It was shown recently that mirror fermions, naturally present in a number of directions for new physics, seem to require an inert scalar doublet in order to pass the electroweak precision tests. This provides a further motivation for considering the inert doublet as a dark matter candidate. Moreover, the presence of extra families enhances the standard model Higgs-nucleon coupling, which has crucial impact on the Higgs and dark matter searches. We study the limits on the inert dark matter mass in view of recent Xenon100 data. We find that the mass of the inert dark matter must lie in a very narrow window $75\pm 1\mathrm{GeV}$ while the Higgs boson must weigh more than 400 GeV. For the sake of completeness we discuss the cases with fewer extra families, where the possibility of a light Higgs boson opens up, enlarging the dark matter mass window to $\frac{1}{2}{m}_h\mathrm{\text{−}}76\mathrm{GeV}$. We find that Xenon100 constrains the DM-Higgs interaction, which in turn implies a lower bound on the monochromatic gamma ray flux from DM annihilation in the galactic halo. For the mirror case, the predicted annihilation cross section lies a factor of 4–5 below the current limit set by Fermi LAT, thus providing a promising indirect detection signal.

This paper gathers a selection of standard model predictions issued from the metrology of the Cabibbo-Kobayashi-Maskawa parameters performed by the CKMfitter group. The selection includes purely leptonic decays of neutral and charged $B$, $D$, and $K$ mesons. In the light of the expected measurements from the LHCb experiment, special attention is given to the radiative decay modes of $B$ mesons as well as to the $B$-meson mixing observables, in particular the semileptonic charge asymmetries $a_{\mathrm{SL}}^{d,s}$ which have been recently investigated by the D0 experiment at Tevatron. Constraints arising from rare kaon decays are addressed, in light of both current results and expected performances of future rare kaon experiments. All results have been obtained with the CKMfitter analysis package, featuring the frequentist statistical approach and using Rfit to handle theoretical uncertainties.

Two relativistic approaches are considered to evaluate the quasielastic double-differential and integrated neutrino-nucleus cross sections. One, based on the relativistic impulse approximation, relies on the microscopic description of nuclear dynamics using relativistic mean field theory, and incorporates a description of the final-state interactions. The second is based on the superscaling behavior exhibited by electron scattering data and its applicability, due to the universal character of the scaling function, to the analysis of neutrino scattering reactions. The role played by the vector meson-exchange currents in the two-particle two-hole sector is also incorporated and the results obtained are compared with the recent data for neutrinos measured by the MiniBooNE Collaboration.

We prove the consistency of the Gödel metric with the Horava-Lifshitz gravity whose action involves terms with $z=1$, $z=2$, and $z=3$. We show that, for different relations between the parameters of the theory, this consistency is achieved for different classes of matter; in particular, for the small cosmological constant, it is achieved only for the exotic matter—that is, ghosts or phantom matter.

This work deals with the presence of defect structures in models described by a real scalar field in a diversity of scenarios. The defect structures that we consider are static solutions of the equations of motion that depend on a single spatial dimension. We search for different models, which support the same defect solution, with the very same energy density. We work in flat spacetime, where we introduce and investigate a new class of models. We also work in curved spacetime, within the braneworld context, with a single extra dimension of infinite extent, and there we show how the brane is formed from the static field configuration.

We show that flavor evolution of a system of neutrinos with continuous energy spectra as in supernovae can be understood in terms of the response of individual neutrino flavor-isospins (NFIS’s) to the mean field. In the case of a system initially consisting of ${\nu }_e$ and ${\overline{\nu }}_e$ with the same energy spectrum but different number densities, the mean field is very well approximated by the total angular momentum of a neutrino gyroscope. Assuming that NFIS evolution is independent of the initial neutrino emission angle, the so-called single-angle approximation, we find that the evolution is governed by two types of resonances driven by precession and nutation of the gyroscope, respectively. The net flavor transformation crucially depends on the adiabaticity of evolution through these resonances. We show that the results for the system of two initial neutrino species can be extended to a system of four species with the initial number densities of ${\nu }_e$ and ${\overline{\nu }}_e$ significantly larger than those of ${\nu }_x$ and ${\overline{\nu }}_x$. Further, we find that when the dependence on the initial neutrino emission angle is taken into account in the multiangle approximation, nutation of the mean field is quickly damped out and can be neglected. In contrast, precession-driven resonances still govern the evolution of NFIS’s with different energy and emission angles just as in the single-angle approximation. Our pedagogical and analytic study of collective neutrino oscillations in supernovae provides some insights into these seemingly complicated yet fascinating phenomena.

