Based on astrophysical constraints derived from Chandrasekhar’s mass limit for white dwarfs, we study the effects of the model on the parameters of unparticle-inspired gravity, on scales ${\Lambda }_U>1\mathrm{TeV}$ and $d_U\approx 1$.

We describe a class of supersymmetric models in which neutrinos are kept light by an $R$-symmetry. In supergravity, $R$-symmetry must be broken to allow for a small cosmological constant after supersymmetry breaking. In the class of models described here, this $R$-symmetry breaking results in the generation of Dirac neutrino masses, connecting the tuning of the cosmological constant to the puzzle of neutrino masses. Surprisingly, under the assumption of low-scale supersymmetry breaking and superpartner masses close to a TeV, these masses are independent of the fundamental supersymmetry-breaking scale, and accommodate the correct magnitude. This offers a novel explanation for the vastly different scales of neutrino and charged fermion masses. These models require that $R$-symmetric supersymmetry exists at the TeV scale, and predict that neutrino masses are purely Dirac, implying the absence of neutrinoless double $\beta$ decay. Interesting collider signals can arise due to charged scalars which decay leptonically, with branching ratios determined by the neutrino mixing matrix.

We generalize unitarity bounds on operator dimensions in conformal field theory to field theories with spacetime dependent couplings. Below the energy scale of spacetime variation of the couplings, their evolution can strongly affect the physics, effectively shifting the infrared operator scaling and unitarity bounds determined from correlation functions in the theory. We analyze this explicitly for large-$N$ double-trace flows, and connect these to UV complete field theories. One motivating class of examples comes from our previous work on Friedmann-Robertson-Walker holography, where this effect explains the range of flavors allowed in the dual, time-dependent field theory.

Localization of fermions is studied in different gravitational domain wall models. These are generalizations of the brane-world models considered by Randall and Sundrum, but which also allow gravitational localization. Therefore, they might be considered as possible realistic scenarios for phenomenology.

We construct a new class of higher-dimensional black hole solutions of $f(R)$ theory coupled to a nonlinear Maxwell field. In deriving these solutions the traceless property of the energy-momentum tensor of the matter filed plays a crucial role. In $n$-dimensional spacetime the energy-momentum tensor of conformally invariant Maxwell field is traceless provided we take $n=4p$, where $p$ is the power of conformally invariant Maxwell Lagrangian. These black hole solutions are similar to higher-dimensional Reissner-Nordstrom anti-de Sitter black holes but only exist for dimensions which are multiples of four. We calculate the conserved and thermodynamic quantities of these black holes and check the validity of the first law of black hole thermodynamics by computing a Smarr-type formula for the total mass of the solutions. Finally, we study the local stability of the solutions and find that there is indeed a phase transition for higher-dimensional $f(R)$ black holes with conformally invariant Maxwell source.

There is an observational indication of extragalactic magnetic fields. No known astrophysical process can explain the origin of such large scale magnetic fields, which motivates us to look for their origin in primordial inflation. By solving the linearized Einstein equations, we study metric perturbations sourced by magnetic fields that are produced during inflation. This leads to a simple but robust bound on the inflation models by requiring that the induced metric perturbation should not exceed the observed value ${10}^{-5}$. In the case of the standard single field inflation model, the bound can be converted into a lower bound on the Hubble parameter during inflation.

The difference between the vacuum energy of quantum fields in Minkowski space and in a Friedmann-Robertson-Walker universe might be related to the observed dark energy. The vacuum energy of the Veneziano ghost field introduced to solve the $U(1{)}_A$ problem in QCD is of the form $H+\mathcal{O}(H^2)$. Based on this, we study the dynamical evolution of a phenomenological dark energy model whose energy density is of the form $\alpha H+\beta H^2$. In this model, the universe approaches a de Sitter phase at late times. We fit the model with current observational data, including SnIa, BAO, CMB, BBN, the Hubble parameter, and the growth rate of matter perturbation. It shows that the universe begins to accelerate at redshift $z\sim 0.75$, and this model is consistent with current data. In particular, this model fits the data of the growth factor well as the $\Lambda \mathrm{CDM}$ model.

