We make a detailed analysis of the proton decay in a supersymmetric SO(10) model proposed by K. Babu, I. Gogoladze, P. Nath, and R. Syed. We introduce quark mixing, and find that this model can generate fermion mass without breaking the experimental bound on proton decay. We also predict large Cabibbo-Kobayashi-Maskawa (CKM) unitarity violations. The CKM matrix $V$ in this paper is defined as normal, i.e. $d_i^{\prime }=V^{ij}{d}_j$, where $ij$ run from 1 to 3. The primed field is the weak eigenstate and the unprimed field is the mass eigenstate.

Low-energy experiments involving kaon, $B$-meson, $D$-meson, and hyperon flavor-changing neutral transitions have confirmed the loop-induced flavor-changing neutral current picture of the standard model. The continuing study of these processes is essential to further refine this picture and ultimately understand the flavor dynamics. In this paper we consider deviations from the standard model in the charm sector and their effect on flavor-changing neutral current processes. Specifically, we parametrize new physics in terms of left- and right-handed anomalous couplings of the $W$ boson to the charm quark. We present a comprehensive study of existing constraints and point out those measurements that are most sensitive to new physics of this type.

We discuss kinematic methods for determining the masses of the particles in events at a hadron collider in which a pair of identical particles is produced with each decaying via a series of on shell intermediate beyond-the-standard model (BSM) particles to visible standard model (SM) particles and an invisible particle (schematically, $pp\to ZZ+\mathrm{\text{jets}}$ with $Z\to Aa\to Bba\to Ccba\to \dots \to cba\dots +N$ where $a,b,c,\dots$ are visible SM particles or groups of SM particles, $A,B,C,\dots$ are on shell BSM particles, and $N$ is invisible). This topology arises in many models including supersymmetry (SUSY) processes such as squark and gluino pair production and decay. We present the detailed procedure for the case of $Z\to 3\mathrm{\text{visible particles}}+N$ and demonstrate that the masses obtained from the kinematic procedure are independent of the model by comparing SUSY to universal extra dimensions.

We derive constraints on the mass insertion parameters from the recent measurements of $B_s–{\overline{B}}_s$ mixing, and discuss their implications on SUSY breaking mediation mechanisms and SUSY flavor models. Some SUSY flavor models are already excluded or disfavored by $B_s–{\overline{B}}_s$ mixing. We also discuss how to test the SM and SUSY models in the future experiments, by studying other $CP$ violating observables related to $b\to s$ transition, such as the time-dependent $CP$ asymmetry in $B_d\to \varphi K_S$ and the direct $CP$ asymmetry in $B\to X_s\gamma$.

We present a calculation of the leading SU(3)-breaking $\mathcal{O}(p^3)$ corrections to the electromagnetic moments and charge radius of the lowest-lying decuplet resonances in covariant chiral perturbation theory. In particular, the magnetic dipole moment of the members of the decuplet is predicted fixing the only low-energy constant (LEC) present up to this order with the well-measured magnetic dipole moment of the ${\Omega }^{-}$. We predict ${\mu }_{\Delta }^{++}=6.04(13)$ and ${\mu }_{\Delta }^{+}=2.84(2)$, which agree well with the current experimental information. For the electric quadrupole moment and the charge radius, we use state-of-the-art lattice QCD results to determine the corresponding LECs, whereas for the magnetic octupole moment there is no unknown LEC up to the order considered here, and we obtain a pure prediction. We compare our results with those reported in large $N_c$, lattice QCD, heavy-baryon chiral perturbation theory, and other models.

Neutrinos of energies of about 5–20 MeV are produced due to the stellar collapse or merger events that trigger the gamma-ray burst. Also low energy MeV neutrinos are produced within the fireball due to electron-positron annihilation and nucleonic bremsstrahlung. Many of these neutrinos will propagate through the dense and relativistic magnetized plasma of the fireball. We have studied the possibility of resonant oscillation of ${\nu }_e\leftrightarrow {\nu }_{\mu ,\tau }$ by taking into account the neutrino oscillation parameters from SNO, super Kamiokande, and liquid scintillator detector. Using the resonance condition, we have calculated the resonance length for these neutrinos and also for the fireball observables, like lepton asymmetry and the baryon load that are estimated based on the assumed fireball radius of 100 km.

