In this paper we introduce a simple renormalizable model of an extended color gauge sector in which the third-generation quarks couple differently than the lighter quarks. In addition to a set of heavy color-octet vector bosons (colorons), the model also contains a set of heavy weak vector quarks. Mixing between the third generation of quarks and the first two is naturally small and occurs only through the (suppressed) mixing of all three generations with the heavy vector quarks. We discuss the constraints on this model arising from limits on flavor-changing neutral currents and from collider searches for the colorons and vector quarks, and discuss the prospects for discovery at the LHC.

The $s$-wave pion-pion ($\pi \pi$) scattering lengths are computed below the inelastic threshold by the Lüscher technique with pion masses ranging from 240 to 463 MeV. In the Asqtad-improved staggered fermion formulation, we calculate the $\pi \pi$ four-point functions for the $I=0$ and 2 channels with “moving” wall sources without gauge fixing, and we analyze them at the next-to-leading order in the continuum three-flavor chiral perturbation theory. At the physical pion mass, we secure the $s$-wave $\pi \pi$ scattering lengths as $m_{\pi }{a}_{\pi \pi }^{I=0}=0.214(4)(7)$ and $m_{\pi }{a}_{\pi \pi }^{I=2}=-0.04430(25)(40)$ for the $I=0$ and 2 channels, respectively, where the first uncertainties are statistical and the second ones are our estimates of several systematic effects. Our lattice results for the $s$-wave $\pi \pi$ scattering lengths are in good accordance with available experimental reports and theoretical forecasts at low momentum. A basic ingredient in our study for the $I=0$ case is properly incorporating the disconnected diagram. These lattice computations are carried out with the MILC $2+1$ flavor gauge configurations at two lattice spacings, $a\approx 0.15$ and 0.12 fm.

A difference of several tenths of a percent has been observed between the direct $CP$ asymmetries of $D^0\to K^{+}{K}^{-}$ and $D^0\to {\pi }^{+}{\pi }^{-}$. It has been noted recently that $CP$ asymmetries in such singly Cabibbo-suppressed decays can affect the determination of the weak phase $\gamma$ using the Gronau-London-Wyler method of comparing rates for $B^{+}\to D{K}^{+}$ and $B^{-}\to D{K}^{-}$, where $D$ is a superposition of $D^0$ and ${\overline{D}}^0$ decaying to a $CP$ eigenstate. Using an analysis of the $CP$ asymmetries in singly Cabibbo-suppressed decays based on a $c\to u$ penguin amplitude with a standard model weak phase but enhanced by $CP$-conserving strong interactions, we estimate typical shifts in $\gamma$ of several degrees and pinpoint measurements which would reduce uncertainties to an acceptable level.

We extend a previous analysis of the lowest-lying octet baryon masses in covariant baryon chiral perturbation theory by explicitly taking into account the contribution of the virtual decuplet baryons. Up to next-to-next-to-next-to-leading order, the effects of these heavier degrees of freedom are systematically studied. Their effects on the light-quark mass dependence of the octet baryon masses are shown to be relatively small and can be absorbed by the available low-energy constants up to next-to-next-to-next-to-leading order. Nevertheless, a better description of the finite-volume corrections of the lattice QCD data can be achieved, particularly those with small $M_{\varphi }L$ ($<4$), which is demonstrated by a careful study of the NPLQCD and QCDSF-UKQCD small-volume data. Finally, we show that the predicted pion- and strangeness-baryon sigma terms are only slightly changed by the inclusion of the virtual decuplet baryons.

The magnetic moment and vanishing charge of a Dirac neutrino are physically observable quantities and must not depend on the choice of gauge in a consistent quantum field theory. We verify this statement explicitly at the one-loop level in both $R_{\xi }$ and unitary gauges of the minimally extended standard model. We accomplish this by manipulating directly the integrands of loop integrals and employing simple algebraic identities and integral relations. Our result generally applies for any masses of the relevant particles and unitary neutrino mixing.

In this paper, a search for supersymmetry (SUSY) is presented in events with two opposite-sign isolated leptons in the final state, accompanied by hadronic jets and missing transverse energy. An artificial neural network is employed to discriminate possible SUSY signals from a standard model background. The analysis uses a data sample collected with the CMS detector during the 2011 LHC run, corresponding to an integrated luminosity of $4.98{\mathrm{fb}}^{-1}$ of proton-proton collisions at the center-of-mass energy of 7 TeV. Compared to other CMS analyses, this one uses relaxed criteria on missing transverse energy (${\mathrm{E̸}}_{\mathrm{T}}>40\mathrm{GeV}$) and total hadronic transverse energy ($H_{\mathrm{T}}>120\mathrm{GeV}$), thus probing different regions of parameter space. Agreement is found between standard model expectation and observations, yielding limits in the context of the constrained minimal supersymmetric standard model and on a set of simplified models.

We construct a stable domain wall ring with lump beads on it in a baby Skyrme model with a potential consisting of two terms linear and quadratic in fields.

