We discuss some cosmological consequences of a general model of coupled quintessence in which the phenomenological coupling between the cold dark matter and dark energy is a function of the cosmic scale factor $ϵ(a)$. This class of models presents cosmological solutions in which the Universe is currently dominated by an exotic component, but will eventually be dominated by cold dark matter in the future. This dynamical behavior is considerably different from the standard $\Lambda \mathrm{CDM}$ evolution, and may alleviate some conflicts in reconciling the idea of the dark energy-dominated universe with observables in String/M theory. Finally, we investigate some observational features of this model and discuss some constraints on its parameters from current Type Ia supernovae (SNe Ia), baryonic acoustic oscillations (BAO) and cosmic microwave background (CMB) data.

Cosmography is a useful tool to constrain cosmological models, in particular, dark energy models. In the case of modified theories of gravity, where the equations of motion are generally quite complicated, cosmography can contribute to select realistic models without imposing arbitrary choices a priori. Indeed, its reliability is based on the assumptions that the universe is homogeneous and isotropic on large scale and luminosity distance can be “tracked” by the derivative series of the scale factor $a(t)$. We apply this approach to induced gravity brane-world models where an $f(R)$ term is present in the brane effective action. The virtue of the model is to self-accelerate the normal and healthy Dvali-Gabadadze-Porrati branch once the $f(R)$ term deviates from the Hilbert-Einstein action. We show that the model, coming from a fundamental theory, is consistent with the $\Lambda \mathrm{CDM}$ scenario at low redshift. We finally estimate the cosmographic parameters fitting the Union2 Type Ia Supernovae data set and the distance priors from baryon acoustic oscillations and then provide constraints on the present day values of $f(R)$ and its second and third derivatives.

The gravitational-wave instability of $r$ modes in rapidly rotating compact stars is believed to spin them down to angular frequencies $\Omega \sim 0.1{\Omega }_{\mathrm{Kepler}}$ soon after their birth in a supernova. We point out that the $r$-mode perturbation also impacts the neutrino cooling and viscosity in hot compact stars via processes that restore weak equilibrium. We illustrate this fact with a simple model of spin-down due to gravitational-wave emission in compact stars composed entirely of three-flavor degenerate quark matter (a strange quark star). Nonequilibrium neutrino cooling of this oscillating fluid matter is quantified. Our results imply that a consistent treatment of the thermal and spin-frequency evolution of a young and hot compact star is a requisite in estimating the persistence of gravitational waves from such a source.

A search for extremely high energy cosmic neutrinos has been carried out with the IceCube Neutrino Observatory. The main signals in the search are neutrino-induced energetic charged leptons and their rate depends on the neutrino-nucleon cross section. The upper limit on the neutrino flux has implications for possible new physics beyond the standard model such as the extra space-time dimension scenarios which lead to a cross section much higher than the standard particle physics prediction. In this study we constrain the neutrino-nucleon cross section at energies beyond ${10}^9\mathrm{GeV}$ with the IceCube observation. The constraints are obtained as a function of the extraterrestrial neutrino flux in the relevant energy range, which accounts for the astrophysical uncertainty of neutrino production models.

One of the goals of the current LIGO-GEO-Virgo science run is to identify transient gravitational wave (GW) signals in near real time to allow follow-up electromagnetic (EM) observations. An EM counterpart could increase the confidence of the GW detection and provide insight into the nature of the source. Current GW-EM campaigns target potential host galaxies based on overlap with the GW sky error box. We propose a new statistic to identify the most likely host galaxy, ranking galaxies based on their position, distance, and luminosity. We test our statistic with Monte Carlo simulations of GWs produced by coalescing binaries of neutron stars and black holes, one of the most promising sources for ground-based GW detectors. Considering signals accessible to current detectors, we find that when imaging a single galaxy, our statistic correctly identifies the true host $\sim 20\%$ to $\sim 50\%$ of the time, depending on the masses of the binary components. With five narrow-field images the probability of imaging the true host increases from $\sim 50\%$ to $\sim 80\%$. When collectively imaging groups of galaxies using large field-of-view telescopes, the probability improves from $\sim 30\%$ to $\sim 60\%$ for a single image and from $\sim 70\%$ to $\sim 90\%$ for five images. For the advanced generation of detectors (circa $2015+$), and considering binaries within 100 Mpc (the reach of the galaxy catalogue used), the probability is $\sim 40\%$ for one narrow-field image, $\sim 75\%$ for five narrow-field images, $\sim 65\%$ for one wide-field image, and $\sim 95\%$ for five wide-field images, irrespective of binary type.