Quantum fluctuations in the QED vacuum generate nonlinear effects, such as peculiar induced electromagnetic fields. In particular, we show here that an electrically neutral particle, possessing a magnetic dipole moment, develops an induced electric dipole-type moment with unusual angular dependence, when immersed in a quasistatic, constant external electric field. The calculation of this effect is done in the framework of the Euler-Heisenberg effective QED Lagrangian, corresponding to the weak field asymptotic expansion of the effective action to one-loop order. It is argued that the neutron might be a good candidate to probe this signal of nonlinearity in QED.

We discuss some details of the model proposed [M. Aoki, S. Kanemura, and O. Seto, Phys. Rev. Lett. 102, 051805 (2009)], in which neutrino oscillation, dark matter, and baryon asymmetry of the Universe would be simultaneously explained by the TeV-scale physics without introducing very high mass scales. An exact discrete $Z_2$ symmetry is introduced, under which new particle contents (a real singlet scalar field, a pair of charged singlet scalar fields, and TeV-scale right-handed neutrinos) are assigned to have odd quantum number, whereas ordinary gauge fields, quarks and leptons, and two Higgs doublets are even. Tiny neutrino masses are generated at the three-loop level due to the exact $Z_2$ symmetry, by which stability of the dark matter candidate is also guaranteed. The extra Higgs doublet is required not only for the tiny neutrino masses but also for successful electroweak baryogenesis. We discuss phenomenological properties of the model, and find that there are successful scenarios in which the above three problems are solved simultaneously under the constraint from current experimental data. We then discuss predictions in such scenarios at ongoing and future experiments. It turns out that the model provides discriminative predictions especially in Higgs physics and dark matter physics, so that it is testable in the near future.

The chiral limit of the $\rho$ and $\sigma$ masses and widths is discussed. We work within the inverse amplitude method to one loop in SU(2) chiral perturbation theory and analyze the consequences that all chiral logarithms cancel out in the $\rho$ channel, while they do not cancel for the $\sigma$ case, and how they strongly influence the properties of this latter resonance. Our results confirm and explain the different behavior of the $\sigma$ and $\rho$ poles for $N_C$ not far from 3, but we extend the analysis to very large $N_C$, where the behavior of these two resonances is reanalyzed. We note that the rather natural requirement of consistency between resonance saturation and unitarization imposes useful constraints. By looking only at the $\rho$ channel, and within the single resonance approximation, we find that the masses of the first vector and scalar meson nonets, invoked in the single resonance approximation, turn out to be degenerated in the large $N_C$ limit. On the contrary we show that, for sufficiently large $N_C$, the scalar meson evolution lies beyond the applicability reach of the one-loop inverse amplitude method and if the scalar channel is also incorporated in the analysis, it may lead, in some cases, to phenomenologically inconsistent results.

We reexamine the issue of singularity resolution in homogeneous loop quantum cosmology from the perspective of geometrical entities such as expansion rate and the shear scalar. These quantities are very reliable measures of the properties of spacetime and can be defined not only at the classical and effective level, but also at an operator level in the quantum theory. From their behavior in the effective constraint surface and in the effective loop quantum spacetime, we show that one can severely restrict the ambiguities in regularization of the quantum constraint and rule out unphysical choices. We analyze this in the flat isotropic model and the Bianchi-I spacetimes. In the former case we show that the expansion rate is absolutely bounded only for the so-called improved quantization, a result which synergizes with uniqueness of this quantization as proved earlier. Surprisingly, for the Bianchi-I spacetime, we show that out of the available choices, the expansion rate and shear are bounded for only one regularization of the quantum constraint. It turns out that only for this choice, the theory exhibits quantum gravity corrections at a unique scale, and is physically viable.

