e. inflation. We examine the likelihood that acceleration is an occasional phenomenon, putting stringent limits on the length of any accelerating epoch due to minimally coupled dark energy between recombination and the recent acceleration; such an epoch must last less than 0.05 e-fold (at $z>2$) or the matter power spectrum is modified by more than 20%.

The KATRIN neutrino experiment is a next-generation tritium beta decay experiment aimed at measuring the mass of the electron neutrino to better than 200 meV at 90% C.L. Because of its intense tritium source, KATRIN can also serve as a possible target for the process of neutrino capture, ${\nu }_e+{}^3\mathrm{H}\to {}^3\mathrm{He}^{+}+e^{-}$. The latter process, possessing no energy threshold, is sensitive to the cosmic neutrino background ($\mathrm{C}\nu \mathrm{B}$). In this paper, we explore the potential sensitivity of the KATRIN experiment to the relic neutrino density. The KATRIN experiment is sensitive to a $\mathrm{C}\nu \mathrm{B}$ overdensity ratio of $2.0\times {10}^9$ over standard concordance model predictions (at 90% C.L.), addressing the validity of certain speculative cosmological models.

Directional detection is a promising search strategy to discover Galactic dark matter. Taking advantage on the rotation of the Solar System around the Galactic center through the dark matter halo, it allows us to show a direction dependence of weakly interacting massive particle (WIMP) events. Even though the goal of directional search is to identify a WIMP positive detection, exclusion limits are still needed for very low exposure with a rather large background contamination, such as the one obtained with prototype experiments. Data of directional detectors are composed of energy and a 3D track for all recoiling nuclei. However, to set robust exclusion limits, we focus on the angular part of the event distribution, arguing that the energy part of the background distribution is unknown. As the angular distributions of both background and WIMP events are known, a Bayesian approach to set exclusion limits is possible. In this paper, a new statistical method based on an extended likelihood is proposed, compared to existing ones, and is shown to be optimal. Eventually, a comprehensive study of the effect of a detector configuration on exclusion limits is presented. It includes the effect of having or not sense recognition, a finite angular resolution, taking into account energy threshold as well as some astrophysical uncertainties.

A class of nonsupersymmetric extensions of the standard model is proposed in which there is a multiplicity of light scalar doublets in a multiplet of a nonabelian family group with the standard model Higgs doublet. Anthropic tuning makes the latter light, and consequently the other scalar doublets remain light because of the family symmetry. The family symmetry greatly constrains the pattern of flavor-changing neutral-current interactions (FCNC) and $p$ decay operators coming from scalar-exchange. Such models show that useful constraints on model-building can come from an extended naturalness principle when the electroweak scale is anthropically tuned.

We investigate the form factors of the chiral-odd nucleon matrix element of the tensor current. In particular, we aim at the anomalous tensor magnetic form factors of the nucleon within the framework of the SU(3) and SU(2) chiral quark-soliton model. We consider $1/N_c$ rotational corrections and linear effects of SU(3) symmetry breaking with the symmetry-conserving quantization employed. We first obtain the results of the anomalous tensor magnetic moments for the up and down quarks: ${\kappa }_T^u=3.56$ and ${\kappa }_T^d=1.83$, respectively. The strange anomalous tensor magnetic moment is yielded to be ${\kappa }_T^s=0.2\sim -0.2$, that is compatible with zero. We also calculate the corresponding form factors ${\kappa }_T^q(Q^2)$ up to a momentum transfer $Q^2\le 1{\mathrm{GeV}}^2$ at a renormalization scale of $0.36{\mathrm{GeV}}^2$.

In a previous work regarding the interaction of two $\rho (770)$ resonances, the $f_2(1270)$ ($J^{PC}=2^{++}$) resonance was obtained dynamically as a two-$\rho$ molecule with a very strong binding energy, 135 MeV per $\rho$ particle. In the present work we use the $\rho \rho$ interaction in spin 2 and isospin 0 channel to show that the resonances ${\rho }_3(1690)$ ($3^{--}$), $f_4(2050)$ ($4^{++}$), ${\rho }_5(2350)$ ($5^{--}$), and $f_6(2510)$ ($6^{++}$) are basically molecules of increasing number of $\rho (770)$ particles. We use the fixed center approximation of the Faddeev equations to write the multibody interaction in terms of the two-body scattering amplitudes. We find the masses of the states very close to the experimental values and we get an increasing value of the binding energy per $\rho$ as the number of $\rho$ mesons is increased.

