Reliable values of quark and lepton masses are important for model building at a fundamental energy scale, such as the Fermi scale $M_Z\approx 91.2\mathrm{GeV}$ and the would-be GUT scale ${\Lambda }_{\mathrm{GUT}}\sim 2\times {10}^{16}\mathrm{GeV}$. Using the latest data given by the Particle Data Group, we update the running quark and charged-lepton masses at a number of interesting energy scales below and above $M_Z$. In particular, we take into account the possible new physics scale ($\mu \sim 1\mathrm{TeV}$) to be explored by the CERN LHC and the typical seesaw scales ($\mu \sim {10}^9\mathrm{GeV}$ and $\mu \sim {10}^{12}\mathrm{GeV}$) which might be relevant to the generation of neutrino masses. For illustration, the running masses of three light Majorana neutrinos are also calculated. Our up-to-date tables of running fermion masses are expected to be very useful for the study of flavor dynamics at various energy scales.

Neutrino oscillations data indicates that neutrino mixings are consistent with an apparent ${\nu }_{\mu }-{\nu }_{\tau }$ exchange symmetry in neutrino mass matrix. We observe that in the minimally extended standard model with the seesaw mechanism, one can impose $\mu \leftrightarrow \tau$ symmetry at the tree level on all Lagrangian terms, but for the mass difference among $\mu$ and $\tau$ leptons. In the absence of any new extra physics, this mass difference becomes the only source for the breaking of such a symmetry, which induces, via quantum corrections, small but predictable values for ${\theta }_{13}$, and for the deviation of ${\theta }_{\mathrm{ATM}}$ from maximality. In the $CP$ conserving case, the predictions only depend on neutrino mass hierarchy and may provide a unique way to test for new physics with neutrino experiments.

We present a study of the decay $B^{-}\to D_{(CP)}^0{K}^{-}$ and its charge conjugate, where $D_{(CP)}^0$ is reconstructed in both a non-$CP$ flavor eigenstate and in $CP$ ($CP$-even and $CP$-odd) eigenstates, based on a sample of 382 million ${\rm Y}(4S)\to B\overline{B}$ decays collected with the BABAR detector at the PEP-II $e^{+}{e}^{-}$ storage ring. We measure the direct $CP$ asymmetries $A_{CP\pm }$ and the ratios of the branching fractions $R_{CP\pm }$: $A_{CP+}=0.27\pm 0.09(\mathrm{stat})\pm 0.04(\mathrm{syst})$, $A_{CP-}=-0.09\pm 0.09(\mathrm{stat})\pm 0.02(\mathrm{syst})$, $R_{CP+}=1.06\pm 0.10(\mathrm{stat})\pm 0.05(\mathrm{syst})$, $R_{CP-}=1.03\pm 0.10(\mathrm{stat})\pm 0.05(\mathrm{syst})$. We also express the results in terms of the so-called Cartesian coordinates $x_{+}$, $x_{-}$, and $r^2$: $x_{+}=-0.09\pm 0.05(\mathrm{stat})\pm 0.02(\mathrm{syst})$, $x_{-}=0.10\pm 0.05(\mathrm{stat})\pm 0.03(\mathrm{syst})$, $r^2=0.05\pm 0.07(\mathrm{stat})\pm 0.03(\mathrm{syst})$. These results will help to better constrain the phase parameter $\gamma =\arg (-V_{ud}{V}_{ub}^{*}/V_{cd}{V}_{cb}^{*})$ of the Cabibbo-Kobayashi-Maskawa quark mixing matrix.

The addition of an adjoint Polyakov loop term to the action of a pure gauge theory at finite temperature leads to new phases of $SU(N)$ gauge theories. For $SU(3)$, a new phase is found which breaks $Z(3)$ symmetry in a novel way; for $SU(4)$, the new phase exhibits spontaneous symmetry breaking of $Z(4)$ to $Z(2)$, representing a partially-confined phase in which quarks are confined, but diquarks are not. The overall phase structure and thermodynamics is consistent with a theoretical model of the effective potential for the Polyakov loop based on perturbation theory.