The $CPT$-even Abelian gauge sector of the standard model extension is represented by the Maxwell term supplemented by $(K_F{)}_{\mu \nu \rho \sigma }{F}^{\mu \nu }{F}^{\rho \sigma }$, where the Lorentz-violating background tensor, $(K_F{)}_{\mu \nu \rho \sigma }$, possesses the symmetries of the Riemann tensor. In the present work, we examine the planar version of this theory, obtained by means of a typical dimensional reduction procedure to ($1+2$) dimensions. The resulting planar electrodynamics is composed of a gauge sector containing six Lorentz-violating coefficients, a scalar field endowed with a noncanonical kinetic term, and a coupling term that links the scalar and gauge sectors. The dispersion relation is exactly determined, revealing that the six parameters related to the pure electromagnetic sector do not yield birefringence at any order. In this model, the birefringence may appear only as a second order effect associated with the coupling tensor linking the gauge and scalar sectors. The equations of motion are written and solved in the stationary regime. The Lorentz-violating parameters do not alter the asymptotic behavior of the fields but induce an angular dependence not observed in the Maxwell planar theory.

Inspiral of compact stellar remnants into massive black holes (MBHs) is accompanied by the emission of gravitational waves at frequencies that are potentially detectable by space-based interferometers. Event rates computed from statistical (Fokker-Planck, Monte-Carlo) approaches span a wide range due to uncertaintities about the rate coefficients. Here we present results from direct integration of the post-Newtonian $N$-body equations of motion describing dense clusters of compact stars around Schwarzschild MBHs. These simulations embody an essentially exact (at the post-Newtonian level) treatment of the interplay between stellar dynamical relaxation, relativistic precession, and gravitational-wave energy loss. The rate of capture of stars by the MBH is found to be greatly reduced by relativistic precession, which limits the ability of torques from the stellar potential to change orbital angular momenta. Penetration of this “Schwarzschild barrier” does occasionally occur, resulting in capture of stars onto orbits that gradually inspiral due to gravitational wave emission; we discuss two mechanisms for barrier penetration and find evidence for both in the simulations. We derive an approximate formula for the capture rate, which predicts that captures would be strongly disfavored from orbits with semi-major axes below a certain value; this prediction, as well as the predicted rate, are verified in the $N$-body integrations. We discuss the implications of our results for the detection of extreme-mass-ratio inspirals from galactic nuclei with a range of physical properties.

A possible source of black hole entropy could be the entanglement of quantum fields inside and outside the horizon. The entanglement entropy of the ground state obeys the area law. However, a correction term proportional to a fractional power of area results when the field is in a superposition of ground and excited states. Inspired by the power-law corrections to entropy and adopting the viewpoint that gravity emerges as an entropic force, we derive modified Newton’s law of gravitation as well as the corrections to Friedmann equations. In a different approach, we obtained power-law-corrected Friedmann equation by starting from the first law of thermodynamics at the apparent horizon of a Friedmann-Robertson-Walker universe, and assuming that the associated entropy with apparent horizon has a power-law-corrected relation. Our study shows a consistency between the obtained results of these two approaches. We also examine the time evolution of the total entropy including the power-law-corrected entropy associated with the apparent horizon together with the matter field entropy inside the apparent horizon and show that the generalized second law of thermodynamics is fulfilled in a region enclosed by the apparent horizon.

While the fundamental object in Riemannian geometry is a metric, closed string theories call for us to put a two-form gauge field and a scalar dilaton on an equal footing with the metric. Here we propose a novel differential geometry that treats the three objects in a unified manner, manifests not only diffeomorphism and one-form gauge symmetry but also $\mathbf{O}(D,D)$ T-duality, and enables us to rewrite the known low energy effective action of them as a single term. Further, we develop a corresponding vielbein formalism and gauge the internal symmetry that is given by a direct product of two local Lorentz groups, $\mathbf{S}\mathbf{O}(1,D-1)\times \overline{\mathbf{S}\mathbf{O}}(1,D-1)$. We comment that the notion of cosmological constant naturally changes.

It was recently realized [Y. F. Cai, T. t. Qiu, R. Brandenberger, and X. m. Zhang, Phys. Rev. D 80, 023511 (2009).] that a model constructed from a Lee-Wick type scalar field theory yields, at the level of homogeneous and isotropic background cosmology, a bouncing cosmology. However, bouncing cosmologies induced by pressureless matter are in general unstable to the addition of relativistic matter (i.e. radiation). Here we study the possibility of obtaining a bouncing cosmology if we add radiation coupled to the Lee-Wick scalar field. This coupling in principle would allow the energy to flow from radiation to matter, thus providing a drain for the radiation energy. However, we find that it takes an extremely unlikely fine-tuning of the initial phases of the field configurations for a sufficient amount of radiative energy to flow into matter. For general initial conditions, the evolution leads to a singularity rather than a smooth bounce.