In many models, stability of dark-matter particles is protected by a conserved ${\mathbb{Z}}_2$ quantum number. However, dark matter can be stabilized by other discrete symmetry groups, and examples of such models with custom-tailored field content have been proposed. Here, we show that electroweak symmetry-breaking models with $N$ Higgs doublets can readily accommodate scalar dark matter candidates stabilized by groups ${\mathbb{Z}}_p$ with any $p\le 2^{N-1}$, leading to a variety of kinds of microscopic dynamics in the dark sector. We give examples in which semiannihilation or multiple semiannihilation processes are allowed or forbidden, which can be especially interesting in the case of asymmetric dark matter.

We consider neutron radiative $\beta$ decay, $n\to p{e}^{-}{\overline{\nu }}_e\gamma$, and compute the $T$-odd momentum correlation in the decay rate characterized by the kinematical variable $\xi ={\mathbf{l}}_{\nu }·({\mathbf{l}}_e\times \mathbf{k})$ arising from electromagnetic final-state interactions in the standard model. Our expression for the corresponding $T$-odd asymmetry $A_{\xi }^{\mathrm{SM}}$ is exact in $\mathcal{O}(\alpha )$ up to terms of recoil order, and we evaluate it numerically under various kinematic conditions. Noting the universality of the $V\mathrm{\text{−}}A$ law in the absence of recoil-order terms, we retain the parametric dependence on masses and coupling constants throughout, so that our results serve as a template for the computation of $A_{\xi }^{\mathrm{SM}}$ in allowed nuclear radiative $\beta$ decays and hyperon radiative $\beta$ decays as well.

The color fields in a system composed by two static quarks and two static antiquarks are studied. We use a variational method, to probe not only the ground state but also the first excited state. These results permit us to observe and interpret the flux tube recombination in the mesons-to-mesons and the tetraquark-to-mesons transitions, for both states. The results are compared with previous results for the static potential and the Casimir scaling predictions.

We derive the partition function for the SU(3) Yang-Mills theory in the presence of a uniform gluon field within the background field method. We show that the $n$-body gluon contributions in the partition function are characterized solely by the Polyakov loop. We express the effective action through characters of different representations of the color gauge group resulting in a form deduced in the strong-coupling expansion. A striking feature of this potential is that at low temperature gluons are physically disfavored, and therefore they do not yield the correct thermodynamics. We suggest a hybrid approach to Yang-Mills thermodynamics, combining the effective gluon potential with glueballs implemented as dilaton fields.

The Large Hadron Collider (LHC) recently started operating at 8 TeV. In this paper, we update our earlier LHC forward hadronic scattering predictions [Phys. Rep. 436, 71 (2006); Phys. Rev. D 83, 077901 (2011); Phys. Rev. Lett. 107, 212002 (2011)], giving new predictions, including errors, for the $pp$ total and inelastic cross sections, the $\rho$-value, the nuclear slope parameter $B$, $d{\sigma }_{\mathrm{el}}/dt$, and the large gap survival probability at 8 TeV.

In light of the recent neutrino experiment results from the Daya Bay and RENO Collaborations, we study phenomenology of neutrino mixing angles in the type III seesaw model with a discrete $A_4\times Z_2$ symmetry, whose spontaneously breaking scale is much higher than the electroweak scale. At tree level, the tri-bimaximal (TBM) form of the lepton mixing matrix can be obtained from leptonic Yukawa interactions in a natural way. We introduce all possible effective dimension-five operators, invariant under the standard model gauge group and $A_4\times Z_2$, and explicitly show that they induce a deviation of the lepton mixing from the TBM mixing matrix, which can explain a large mixing angle ${\theta }_{13}$ together with small deviations of the solar and atmospheric mixing angles from the TBM. Two possible scenarios are investigated, by taking into account either negligible or sizable contributions from the light charged lepton sector to the lepton mixing matrix. Especially it is found in the latter scenario that all the neutrino experimental data, including the recent best-fit value of ${\theta }_{13}=8.68°$, can be accommodated. The leptonic $CP$ violation characterized by the Jarlskog invariant $J_{CP}$ has a nonvanishing value, indicating a signal of maximal $CP$ violation.