We discuss the implications for gravitational wave detectors of a class of modified gravity theories which dispense with the need for dark matter. These models, which are known as dark matter emulators, have the property that weak gravitational waves couple to the metric that would follow from general relativity without dark matter whereas ordinary particles couple to a combination of the metric and other fields which reproduces the result of general relativity with dark matter. We show that there is an appreciable difference in the Shapiro delays of gravitational waves and photons or neutrinos from the same source, with the gravitational waves always arriving first. We compute the expected time lags for GRB 070201, for SN 1987a and for Sco-X1. We estimate the probable error by taking account of the uncertainty in position, and by using three different dark matter profiles.

We analyze the origin of the quasiclassical realm from the no-boundary proposal for the Universe’s quantum state in a class of minisuperspace models. The models assume homogeneous, isotropic, closed spacetime geometries, a single scalar field moving in a quadratic potential, and a fundamental cosmological constant. The allowed classical histories and their probabilities are calculated to leading semiclassical order. For the most realistic range of parameters analyzed, we find that a minimum amount of scalar field is required, if there is any at all, in order for the Universe to behave classically at late times. If the classical late time histories are extended back, they may be singular or bounce at a finite radius. The ensemble of classical histories is time symmetric although individual histories are generally not. The no-boundary proposal selects inflationary histories, but the measure on the classical solutions it provides is heavily biased towards small amounts of inflation. However, the probability for a large number of e-foldings is enhanced by the volume factor needed to obtain the probability for what we observe in our past light cone, given our present age. Our results emphasize that it is the quantum state of the Universe that determines whether or not it exhibits a quasiclassical realm and what histories are possible or probable within that realm.

We assess the effects of a collision between two vacuum bubbles in the thin-wall limit. After describing the outcome of a generic collision possessing the expected hyperbolic symmetry, we focus on collisions experienced by a bubble containing positive vacuum energy, which could in principle contain our observable universe. We provide criteria governing whether the post-collision domain wall accelerates towards or away from this observation bubble, and discuss the implications for observers located at various positions inside of the bubble. Then, we identify the class of solutions which have minimal impact on the interior of the observation bubble, and derive a simple formula for the energy density of a shell of radiation emitted from such a collision. In the context of a universe undergoing false-vacuum eternal inflation, these solutions are perhaps the most promising candidates for collisions that could exist within our past light cone, and therefore in principle be observable.

We calculate the stress tensor, or energy-momentum tensor, form factors of the pion and of axial-vector mesons in the chiral limit of a hard-wall AdS/conformal-field-theory model of QCD. One (of the two) pion gravitational form factors is directly related to the second moment of the pion generalized parton distribution, thus providing a sum rule for the latter. As was also the case for vector mesons, both the pion and the axial-vector mesons appear strikingly more compact measured by the gravitational form factor than by the electromagnetic form factor.

We analyze the lepton sector of the left-right twin Higgs model. This model offers an alternative way to solve the “little hierarchy” problem of the standard model. We show that one can achieve an effective seesaw to explain the origin of neutrino masses and that this model can accommodate the observed neutrino masses and mixings. We have also studied the lepton flavor violation process ${\ell }_i\to {\ell }_j\gamma$ and discussed how the experimental bound from these branching ratios constrains the scale of symmetry breaking of this twin Higgs model.

Dynamics of $\mathrm{SU}(N_c)$ Yang-Mills theories with $N_f$ adjoint Weyl fermions is quite different from that of $\mathrm{SU}(N_c)$ gauge theories with fundamental quarks. The symmetry breaking pattern is $\mathrm{SU}(N_f)\to \mathrm{SO}(N_f)$. The corresponding sigma model supports Skyrmions whose microscopic identification is not immediately clear. We address this issue as well as the issue of the Skyrmion stability. The case of $N_f=2$ had been considered previously. Here we discuss $N_f\ge 3$. We discuss the coupling between the massless Goldstone bosons and massive composite fermions [with mass $\mathrm{O}(N_c^0)$] from the standpoint of the low-energy chiral sigma model. We derive the Wess-Zumino-Novikov-Witten term and then determine Skyrmion statistics. We also determine their fermion number (mod 2) and observe an abnormal relation between the statistics and the fermion number. This explains the Skyrmion stability. In addition, we consider another microscopic theory—$\mathrm{SO}(N_c)$ Yang-Mills with $N_f$ Weyl fermions in the vectorial representation—which has the same chiral symmetry breaking pattern and the same chiral Lagrangian. We discuss distinctive features of these two scenarios.