Theories for new particle and early-Universe physics abound with pseudo-Nambu-Goldstone fields that arise when global symmetries are spontaneously broken. The coupling of these fields to the Chern-Simons term of electromagnetism may give rise to cosmological birefringence (CB), a frequency-independent rotation of the linear polarization of photons as they propagate over cosmological distances. Inhomogeneities in the CB-inducing field may yield a rotation angle that varies across the sky. Here we note that such a spatially-varying birefringence may be correlated with the cosmic microwave background (CMB) temperature. We describe quintessence scenarios where this cross-correlation exists and other scenarios where the scalar field is simply a massless spectator field, in which case the cross-correlation does not exist. We discuss how the cross-correlation between CB-rotation angle and CMB temperature may be measured with CMB polarization. This measurement may improve the sensitivity to the CB signal, and it can help discriminate between different models of CB.

We covariantize the decoupling limit of massive gravity proposed in [de Rham, G. Gabadadze, and A. J. Tolley, Phys. Rev. Lett. 106, 231101 (2011).] and study the cosmology of this theory as a proxy, which embodies key features of the fully nonlinear covariant theory. We first confirm that it exhibits a self-accelerating solution, similar to what has been found in [C. de Rham, G. Gabadadze, L. Heisenberg, and D. Pirtskhalava, Phys. Rev. D 83, 103516 (2011).], where the Hubble parameter corresponds to the graviton mass. For a certain range of parameters fluctuations relative to the self-accelerating background are stable and form an attractor solution. We also show that a degravitating solution can not be constructed in this covariantized proxy theory in a meaningful way. As for cosmic structure formation, we find that the helicity-0 mode of the graviton causes an enhancement relative to $\Lambda \mathrm{CDM}$. For consistency we also compare proxy theories obtained starting from different frames in the decoupling limit and discuss the possibility of obtaining a nonrepresentative proxy theory by choosing the wrong starting frame.

In the simplest (nonquiver) unified theories, fermion families are often treated sequentially and a flavor symmetry may act similarly. As an alternative with nonsequential flavor symmetry, we consider a model based on the group $(T^{\prime }\times Z_2{)}_{\mathrm{global}}\times [SU(3{)}^4{]}_{\mathrm{local}}$ which combines the predictions of $T^{\prime }$ flavor symmetry with the features of a unified quiver gauge theory. The model accommodates the relationships between mixing angles separately for neutrinos, and for quarks, which have been previously predicted with $T^{\prime }$. This quiver unification theory makes predictions of several additional gauge bosons and bifundamental fermions at the TeV scale.

We consider the prospects for liquid scintillation experiments (with a focus on Kamioka Liquid Scintillator Antineutrino Detector [KamLAND]) to detect the flux of electron neutrinos arising from dark matter annihilation in the core of the Sun. We show that, with data already taken, KamLAND can provide the greatest sensitivity to the dark-matter–proton spin-dependent scattering cross section for dark matter lighter than 20 GeV. It is also possible to probe the dark-matter–nucleon spin-independent scattering cross section for isospin-violating dark matter lighter than 10 GeV. KamLAND can thus potentially confirm the dark matter interpretation of the DAMA (DArk MAtter) and CoGeNT signals, utilizing data already taken.

We discuss same-sign dilepton resonances in the simplified model approach. The relevant $\mathrm{SU}(3{)}_Q^J$ quantum numbers are ${\mathbf{1}}_2^{0,1,2}$. For simplicity, we only consider a spin 0 scalar, which is typically referred to as a doubly charged Higgs in the literature. We consider the three simplest cases where the doubly charged Higgs resides in a singlet, doublet or triplet $\mathrm{SU}(2{)}_L$ representation. We discuss production and decay of such a doubly charged Higgs, summarize the current direct search limits, and obtain mass limits in the cases of singlet and doublet for the first time. We also present a complete set of updated indirect search limits. We study the discovery potential at the Large Hadron Collider (LHC) with center of mass energies 7 and 14 TeV for the dominant Drell-Yan pair production with $H^{\pm \pm }$ decay in the $ee$ and $\mu \mu$ channels. We find that at 7 TeV, the LHC with $10{\mathrm{fb}}^{-1}$ luminosity can probe mass of the doubly charged Higgs up to 380 GeV assuming 100% decay to leptons. At 14 TeV, the LHC with $100{\mathrm{fb}}^{-1}$ luminosity can reach a mass of up to 800 GeV.