The Weyl fermions with a well defined chirality are known to demand that the dimension of space which they inhabit must be odd. It is shown here, however, that not all odd dimensional spaces are equally good hosts: in particular, an arbitrary number of chiral Weyl fermions can acquire a Majorana type of mass only in three (modulo eight) dimensions. The argument utilizes (a) the precise analogy between the Majorana mass term and the coupling of time-reversed Weyl fermions, and (b) the conditions on the requisite time reversal operator, which are implied by the real representations of Clifford algebras. In particular, it is shown that the latter allows only an even number of Majorana-massive Weyl fermions in seven (modulo eight) spatial dimensions. The theorem connects the observed odd number of neutrino flavors, the time reversal symmetry, and the dimension of our space and strengthens the argument for the possible violation of the lepton number conservation law.

The sampled negative energy density seen by inertial observers, in arbitrary quantum states is limited by quantum inequalities, which take the form of an inverse relation between the magnitude and duration of the negative energy. The quantum inequalities severely limit the utilization of negative energy to produce gross macroscopic effects, such as violations of the second law of thermodynamics. The restrictions on the sampled energy density along the worldlines of accelerated observers are much weaker than for inertial observers. Here we will illustrate this with several explicit examples. We consider the worldline of a particle undergoing sinusoidal motion in space in the presence of a single mode squeezed vacuum state of the electromagnetic field. We show that it is possible for the integrated energy density along such a worldline to become arbitrarily negative at a constant average rate. Thus the averaged weak energy condition is violated in these examples. This can be the case even when the particle moves at nonrelativistic speeds. We use the Raychaudhuri equation to show that there can be net defocusing of a congruence of these accelerated worldlines. This defocusing is an operational signature of the negative integrated energy density. These results in no way invalidate nor undermine either the validity or utility of the quantum inequalities for inertial observers. In particular, they do not change previous constraints on the production of macroscopic effects with negative energy, e.g., the maintenance of traversable wormholes.

We construct a new class of perturbative extremal charged rotating black hole solutions in five dimensions in the Einstein-Born-Infeld theory. We start with an extremal five-dimensional Myers-Perry black hole seed in which the two possible angular momenta have equal magnitude, and add a Born-Infeld electrical charge, keeping the extremality condition as a constraint. The perturbative parameter is assumed to be the electric charge $q$ and the perturbations are performed up to fourth order. We also study some physical properties of these black holes. It is shown that the perturbative parameter $q$ and the Born-Infeld parameter $\beta$ modify the values of the physical quantities of the black holes. The solution suggests that the magnetic moment and gyromagnetic ratio of the black hole spacetime change sign when the Born-Infeld character of the solution starts to depart strongly from the Maxwell limit. We venture an interpretation for the effect.

The zeroth principle of thermodynamics in the form “temperature is uniform at equilibrium” is notoriously violated in relativistic gravity. Temperature uniformity is often derived from the maximization of the total number of microstates of two interacting systems under energy exchanges. Here we discuss a generalized version of this derivation, based on informational notions, which remains valid in the general context. The result is based on the observation that the time taken by any system to move to a distinguishable (nearly orthogonal) quantum state is a universal quantity that depends solely on the temperature. At equilibrium the net information flow between two systems must vanish, and this happens when two systems transit the same number of distinguishable states in the course of their interaction.

We discuss how one can reconstruct the thermal history of the Universe by combining cosmic microwave background (CMB) measurements and gravitational wave (GW) direct detection experiments. Assuming various expansion eras to take place after the inflationary reheating and before big bang nucleosynthesis, we show how measurements of the GW spectrum can be used to break the degeneracies associated with CMB data, the latter being sensitive to the total amount of cosmic expansion only. In this context, we argue that the expected constraints from future CMB and GW experiments can probe a scenario in which there exists late-time entropy production in addition to the standard reheating. We show that, for some cases, combining data from future CMB and GW direct detection experiments allows the determination of the reheating temperature, the amount of entropy produced and the temperature at which the standard radiation era started.

Typically, the fluctuations generated from a decaying field during inflation do not contribute to the large scale structures. In this paper, we provide an example where it is possible for a field which slowly rolls and then decays during inflation to create all the matter perturbations with a slightly red-tilted spectral index, with no isocurvature perturbations, and with a possibility of a departure from Gaussian fluctuations.

Following the renewed interest in the topic [Halliwell and Yearsley, Phys. Rev. D 86, 024016 (2012)], we revisit the problem of assigning probabilities to classes of Feynman paths passing through specified space-time regions. We show that by assigning probabilities to interfering alternatives, one already makes the assumption that the interference has been destroyed through interacting with the environment or a meter. Including the effects of the meter allows one to construct a consistent theory, free of logical “pitfalls,” such as those identified in Halliwell and Yearsley. Wherever a meter cannot be constructed, or cannot be set to effect the desired decoherence, formally constructed probabilities have no clear physical meaning and can violate the necessary sum rules. We illustrate the above approach by analysing the three examples considered in Halliwell and Yearsley.