We study the vibration modes of the Skyrme model within the rational map ansatz. We show that the vibrations of the radial profiles and the rational maps are decoupled and we consider explicitly the cases $B=1$, $B=2$, and $B=4$. We then compare our results with the vibration modes obtained numerically by Barnes et al. and show that qualitatively the rational map reproduces the vibration modes obtained numerically but that the vibration frequencies of these modes do not match very well.

The field theoretic action for gravitational interactions in $d+2$ dimensions is constructed in the formalism of two-time (2T) physics. General relativity in $d$ dimensions emerges as a shadow of this theory with one less time and one less space dimensions. The gravitational constant turns out to be a shadow of a dilaton field in $d+2$ dimensions that appears as a constant to observers stuck in $d$ dimensions. If elementary scalar fields play a role in the fundamental theory (such as Higgs fields in the standard model coupled to gravity), then their shadows in $d$ dimensions must necessarily be conformal scalars. This has the physical consequence that the gravitational constant changes at each phase transition (inflation, grand unification, electroweak, etc.), implying interesting new scenarios in cosmological applications. The fundamental action for pure gravity, which includes the spacetime metric $G_{MN}(X)$, the dilaton $\Omega (X)$, and an additional auxiliary scalar field $W(X)$, all in $d+2$ dimensions with two times, has a mix of gauge symmetries to produce appropriate constraints that remove all ghosts or redundant degrees of freedom. The action produces on-shell classical field equations of motion in $d+2$ dimensions, with enough constraints for the theory to be in agreement with classical general relativity in $d$ dimensions. Therefore this action describes the correct classical gravitational physics directly in $d+2$ dimensions. Taken together with previous similar work on the standard model of particles and forces, the present paper shows that 2T physics is a general consistent framework for a physical theory. Furthermore, the 2T-physics approach reveals more physical information for observers stuck in the shadow in $d$ dimensions in the form of hidden symmetries and dualities, that are largely concealed in the usual one-time formulation of physics.

It is well known that there are no static non-Abelian monopole solutions in pure Yang-Mills theory on Minkowski space ${\mathbb{R}}^{3,1}$. I show that such solutions exist in $\mathrm{SU}(N)$ gauge theory on the spaces ${\mathbb{R}}^2\times S^2$ and $\mathbb{R}\times S^1\times S^2$ with Minkowski signature $(-+++)$. In the temporal gauge they are solutions of pure Yang-Mills theory on $\mathbb{T}\times S^2$, where $\mathbb{T}$ is $\mathbb{R}$ or $S^1$. Namely, imposing SO(3) invariance and some reality conditions, I consistently reduce the Yang-Mills model on the above spaces to a non-Abelian analog of the ${\varphi }^4$ kink model whose static solutions give $\mathrm{SU}(N)$ monopole (-antimonopole) configurations on the space ${\mathbb{R}}^{1,1}\times S^2$ via the above-mentioned correspondence. These solutions can also be considered as instanton configurations of Yang-Mills theory in $2+1$ dimensions. The kink model on $\mathbb{R}\times S^1$ admits also periodic sphaleron-type solutions describing chains of $n$ kink-antikink pairs spaced around the circle $S^1$ with arbitrary $n>0$. They correspond to chains of $n$ static monopole-antimonopole pairs on the space $\mathbb{R}\times S^1\times S^2$ which can also be interpreted as instanton configurations in $2+1$ dimensional pure Yang-Mills theory at finite temperature (thermal time circle). I also describe similar solutions in Euclidean $\mathrm{SU}(N)$ gauge theory on $S^1\times S^3$ interpreted as chains of $n$ instanton–anti-instanton pairs.

We discuss “spectral-flow” coordinate transformations that take asymptotically four-dimensional solutions into other asymptotically four-dimensional solutions. We find that spectral flow can relate smooth three-charge solutions with a multicenter Taub-NUT base to solutions where one or several Taub-NUT centers are replaced by two-charge supertubes, and vice versa. We further show that multiparameter spectral flows can map such Taub-NUT centers to more singular centers that are either D2-D0 or pure D0-brane sources. Since supertubes can depend on arbitrary functions, we establish that the moduli space of smooth horizonless black-hole microstate solutions is classically of infinite dimension. We also use the physics of supertubes to argue that some multicenter solutions that appear to be bound states from a four-dimensional perspective are in fact not bound states when considered from a five- or six-dimensional perspective.