We study the light deflection effect and the relativistic periastron and frame-dragging precessions for a rotating black hole localized on the brane in the Randall-Sundrum braneworld scenario. Focusing on a light ray, which passes through the field of the black hole in its equatorial plane, we first calculate the deflection angle in the weak field limit. We obtain an analytical formula, involving the related perturbative parameters of the field up to the second order. We then proceed with the numerical calculation of the deflection angle in the strong field limit when the light ray passes at the closest distance of approach to the limiting photon orbit. We show that the deflection angles for the light ray, winding maximally rotating Kerr and braneworld black holes in the same direction as their rotation, become essentially indistinguishable from each other for a specific value of the negative tidal charge. The same feature occurs in the relativistic precession frequencies at characteristic radii, for which the radial epicyclic frequency of the test particle motion attains its highest value. These results show that to distinguish between these two types of black holes one also needs to know the precise value of the angular momentum from independent observations, which for a maximally rotating braneworld black hole must exceed the Kerr bound in general relativity.

In transforming from Schwarzschild to Euclidean Rindler coordinates the Schwarzschild time transforms to a periodic angle. As is well-known, this allows one to introduce the Hawking temperature and is an origin of black hole thermodynamics. On the other hand, according to quantum mechanics this angle is conjugate to the $z$ component of the angular momentum. From the commutation relation and quantization condition for the angular momentum component it is found that the area of the horizon of a Schwarzschild black hole is quantized with the quantum $\Delta A=8\pi l_P^2$. It is shown that this conclusion is also valid for a generic Kerr-Newman black hole.

Recently, a renormalizable gravity theory with higher spatial derivatives in four dimensions was proposed by Hořava. The theory reduces to Einstein gravity with a nonvanishing cosmological constant in IR, but it has improved UV behaviors. The spherically symmetric black hole solutions for an arbitrary cosmological constant, which represent the generalization of the standard Schwarzschild–(anti) de Sitter solution, have also been obtained for the Hořava-Lifshitz theory. The exact asymptotically flat Schwarzschild-type solution of the gravitational field equations in Hořava gravity contains a quadratic increasing term, as well as the square root of a fourth order polynomial in the radial coordinate, and it depends on one arbitrary integration constant. The IR-modified Hořava gravity seems to be consistent with the current observational data, but in order to test its viability more observational constraints are necessary. In the present paper we consider the possibility of observationally testing Hořava gravity by using the accretion disk properties around black holes. The energy flux, the temperature distribution, the emission spectrum, as well as the energy conversion efficiency are obtained, and compared to the standard general relativistic case. Particular signatures can appear in the electromagnetic spectrum, thus leading to the possibility of directly testing Hořava gravity models by using astrophysical observations of the emission spectra from accretion disks.

We compute in detail the rate at which energy injected by dark matter (DM) annihilation heats and ionizes the photon-baryon plasma at $z\sim 1000$, and provide accurate fitting functions over the relevant redshift range for a broad array of annihilation channels and DM masses. The resulting perturbations to the ionization history can be constrained by measurements of the CMB temperature and polarization angular power spectra. We show that models which fit recently measured excesses in 10–1000 GeV electron and positron cosmic rays are already close to the 95% confidence limits from WMAP. The recently launched Planck satellite will be capable of ruling out a wide range of DM explanations for these excesses. In models of dark matter with Sommerfeld-enhanced annihilation, where $⟨\sigma v⟩$ rises with decreasing WIMP velocity until some saturation point, the WMAP5 constraints imply that the enhancement must be close to saturation in the neighborhood of the Earth.