Prospects for discovery of the standard model Higgs boson are examined at center-of-mass energies of 7 and 10 TeV at the CERN Large Hadron Collider. We perform a simulation of the signal and principal backgrounds for Higgs boson production and decay in the $W^{+}{W}^{-}$ dilepton mode, finding good agreement with the ATLAS and CMS collaboration estimates of signal significance at 14 TeV for Higgs boson masses near $m_H=160\mathrm{GeV}$. At the lower energy of 7 TeV, using the same analysis cuts as these collaborations, we compute expected signal sensitivities of about 2 standard deviations ($\sigma$’s) at $m_H=160\mathrm{GeV}$ in the ATLAS case, and about $3.6\sigma$ in the CMS case for $1{\mathrm{fb}}^{-1}$ of integrated luminosity. Integrated luminosities of $8{\mathrm{fb}}^{-1}$ and $3{\mathrm{fb}}^{-1}$ are needed in the ATLAS case at 7 and 10 TeV, respectively, for $5\sigma$ level discovery. In the CMS case, the numbers are $2{\mathrm{fb}}^{-1}$ and $1{\mathrm{fb}}^{-1}$ at 7 and 10 TeV. Our different stated expectations for the two experiments arise from the more restrictive analysis cuts in the CMS case and from the different event samples in the two cases. Recast as exclusion limits, our results show that with $1{\mathrm{fb}}^{-1}$ of integrated luminosity at 7 TeV, the LHC may be able to exclude $m_H$ values in the range 160 to 180 GeV provided no signal is seen.

In this paper, we suggest that there are two different individual two-dimensional conformal field theories (CFTs) holographically dual to the Kerr-Newman black hole, coming from the corresponding two possible limits—the Kerr/CFT and Reissner-Nordström/CFT correspondences, namely, there exist the Kerr-Newman/CFTs dualities. A probe scalar field at low frequencies turns out can exhibit two different two-dimensional conformal symmetries (named by $J$ and $Q$ pictures, respectively) in its equation of motion when the associated parameters are suitably specified. These twofold dualities are supported by the matchings of entropies, absorption cross sections, and real-time correlators computed from both the gravity and the CFT sides. Our results lead to a fascinating “microscopic hair conjecture”—for each macroscopic hair parameter, in addition to the mass of a black hole in the Einstein-Maxwell theory, there should exist an associated holographic ${\mathrm{CFT}}_2$ description.

It is shown that the hidden conformal symmetry, namely $SO(2,2)\sim SL(2,R{)}_L\times SL(2,R{)}_R$ symmetry, of the nonextremal dyonic Reissner-Nordström black hole can be probed by a charged massless scalar field at low frequencies. The existence of such hidden conformal symmetry suggests that the field theory holographically dual to the four-dimensional Reissner-Nordström black hole indeed should be a two-dimensional conformal field theory (CFT). Although the associated ${\mathrm{AdS}}_3$ structure does not explicitly appear in the near horizon geometry, the primary parameters of the dual ${\mathrm{CFT}}_2$ can be exactly obtained without the necessity of embedding the four-dimensional Reissner-Nordström black hole into five-dimensional spacetime. The duality is further supported by comparing the absorption cross sections and real-time correlators obtained from both the CFT and the gravity sides.

The vacuum expectation value of fermionic current is evaluated for a massive spinor field in spacetimes with an arbitrary number of toroidally compactified spatial dimensions in the presence of a constant gauge field. By using the Abel-Plana type summation formula and the zeta-function technique we present the fermionic current in two different forms. Nontrivial topology of the background spacetime leads to the Aharonov-Bohm effect for the fermionic current induced by the gauge field. The current is a periodic function of the magnetic flux with the period equal to the flux quantum. In the absence of gauge field it vanishes for special cases of untwisted and twisted fields. Applications of general formulas to Kaluza-Klein type models and to cylindrical and toroidal carbon nanotubes are given. In the absence of magnetic flux the total fermionic current in carbon nanotubes vanishes, due to the cancellation of contributions from two different sublattices of the hexagonal lattice of graphene.

We present the first quantitative comparison of two independent general-relativistic hydrodynamics codes, the whisky code and the sacra code. We compare the output of simulations starting from the same initial data and carried out with the configuration (numerical methods, grid setup, resolution, gauges) which for each code has been found to give consistent and sufficiently accurate results, in particular, in terms of cleanness of gravitational waveforms. We focus on the quantities that should be conserved during the evolution (rest mass, total mass energy, and total angular momentum) and on the gravitational-wave amplitude and frequency. We find that the results produced by the two codes agree at a reasonable level, with variations in the different quantities but always at better than about 10%.