The present study focuses on the semileptonic $B_c\to D_s^{*}{l}^{+}{l}^{-}$ ($l=\mu$, $\tau$) decay in the standard model (SM) and in the universal extra dimension (UED) model. In addition to the contribution from the flavor changing neutral current (FCNC) transitions the weak annihilation (WA) contribution is also important for this decay. It is found that the WA gives 6.7 times larger branching ratio than the penguin contribution for the decay $B_c\to D_s^{*}{\mu }^{+}{\mu }^{-}$. The contribution from the WA and FCNC transitions are parametrized in terms of the form factors. In this work we first relate the form factors through Ward identities and then express them in terms of $g_{+}(0)$ which is extracted from the decay $B_c\to D_{s^{*}}\gamma$ through the QCD sum rules approach. These form factors are then used to analyze the physical observables such as branching ratio and helicity fractions of the final state $D_s^{*}$ meson in the SM. This analysis is then extended to the UED model where the dependency of the above mentioned physical observables to the compactification radius $R$, the only unknown parameter in the UED model, is studied. It is shown that the helicity fractions of $D_s^{*}$ are sensitive to the UED model especially when we have muons as the final state lepton. This sensitivity is marked up at the low $q^2$ region, irrespective of the choice of the form factors. It is hoped that in the next couple of years the LHC will provide enough data on the $B_c\to D_s^{*}{l}^{+}{l}^{-}$ channel; therefore, these helicity fractions serve as a useful tool to establish new physics predicted by the UED model.

The production of $W$ bosons in association with jets is an important background to new physics at the LHC. Events in which the $W$ carries large transverse momentum and decays leptonically lead to large missing energy and are of particular importance. We show that the left-handed nature of the $W$ coupling, combined with valence quark domination at a $pp$ machine, leads to a large left-handed polarization for both $W^{+}$ and $W^{-}$ bosons at large transverse momenta. The polarization fractions are very stable with respect to QCD corrections. The leptonic decay of the $W^{\pm }$ bosons translates the common left-handed polarization into a strong asymmetry in transverse momentum distributions between positrons and electrons and between neutrinos and antineutrinos (missing transverse energy). Such asymmetries may provide an effective experimental handle on separating $W+\mathrm{\text{jets}}$ from top-quark production, which exhibits very little asymmetry due to C invariance, and from various types of new physics.

We present a physically motivated parametrization of the chiral-even generalized parton distributions in the nonsinglet sector obtained from a global analysis using a set of available experimental data. Our analysis is valid in the kinematical region of intermediate Bjorken $x$ and for $Q^2$ in the multi-GeV region which is accessible at present and currently planned facilities. Relevant data included in our fit are from the nucleon elastic form factor measurements and from deep inelastic scattering experiments. Additional information provided by lattice calculations of the higher moments of generalized parton distributions is also considered. Recently extracted observables from deeply virtual Compton scattering on the nucleon are reproduced by our fit.

The masses of higher $D(nL)$ and $D_s(nL)$ excitations are shown to decrease due to the string contribution, originating from the rotation of the QCD string itself: it lowers the masses by 45 MeV for $L=2$ ($n=1$) and by 65 MeV for $L=3$ ($n=1$). An additional decrease $\sim 100\mathrm{MeV}$ takes place if the current mass of the light (strange) quark is used in a relativistic model. For $D_s(1{}^{3}D_3)$ and $D_s(2P_1^{\mathrm{H}})$ the calculated masses agree with the experimental values for $D_s(2860)$ and $D_s(3040)$, and the masses of $D(2{}^{1}S_0)$, $D(2{}^{3}S_1)$, $D(1{}^{3}D_3)$, and $D(1D_2)$ are in agreement with the new BABAR data. For the yet undiscovered resonances we predict the masses $M(D(2{}^{3}P_2))=2965\mathrm{MeV}$, $M(D(2{}^{3}P_0))=2880\mathrm{MeV}$, $M(D(1{}^{3}F_4))=3030\mathrm{MeV}$, and $M(D_s(1{}^{3}F_2))=3090\mathrm{MeV}$. We show that for $L=2$, 3 the states with $j_q=l+1/2$ and $j_q=l-1/2$ ($J=l$) are almost completely unmixed ($\varphi \simeq -1°$), which implies that the mixing angles $\theta$ between the states with $S=1$ and $S=0$ ($J=L$) are $\theta \approx 40°$ for $L=2$ and $\approx 42°$ for $L=3$.