In this paper we suggest the generalization of $k_T$ factorization formula for inclusive gluon production for the dense-dense parton system scattering. It turns out that the soft gluon production with transverse momentum $p_T$ is suppressed by an additional Sudakov-like factor that depends on the $p_T^2/Q_s^2$ ratio in good agreement with the first numerical calculation in the color glass condensate approach by J. P. Blaizot, T. Lappi, and Y. Mehtar-Tan.

Taking into account the constraints on the free parameters of the littlest Higgs model with $T$ parity (called the LHT model) from some rare decay processes, such as $\mu \to e\gamma$ and $\mu \to 3e$, we consider the contributions of the LHT model to the lepton flavor violating (LFV) processes $e^{+}{e}^{-}\to l_i{\overline{l}}_j$ and $\gamma \gamma \to l_i{\overline{l}}_j$ ($i\ne j$). We find that the LHT model can indeed produce significant contributions to these LFV processes and its LFV signal might have a chance of being observed in the future International Linear Collider experiments.

We have searched for flavor-changing neutral current decays and lepton-number-violating decays of $D^{+}$ and $D_s^{+}$ mesons to final states of the form $h^{\pm }{e}^{\mp }{e}^{+}$, where $h$ is either $\pi$ or $K$. We use the complete samples of CLEO-c open-charm data, corresponding to integrated luminosities of $818{\mathrm{pb}}^{-1}$ at the center-of-mass energy $E_{\mathrm{CM}}=3.774\mathrm{GeV}$ containing $2.4\times {10}^6$ $D^{+}{D}^{-}$ pairs and $602{\mathrm{pb}}^{-1}$ at $E_{\mathrm{CM}}=4.170\mathrm{GeV}$ containing $0.6\times {10}^6$ $D_s^{*\pm }{D}_s^{\mp }$ pairs. No signal is observed in any channel, and we obtain 90% confidence level upper limits on branching fractions $\mathcal{B}(D^{+}\to {\pi }^{+}{e}^{+}{e}^{-})<5.9\times {10}^{-6}$, $\mathcal{B}(D^{+}\to {\pi }^{-}{e}^{+}{e}^{+})<1.1\times {10}^{-6}$, $\mathcal{B}(D^{+}\to K^{+}{e}^{+}{e}^{-})<3.0\times {10}^{-6}$, $\mathcal{B}(D^{+}\to K^{-}{e}^{+}{e}^{+})<3.5\times {10}^{-6}$, $\mathcal{B}(D_s^{+}\to {\pi }^{+}{e}^{+}{e}^{-})<2.2\times {10}^{-5}$, $\mathcal{B}(D_s^{+}\to {\pi }^{-}{e}^{+}{e}^{+})<1.8\times {10}^{-5}$, $\mathcal{B}(D_s^{+}\to K^{+}{e}^{+}{e}^{-})<5.2\times {10}^{-5}$, and $\mathcal{B}(D_s^{+}\to K^{-}{e}^{+}{e}^{+})<1.7\times {10}^{-5}$.

Interactions between the inflaton and any additional fields can lead to isolated bursts of particle production during inflation (for example from parametric resonance or a phase transition). Inflationary particle production leaves localized features in the spectrum and bispectrum of the observable cosmological fluctuations, via the Infra-Red (IR) cascading mechanism. We focus on a simple prototype interaction $g^2(\varphi -{\varphi }_0{)}^2{\chi }^2$ between the inflaton, $\varphi$, and isoinflaton, $\chi$; extending previous work on this model in two directions. First, we quantify the magnitude of the produced non-Gaussianity by extracting the moments of the probability distribution function from lattice field theory simulations. We argue that the bispectrum feature from particle production might be observable for reasonable values of the coupling, $g^2$. Second, we develop a detailed analytical theory of particle production and IR cascading during inflation, which is in excellent agreement with numerical simulations. Our formalism improves significantly on previous approaches by consistently incorporating both the expansion of the universe and also metric perturbations. We use this new formalism to estimate the shape of the bispectrum from particle production, showing this to be distinguishable from other mechanisms that predict large non-Gaussianity.