We propose a new seesaw model based on a fermionic hypercharge-zero weak quintuplet in conjunction with an additional scalar quadruplet which attains an induced vacuum expectation value. The model provides both tree-level seesaw $\sim v^6/M^5$ and loop-suppressed radiative $\sim (1/16{\pi }^2)·v^2/M$ contributions to active neutrino masses. The empirical masses $m_{\nu }\sim {10}^{-1}\mathrm{eV}$ can be achieved with $M\sim \mathrm{TeV}$ new states, accessible at the LHC. For $5{\mathrm{fb}}^{-1}$ of accumulated integrated luminosity at the LHC, there could be $\sim 500$ doubly-charged ${\Sigma }^{++}$ or $\overline{{\Sigma }^{++}}$ fermions with mass $M_{\Sigma }=400\mathrm{GeV}$, leading to interesting multilepton signatures. The neutral component of the fermion quintuplet, previously identified as a minimal dark matter candidate, becomes unstable in the proposed seesaw setup. The stability can be restored by introducing a $Z_2$ symmetry, in which case neutrinos get mass only from radiative contributions.

We point out that the recent Belle measurements of the $B_{d/s}\to J/\psi {\eta }^{(\prime )}$ decays imply large pseudoscalar glueball contents in the ${\eta }^{(\prime )}$ meson. These decays are studied in the perturbative QCD approach, considering the $\eta$-${\eta }^{\prime }$-$G$ mixing, where $G$ represents the pseudoscalar glueball. We show that the perturbative QCD predictions for the $B_{d/s}\to J/\psi {\eta }^{(\prime )}$ branching ratios agree well with the data for the mixing angle ${\varphi }_G\approx 30°$ between the flavor-singlet state and the pure pseudoscalar glueball. Extending the formalism to the $\eta$-${\eta }^{\prime }$-$G$-${\eta }_c$ tetramixing, the abnormally large observed $B_d\to K{\eta }^{\prime }$ branching ratios are also explained. The proposed mixing formalism is applicable to other heavy meson decays into ${\eta }^{(\prime )}$ mesons, and could be tested by future LHC beauty experiments and Super-$B$ factory data.

We study the relationship between charge density ($\rho$) and chemical potential ($\mu$) for an array of Lorentz-invariant $3+1$-dimensional holographic field theories with the minimal structure of a conserved charge. In all cases, at large density, the relationship is well-modeled by a power-law behavior of the form $\rho \propto {\mu }^{\alpha }$. For the minimal ingredients of a gravitational field and a probe $U(1)$ gauge field in the bulk, we find general constraints $\alpha =1$ for the Maxwell action and $\alpha >1$ for the Born-Infeld case, for general background metrics. We show that the constraint $\alpha \ge 1$ can also be understood directly in the field theory from thermodynamic stability and causality. We then determine which values of $\alpha$ are realized in a large range of example systems, including $\mathrm{D}p\mathrm{\text{−}}\mathrm{D}q$ probe brane constructions and “bottom-up” models with gauge and scalar fields.

With the upgrade of current gravitational wave detectors, the first detection of gravitational wave signals is expected to occur in the next decade. Low-latency gravitational wave triggers will be necessary to make fast follow-up electromagnetic observations of events related to their source, e.g., prompt optical emission associated with short gamma-ray bursts. In this paper we present a new time-domain low-latency algorithm for identifying the presence of gravitational waves produced by compact binary coalescence events in noisy detector data. Our method calculates the signal to noise ratio from the summation of a bank of parallel infinite impulse response filters. We show that our summed parallel infinite impulse response method can retrieve the signal to noise ratio to greater than 99% of that produced from the optimal matched filter.