We study the tetrad formulation of Chern-Simons (CS) modified gravity, which adds a Pontryagin term to the Einstein-Hilbert action with a spacetime-dependent coupling field. We first verify that CS modified gravity leads to a theory with torsion, where this tensor is given by an antisymmetric product of the Riemann tensor and derivatives of the CS coupling. We then calculate the torsion in the far field of a weakly gravitating source within the parameterized post-Newtonian formalism, and specialize the result to Earth. We find that CS torsion vanishes only if the coupling vanishes, thus generically leading to a modification of gyroscopic precession, irrespective of the coupling choice. Perhaps most interestingly, we couple fermions to CS modified gravity via the standard Dirac action and find that these further correct the torsion tensor. Such a correction leads to two new results: (i) a generic enhancement of CS modified gravity by the Dirac equation and axial fermion currents; (ii) a new two-fermion interaction, mediated by an axial current and the CS correction. We conclude with a discussion of the consequences of these results in particle detectors and realistic astrophysical systems.

In this paper we consider general relativity and its combination with scalar quantum electrodynamics (QED) as an effective quantum field theory at energies well below the Planck scale. This enables us to compute the one-loop quantum corrections to the Newton and Coulomb potentials induced by the combination of graviton and photon fluctuations. We derive the relevant Feynman rules and compute the nonanalytical contributions to the one-loop scattering matrix for charged scalars in the nonrelativistic limit. In particular, we derive the post-Newtonian corrections of order $Gm/{\mathrm{c}}^{2}r$ from general relativity and the genuine quantum corrections of order $G\hslash /{\mathrm{c}}^3{r}^2$.

We propose a $4+1$-dimensional action that is a candidate for realizing a standard-model-like effective theory for fields dynamically localized to a domain-wall brane. Our construction is in part based on the conjecture that the Dvali-Shifman mechanism for dynamically localizing gauge bosons to a domain wall works correctly in $4+1\mathrm{\text{−}}\mathrm{d}$. Assuming this to be so, we require the gauge symmetry to be SU(5) in the bulk, spontaneously breaking to $\mathrm{SU}(3)\otimes \mathrm{SU}(2)\otimes \mathrm{U}(1)$ inside the domain wall, thus dynamically localizing the standard-model gauge bosons provided that the SU(5) theory in the bulk exhibits confinement. The wall is created jointly by a real singlet-Higgs field $\eta$ configured as a kink, and an SU(5) adjoint-Higgs field $\chi$ that takes nonzero values inside the wall. Chiral $3+1$-dimensional quarks and leptons are confined and split along the bulk direction via their Yukawa couplings to $\eta$ and $\chi$. The Higgs doublet and its color triplet SU(5) partner are similarly localized and split. The splittings can suppress colored-Higgs-induced proton decay and, because of the different localization profiles, the usual SU(5) mass relation $m_e=m_d$ does not arise. Localized gravity is generated via the Randall-Sundrum alternative to compactification.

Inflation driven by a single dark spinor field is discussed. We define the notion of a dark spinor field and derive the cosmological field equations for such a matter source. The conditions for inflation are determined and an exactly solvable model is presented. We find the power spectrum of the quantum fluctuation of this field and compare the results with scalar field inflation.

We argue that Einstein gravity coupled to a Born-Infeld theory provides an attractive candidate to represent dark matter and dark energy. For cosmological models, the Born-Infeld field has an equation of state which interpolates between matter, $p=0$ (small times), and a cosmological constant $p=-\rho$ (large times). On galactic scales, the Born-Infeld theory predicts asymptotically flat rotation curves.

Is Newton’s gravity sufficient to handle the weakly nonlinear evolution stages of the large-scale cosmic structures? Here we resolve the issue by analytically deriving the density and velocity power spectra to the second order in the context of Einstein’s gravity. The recently found pure general relativistic corrections appearing in the third-order perturbation contribute to power spectra to the second order. In this work the complete density and velocity power spectra to the second order are derived. The power transfers among different scales in the density power spectrum are estimated in the context of Einstein’s gravity. The relativistic corrections in the density power spectrum are estimated to be smaller than the Newtonian one to the second order, but these could be larger than higher-order nonlinear Newtonian terms.