We show that the Aharonov-Bohm effect in the nuclear matrix model [K. Hashimoto, N. Iizuka, andP. Yi , J. High Energy Phys. 10 (2010), 3.] derives the statistical nature of nucleons in holographic QCD. For $N_c=\mathrm{\text{odd}}$ (even), the nucleon is shown to be a fermion (boson).

In this paper we begin the study of renormalizations in the heterotically deformed $\mathcal{N}=(0,2)$ $CP(N-1)$ sigma models. In addition to the coupling constant $g^2$ of the undeformed $\mathcal{N}=(2,2)$ model, there is the second coupling constant $\gamma$ describing the strength of the heterotic deformation. We calculate both $\beta$ functions, ${\beta }_g$ and ${\beta }_{\gamma }$ at one loop, determining the flow of $g^2$ and $\gamma$. Under a certain choice of the initial conditions, the theory is asymptotically free. The $\beta$ function for the ratio $\rho ={\gamma }^2/g^2$ exhibits an infrared fixed point at $\rho =1/2$. Formally this fixed point lies outside the validity of the one-loop approximation. We argue, however, that the fixed point at $\rho =1/2$ may survive to all orders. The reason is the enhancement of symmetry—emergence of a chiral fermion flavor symmetry in the heterotically deformed Lagrangian—at $\rho =1/2$. Next we argue that ${\beta }_{\rho }$ formally obtained at one loop, is exact to all orders in the large-$N$ (planar) approximation. Thus, the fixed point at $\rho =1/2$ is definitely the feature of the model in the large-$N$ limit.

Using a generalized self-similar secondary infall model, which accounts for tidal torques acting on the halo, we analyze the velocity profiles of halos in order to gain intuition for N-body simulation results. We analytically calculate the asymptotic behavior of the internal radial and tangential kinetic energy profiles in different radial regimes. We then numerically compute the velocity anisotropy and pseudo–phase-space density profiles and compare them to recent N-body simulations. For cosmological initial conditions, we find both numerically and analytically that the anisotropy profile asymptotes at small radii to a constant set by model parameters. It rises on intermediate scales as the velocity dispersion becomes more radially dominated and then drops off at radii larger than the virial radius where the radial velocity dispersion vanishes in our model. The pseudo–phase-space density is universal on intermediate and large scales. However, its asymptotic slope on small scales depends on the halo mass and on how mass shells are torqued after turnaround. The results largely confirm N-body simulations but show some differences that are likely due to our assumption of a one-dimensional phase space manifold.

$N$-body simulations have revealed a wealth of information about dark matter halos; however, their results are largely empirical. Using analytic means, we attempt to shed light on simulation results by generalizing the self-similar secondary infall model to include tidal torque. In this first of two papers, we describe our halo formation model and compare our results to empirical mass profiles inspired by $N$-body simulations. Each halo is determined by four parameters. One parameter sets the mass scale and the other three define how particles within a mass shell are torqued throughout evolution. We choose torque parameters motivated by tidal torque theory and $N$-body simulations and analytically calculate the structure of the halo in different radial regimes. We find that angular momentum plays an important role in determining the density profile at small radii. For cosmological initial conditions, the density profile on small scales is set by the time rate of change of the angular momentum of particles as well as the halo mass. On intermediate scales, however, $\rho \propto r^{-2}$, while $\rho \propto r^{-3}$ close to the virial radius.

In higher dimensions than four, conventional uniqueness theorem in asymptotically flat space-times does not hold, i.e., black objects cannot be classified only by the mass, angular momentum, and charge. In this paper, we define multipole moments for black objects and show that Myers-Perry black hole and black ring can be distinguished by quadrupole moments. This consideration gives us a new insight for the uniqueness theorem for black objects in higher dimensions.