We propose to test the dark matter (DM) interpretation of the positron excess observed by the PAMELA cosmic-ray (CR) detector through the identification of a Galactic diffuse gamma-ray component associated to DM-induced prompt and radiative emission. The goal is to present an analysis based on minimal sets of assumptions and extrapolations with respect to locally testable or measurable quantities. We discuss the differences between the spatial and spectral features for the DM-induced components (with an extended, possibly spherical, source function) and those for the standard CR contribution (with sources confined within the stellar disc), and propose to focus on intermediate and large latitudes. We address the dependence of the signal to background ratio on the model adopted to describe the propagation of charged CRs in the Galaxy, and find that, in general, the DM-induced signal can be detected by the Fermi Gamma-ray Space Telescope at energies above 100 GeV. An observational result in agreement with the prediction from standard CR components only, would imply very strong constraints on the DM interpretation of the PAMELA excess. On the other hand, if an excess in the diffuse emission above 100 GeV is identified, the angular profile for such emission would allow for a clean disentanglement between the DM interpretation and astrophysical explanations proposed for the PAMELA excess. We also compare to the radiative diffuse emission at lower frequencies, sketching, in particular, the detection prospects at infrared frequencies with the Planck satellite.

This article examines how breaking a Lorentz-invariant description of nature at tiny space-time intervals would affect the non-Gaussian character of the pattern of primordial perturbations left by inflation. We specifically study a set of irrelevant operators that preserve the spatial symmetries of the usual inflationary background. The non-Gaussian component in the primordial fluctuations can be much larger than the usual, small, inflationary prediction and can thus lead to much stronger constraints on the role of “trans-Planckian” physics in inflation than those from the measurements of the primordial power spectrum.

The $f(R)$ gravity models proposed by Hu-Sawicki and Starobinsky are generic for local gravity constraints to be evaded. The large deviations from these models result in either violation of local gravity constraints or the modifications indistinguishable from cosmological constant. The curvature singularity in these models is generic but can be avoided, provided that proper fine-tuning is imposed on the evolution of scalaron in the high curvature regime. In principle, the problem can be circumvented by incorporating quadratic curvature correction in the Lagrangian, though it might be quite challenging to probe the relevant region numerically.

Cosmic microwave background experiments must achieve very accurate calibration of their polarization reference frame to avoid biasing the cosmological parameters. In particular, a wrong or inaccurate calibration might mimic the presence of a gravitational wave background, or a signal from cosmological birefringence, a phenomenon characteristic of several nonstandard, symmetry breaking theories of electrodynamics that allow for in vacuo rotation of the polarization direction of the photon. Noteworthly, several authors have claimed that the BOOMERanG 2003 (B2K) published polarized power spectra of the cosmic microwave background may hint at cosmological birefringence. Such analyses, however, do not take into account the reported calibration uncertainties of the BOOMERanG focal plane. We develop a formalism to include this effect and apply it to the BOOMERanG dataset, finding a cosmological rotation angle $\alpha =-4.3°\pm 4.1°$. We also investigate the expected performances of future space borne experiment, finding that an overall miscalibration larger then 1° for Planck and 0.2° for the Experimental Probe of Inflationary Cosmology, if not properly taken into account, will produce a bias on the constraints on the cosmological parameters and could misleadingly suggest the presence of a gravitational waves background.

A generalized parametrization $w_{\beta }(z)$ for the dark energy equation of state is proposed and some of its cosmological consequences are investigated. We show that in the limit of the characteristic dimensionless parameter $\beta \to +1$, 0 and $-1$ some well-known equation of state parametrizations are fully recovered whereas for other values of $\beta$ the proposed parametrization admits a wider and new range of cosmological solutions. We also discuss possible constraints on the $w_{\beta }(z)$ parameters from current observational data.

In this paper we study the generation of primordial perturbations with a modified dispersion relation in various cosmological evolution scenarios. We stress that the formation of the power spectrum is strongly dependent on the background. By parameterizing a modified dispersion relation, we have listed all potential conditions on background evolution in order to seed scale-invariant primordial spectra. Working in a bounce model with a matterlike contracting phase, we obtain a red-tilted spectrum due to the modified dispersion relation.