We show that the inclusion of simple anisotropic pressures stops the isotropic Friedmann universe being a stable attractor as an initial or final singularity is approached when pressures can exceed the energy density. This shows that the situation with isotropic pressures, studied earlier in the context of cyclic and ekpyrotic cosmologies, is not generic, and Kasner-like behavior occurs when simple pressure anisotropies are present. We find all the asymptotic behaviors and determine the dynamics when the anisotropic principal pressures are proportional to the density. We expect distortions and anisotropies to be significantly amplified through a simple cosmological bounce in cyclic or ekpyrotic cosmologies when ultrastiff pressures are present.

A soft-wall warped extra dimension allows one to relax the tight constraints imposed by electroweak data in conventional Randall-Sundrum models. We investigate a setup, where the lepton flavor structure of the standard model is realized by split fermion locations. Bulk fermions with general locations are not analytically tractable in a soft-wall background, so we follow a numerical approach to perform the Kaluza-Klein reduction. Lepton flavor violation is induced by the exchange of Kaluza-Klein gauge bosons. We find that rates for processes such as muon-electron conversion are significantly reduced compared to hard-wall models, allowing for a Kaluza-Klein scale as low as 2 TeV. Accommodating small neutrino masses forces one to introduce a large hierarchy of scales into the model, making pressing the question of a suitable stabilization mechanism.

We study the phase diagram of two-flavor dense QCD at finite isospin and baryon chemical potentials in the framework of the Nambu–Jona-Lasinio model. We focus on the case with arbitrary isospin chemical potential ${\mu }_{\mathrm{I}}$ and small baryon chemical potential ${\mu }_{\mathrm{B}}\le {\mu }_{\mathrm{B}}^{\chi }$ where ${\mu }_{\mathrm{B}}^{\chi }$ is the critical chemical potential for the first-order chiral phase transition to happen at ${\mu }_{\mathrm{I}}=0$. The ${\mu }_{\mathrm{I}}-{\mu }_{\mathrm{B}}$ phase diagram shows a rich phase structure since the system undergoes a crossover from a Bose-Einstein condensate of charged pions to a BCS superfluid with condensed quark-antiquark Cooper pairs when ${\mu }_{\mathrm{I}}$ increases at ${\mu }_{\mathrm{B}}=0$, and a nonzero baryon chemical potential serves as a mismatch between the pairing species. We observe a gapless pion condensation phase near the quadruple point $({\mu }_{\mathrm{I}},{\mu }_{\mathrm{B}})=(m_{\pi },M_{\mathrm{N}}-1.5m_{\pi })$ where $m_{\pi }$, $M_{\mathrm{N}}$ are the vacuum masses of pions and nucleons, respectively. The first-order chiral phase transition becomes a smooth crossover when ${\mu }_{\mathrm{I}}>0.82m_{\pi }$. At very large isospin chemical potential, ${\mu }_{\mathrm{I}}>6.36m_{\pi }$, an inhomogeneous Larkin-Ovchinnikov-Fulde-Ferrell superfluid phase, appears in a window of ${\mu }_{\mathrm{B}}$, which should in principle exist for arbitrary large ${\mu }_{\mathrm{I}}$. Between the gapless and the Larkin-Ovchinnikov-Fulde-Ferrell phases, the pion superfluid phase and the normal quark matter phase are connected by a first-order phase transition. In the normal phase above the superfluid domain, we find that charged pions are still bound states even though ${\mu }_{\mathrm{I}}$ becomes very large, which is quite different from that at finite temperature. Our phase diagram is in good agreement with that found in imbalanced cold atom systems.

We study the anomalous magnetic moment of the muon in supersymmetric $E_6$ models and generic $\mathrm{U}(1{)}^{\prime }$ models to probe the model reactions and to find constraints on the large parameter space of these models. For future searches, by imposing the existing bounds coming from collider searches and theoretical considerations upon the $\mathrm{U}(1{)}^{\prime }$ model parameters, we examine the lightest Higgs boson mass $m_h$ and the mass of the additional $Z$ boson $m_{Z_2}$ in such singlet extensions of the MSSM. We observed that not only supersymmetric $E_6$ models but also generic $\mathrm{U}(1{)}^{\prime }$ models are sensitive to the imposition of the considered bounds. Indeed, without the muon anomaly constraints $E_6$ models and generic $\mathrm{U}(1{)}^{\prime }$ models can predict $m_h$ as large as $\sim 150\mathrm{GeV}$ and $\sim 180\mathrm{GeV}$, respectively. However, in addition to the mentioned constraints when a $1\sigma$ range for the anomalous magnetic moment of the muon is considered, we observe that generic $\mathrm{U}(1{)}^{\prime }$ models do not favor the mass of the lightest Higgs boson to be larger than 140 GeV; it should be smaller than 135 GeV in $E_6$ models.