Scalar field models of inflation based on a large nonminimal coupling to gravity $\xi$, in particular, Higgs inflation, may violate unitarity at an energy scale $\Lambda \sim M_p/\xi \ll M_p$. In this case the model is incomplete at energy scales relevant to inflation. Here we propose a new unitarity-conserving model of Higgs inflation. The completion of the theory is achieved via additional interactions which are proportional to products of the derivatives of the Higgs doublet. The resulting model differs from the original version of Higgs inflation in its prediction for the spectral index, with a classical value $n=0.974$. In the case of a nonsupersymmetric model, quantum corrections are likely to strongly modify the tree-level potential, suggesting that supersymmetry or a gauge singlet scalar inflaton is necessary for a completely successful model.

Semiclassical states for the Wheeler-DeWitt equation of a Bianchi type I model in the presence of a scalar field are analyzed. It is outlined how this scheme can effectively describe more general situations, where the curvature of the Bianchi type IX model and a proper potential term for the scalar field are present. The introduction of a cosmological constant term accounts for the quasi-isotropization mechanism which bridges the proposed framework with a late isotropic phase. This result makes the semiclassical Bianchi I model a plausible scenario for the Universe preinflationary phase.

Deviations from general relativity in order to explain cosmic acceleration generically have both time and scale-dependent signatures in cosmological data. We extend our previous work by investigating model-independent gravitational deviations in bins of redshift and length scale, by incorporating further cosmological probes such as temperature-galaxy and galaxy-galaxy cross-correlations, and by examining correlations between deviations. Markov Chain Monte Carlo likelihood analysis of the model-independent parameters fitting current data indicates that at low redshift general relativity deviates from the best fit at the 99% confidence level. We trace this to two different properties of the CFHTLS weak lensing data set and demonstrate that COSMOS weak lensing data does not show such deviation. Upcoming galaxy survey data will greatly improve the ability to test time and scale-dependent extensions to gravity and we calculate the constraints that the BigBOSS galaxy redshift survey could enable.

It is an empirical question whether photons always obey Bose-Einstein statistics, but devising and interpreting experimental tests of photon statistics can be a challenge. The nonrelativistic cross section for Compton scattering illustrates how a small admixture $\nu$ of wrong-sign statistics leads to a loss of gauge invariance; there is a large anomalous amplitude for scattering timelike photons. Nevertheless, one can interpret the observed transparency of the solar wind plasma at low frequencies as a bound $\nu <{10}^{-25}$ if Lorentz symmetry is required. If there is instead a universal preferred frame, the bound is $\nu <{10}^{-14}$, still strong compared with previous results.

In the framework of the simplest little Higgs model, we perform a comprehensive study for the pair productions of the pseudoscalar boson $\eta$ and standard model-like Higgs boson $h$ at LHC, namely $gg(b\overline{b})\to \eta \eta$, $gg(q\overline{q})\to \eta h$, and $gg(b\overline{b})\to hh$. These production processes provide a way to probe the couplings between Higgs bosons. We find that the cross section of $gg\to \eta \eta$ always dominates over that of $b\overline{b}\to \eta \eta$. When the Higgs boson $h$ which mediates these two processes is on-shell, their cross sections can reach several thousand fb and several hundred fb, respectively. When the intermediate state $h$ is off-shell, those two cross sections are reduced by 2 orders of magnitude, respectively. The cross sections of $gg\to \eta h$ and $q\overline{q}\to \eta h$ are about in the same order of magnitude, which can reach $\mathcal{O}({10}^2\mathrm{fb})$ for a light $\eta$ boson. Besides, compared with the standard model prediction, the cross section of a pair of standard model-like Higgs bosons production at LHC can be enhanced sizably. Finally, we briefly discuss the observable signatures of $\eta \eta$, $\eta h$, and $hh$ at the LHC.

We perform updated and detailed calculations of the complete next-to-leading order set of electroweak radiative corrections to parity-violating $e^{-}{e}^{-}\to e^{-}{e}^{-}(\gamma )$ scattering asymmetries at energies relevant for the ultraprecise Møller experiment to be performed at JLab. Our numerical results are presented for a range of experimental cuts and the relative importance of various contributions is analyzed. We also provide very compact expressions analytically free from nonphysical parameters and show them to be valid for fast, yet accurate estimations.