Motivated by the excess in the diphoton production rate of the Higgs boson at the Large Hadron Collider (LHC), we investigate the possibility that one of the $CP$-even Higgs bosons of the extra $U(1)$ extended minimal supersymmetric standard model can give a consistent result. We scan the parameter space for a standard-model-like Higgs boson such that the mass is in the range of 124–127 GeV and the production rate $\sigma B$ of the $W{W}^{*}$, $Z{Z}^{*}$ modes is consistent with the standard model (SM) values, while that of $\gamma \gamma$ is enhanced relative to the SM value. We find that the SM-like Higgs boson is mostly the lightest $CP$-even Higgs boson and it has a strong mixing with the second lightest one, which is largely singletlike. The implications on $Z\gamma$ production rate and properties of the other Higgs bosons are also studied.

A fundamental ingredient in wormhole physics is the flaring-out condition at the throat which, in classical general relativity, entails the violation of the null energy condition. In this work, we present the most general conditions in the context of modified gravity, in which the matter threading the wormhole throat satisfies all of the energy conditions, and it is the higher order curvature terms, which may be interpreted as a gravitational fluid, that support these nonstandard wormhole geometries. Thus, we explicitly show that wormhole geometries can be theoretically constructed without the presence of exotic matter but are sustained in the context of modified gravity.

We consider the electromagnetic and gravitational interactions of a massive Rarita-Schwinger field. Stückelberg analysis of the system, when coupled to electromagnetism in flat space or to gravity, reveals in either case that the effective field theory has a model-independent upper bound on its UV cutoff, which is finite but parametrically larger than the particle’s mass. It is the helicity-$1/2$ mode that becomes strongly coupled at the cutoff scale. If the interactions are inconsistent, the same mode becomes a telltale sign of pathologies. Alternatively, consistent interactions are those that propagate this mode within the light cone. Studying its dynamics not only sheds light on the Velo-Zwanziger acausality, but also elucidates why supergravity and other known consistent models are pathology-free.

$S$ matrices of $\mathcal{N}=2$, 4, 8 supersymmetric Yang-Mills theories in three spacetime dimensions (without matter hypermultiplets) are shown to be covariant under $SU(1|1)$, $SU(2|2)$ and $SU(2|2)\otimes SU(2|2)$, respectively. These symmetries are not manifest in the off-shell Lagrangian formulations of these theories. A possible connection between these symmetries and their representations in terms of the Yang-Mills degrees of freedom and the corresponding quantities in Chern-Simons matter theories with $\mathcal{N}\ge 4$ supersymmetry is presented. Dimensional reduction of the on-shell observables of the Yang-Mills theories to two spacetime dimensions is discussed.

We present a renormalization group analysis to Einstein-Rosen waves or vacuum spacetimes with whole-cylinder symmetry. It is found that self-similar solutions appear as fixed points in the renormalization group transformation. These solutions correspond to the explosive gravitational waves and the collapsing gravitational waves at late times and early times, respectively. Based on the linear perturbation analysis of the self-similar solutions, we conclude that the self-similar evolution is stable as explosive gravitational waves under the condition of no incoming waves, while it is weakly unstable as collapsing gravitational waves. The result implies that self-similar solutions can describe the asymptotic behavior of more general solutions for exploding gravitational waves and thus extends the similarity hypothesis in general relativity from spherical symmetry to cylindrical symmetry.

The luminosity distance describing the effect of local inhomogeneities in the propagation of light proposed by Zeldovich, Kantowski, Dyer, and Roeder is tested with two probes for two distinct ranges of redshifts: supernovae Ia in $0.015\le z\le 1.414$ and gamma-ray bursts in $1.547\le z\le 3.57$. Our analysis is performed by a Markov chain Monte Carlo code that allows us to constrain the matter density parameter ${\Omega }_m$ as well as the smoothness parameter $\alpha$ that measures the inhomogeneous-homogeneous rate of the cosmic fluid in a flat $\Lambda$ cold dark matter model. The obtained best fits are ${\Omega }_m={0.285}_{-0.018}^{+0.019}$, $\alpha ={0.856}_{-0.176}^{+0.106}$ from supernovae Ia, and ${\Omega }_m={0.259}_{-0.028}^{+0.028}$, $\alpha ={0.587}_{-0.202}^{+0.201}$ from gamma-ray bursts, while from the joint analysis the best fits are ${\Omega }_m={0.284}_{-0.020}^{+0.021}$, $\alpha ={0.685}_{-0.171}^{+0.164}$ with ${\chi }_{\mathrm{red}}^2=0.975$. The value of the smoothness parameter $\alpha$ indicates a clumped universe; however, it does not have an impact on the amount of dark energy (cosmological constant) needed to fit the observations. This result may be an indication that the Dyer-Roeder approximation does not describe in a precise form the effects of clumpiness in the expansion of the Universe.