This paper presents a tunable effective-one-body (EOB) model for black-hole (BH) binaries of arbitrary mass ratio and aligned spins. This new EOB model incorporates recent results of small-mass-ratio simulations based on Teukolsky’s perturbative formalism. The free parameters of the model are calibrated to numerical-relativity simulations of nonspinning BH-BH systems of five different mass ratios and to equal-mass nonprecessing BH-BH systems with dimensionless BH spins ${\chi }_i\simeq \pm 0.44$. The present analysis focuses on the orbital dynamics of the resulting EOB model, and on the dominant $(\ell ,m)=(2,2)$ gravitational-wave mode. The calibrated EOB model can generate inspiral-merger-ringdown waveforms for nonprecessing, spinning BH binaries with any mass ratio and with individual BH spins $-1\le {\chi }_i\lesssim 0.7$. Extremizing only over time and phase shifts, the calibrated EOB model has overlaps larger than 0.997 with each of the seven numerical-relativity waveforms for total masses between $20M_{\odot }$ and $200M_{\odot }$, using the Advanced LIGO noise curve. We compare the calibrated EOB model with two additional equal-mass highly spinning (${\chi }_i\simeq -0.95,+0.97$) numerical-relativity waveforms, which were not used during calibration. We find that the calibrated model has an overlap larger than 0.995 with the simulation with nearly extremal antialigned spins. Extension of this model to black holes with aligned spins ${\chi }_i\gtrsim 0.7$ requires improvements of our modeling of the plunge dynamics and inclusion of higher-order PN spin terms in the gravitational-wave modes and radiation-reaction force.

Dark matter particle annihilation or decay can produce monochromatic gamma-ray lines and contribute to the diffuse gamma-ray background. Flux upper limits are presented for gamma-ray spectral lines from 7 to 200 GeV and for the diffuse gamma-ray background from 4.8 GeV to 264 GeV obtained from two years of Fermi Large Area Telescope data integrated over most of the sky. We give cross-section upper limits and decay lifetime lower limits for dark matter models that produce gamma-ray lines or contribute to the diffuse spectrum, including models proposed as explanations of the PAMELA and Fermi cosmic-ray data.

We study the ${\gamma }^{*}{\gamma }^{*}\to {\eta }_c$ transition form factor, $F_{{\eta }_c\gamma \gamma }(Q_1^2,Q_2^2)$, with the local-duality (LD) version of QCD sum rules. We analyze the extraction of this quantity from two different correlators, $⟨PVV⟩$ and $⟨AVV⟩$, with $P$, $A$, and $V$ being the pseudoscalar, axial-vector, and vector currents, respectively. The QCD factorization theorem for $F_{{\eta }_c\gamma \gamma }(Q_1^2,Q_2^2)$ allows us to fix the effective continuum thresholds for the $⟨PVV⟩$ and $⟨AVV⟩$ correlators at large values of $Q^2=Q_2^2$ and some fixed value of $\beta \equiv Q_1^2/Q_2^2$. We give arguments that, in the region $Q^2\ge 10–15{\mathrm{GeV}}^2$, the effective threshold should be close to its asymptotic value such that the LD sum rule provides reliable predictions for $F_{{\eta }_c\gamma \gamma }(Q_1^2,Q_2^2)$. We show that, for the experimentally relevant kinematics of one real and one virtual photon, the result of the LD sum rule for $F_{{\eta }_c\gamma }(Q^2)\equiv F_{{\eta }_c\gamma \gamma }(0,Q^2)$ may be well approximated by the simple monopole formula $F_{{\eta }_c\gamma }(Q^2)=2e_c^2{N}_c{f}_P(M_V^2+Q^2{)}^{-1}$, where $f_P$ is the ${\eta }_c$ decay constant, $e_c^2$ is the $c$-quark charge, and the parameter $M_V$ lies in the mass range of the lowest $\overline{c}c$ vector states.