Composite dark matter candidates, which can arise from new strongly-coupled sectors, are well-motivated and phenomenologically interesting, particularly in the context of asymmetric generation of the relic density. In this work, we employ lattice calculations to study the electromagnetic form factors of electroweak-neutral dark-matter baryons for a three-color, QCD-like theory with $N_f=2$ and 6 degenerate fermions in the fundamental representation. We calculate the (connected) charge radius and anomalous magnetic moment, both of which can play a significant role for direct detection of composite dark matter. We find minimal $N_f$ dependence in these quantities. We generate mass-dependent cross sections for dark matter-nucleon interactions and use them in conjunction with experimental results from XENON100, excluding dark matter candidates of this type with masses below 10 TeV.

The lowest-order hadronic contribution to the $g\mathrm{\text{−}}2$ factor of the muon is analyzed in the framework of the operator product expansion at short distances, and a QCD finite energy sum rule designed to quench the role of the $e^{+}{e}^{-}$ data. This procedure reduces the discrepancy between experiment and theory, $\Delta a_{\mu }\equiv a_{\mu }^{\mathrm{EXP}}-a_{\mu }^{\mathrm{SM}}$, from $\Delta a_{\mu }=28.7(8.0)\times {10}^{-10}$ to $\Delta a_{\mu }=19.2(8.0)\times {10}^{-10}$, i.e. without changing the uncertainty.

Recent experimental results from RHIC and LHC on hard photon emission rates in heavy-ion collisions indicate a large azimuthal asymmetry of photon emission rate parametrized by the elliptic flow $v_2$. Motivated by a recent proposal that the early magnetic field created by two colliding heavy ions may be responsible for this large azimuthal asymmetry of photon emission rate, we compute the azimuthal dependence of the photon emission rate from a strongly coupled finite temperature plasma with magnetic field in the framework of gauge/gravity correspondence. We also propose and compute a new observable, “in/out-plane polarization asymmetry,” constructed from the polarization dependence of the photon emission rates. We observe that both the azimuthal and polarization asymmetry of photon emissions are strongly affected by the triangle anomaly (chiral anomaly) for the low frequency regime below 1 GeV.

We explore the phenomenological viability of a light $Z^{\prime }$ in heterotic-string models, whose existence has been motivated by proton stability arguments. A class of quasirealistic string models that produce such a viable $Z^{\prime }$ are the left-right symmetric (LRS) heterotic-string models in the free fermionic formulation. A key feature of these models is that the matter charges under $U(1{)}_{Z^{\prime }}$ do not admit an $E_6$ embedding. The light $Z^{\prime }$ in the LRS heterotic-string models forbids baryon number violating operators, while allowing lepton number violating operators, hence suppressing proton decay yet allowing for sufficiently small neutrino masses via a seesaw mechanism. We show that the constraints imposed by the gauge coupling data and heterotic-string coupling unification nullify the viability of a light $Z^{\prime }$ in these models. We further argue that agreement with the gauge coupling data necessitates that the $U(1{)}_{Z^{\prime }}$ charges admit an $E_6$ embedding. We discuss how viable string models with this property may be constructed.

Considering quantum gravity within the framework of effective field theory, we investigated the consequences of spontaneous Lorentz violation for the gravitational potential. In particular, we focus our attention on the bumblebee models, in which the graviton couples to a vector $B_{\mu }$ that assumes a nonzero vacuum expectation value. The leading order corrections for the nonrelativistic potential are obtained from calculation of the scattering matrix of two scalar particles interacting gravitationally. These corrections imply anisotropic properties associated with the bumblebee background and also add a Darwin-like term for Newton’s potential.

The transition probabilities for a single neutrino emitted from a point proto-neutron source after passage through a turbulent supernova density profile have been found to be random variates drawn from parent distributions whose properties depend upon the stage of the explosion, the neutrino energy and mixing parameters, the observed channel, and the properties of the turbulence such as the amplitude $C_{\star }$. In this paper we examine the consequences of the recently measured mixing angle ${\theta }_{13}$ upon the neutrino flavor transformation in supernova when passing through turbulence, in order to provide some clarity as to what one should expect in the way of turbulence effects in the next supernova neutrino burst signal. We find that the measurements of a relatively large value of ${\theta }_{13}$ means the neutrinos are relatively immune to small, $C_{\star }\lesssim 1\%$, amplitude turbulence but as $C_{\star }$ increases the turbulence effects grow rapidly and spread to all mixing channels. For $C_{\star }\gtrsim 10\%$ the turbulence effects in the high density resonance mixing channels are independent of ${\theta }_{13}$ but nonresonant mixing channels are more sensitive to turbulence when ${\theta }_{13}$ is large.

We begin the study of a class of string-motivated effective supergravity theories in light of current data from the CERN Large Hadron Collider (LHC). The case of heterotic string theory, in which the dilaton is stabilized via nonperturbative corrections to the Kähler metric, will be considered first. The model, which represents the strong dynamics of a presumed gaugino condensation in the hidden sector, is highly constrained and therefore predictive. We find that much of the parameter space associated with confined hidden sector gauge groups up to rank five is now observationally disfavored by the LHC results. Most of the theoretically motivated parameter space that remains can be probed with data that has already been collected, and most of the remainder will be definitively explored within the first year of operation at $\sqrt{s}=13\mathrm{TeV}$. Expected signatures for a number of benchmark points are discussed. We find that the surviving space of the model makes a precise prediction as to the relation of many superpartner masses, as well as the manner in which the correct dark matter relic density is obtained. Implications for current and future dark matter search experiments are discussed.

When four scalar fields with global Lorentz symmetry are coupled to gravity and take a vacuum expectation value, breaking diffeomorphism invariance spontaneously, the graviton becomes massive. This model is supersymmetrized by considering four $N=1$ chiral superfields with global Lorentz symmetry. The global supersymmetry is promoted to a local one using the rules of tensor calculus of coupling the $N=1$ supergravity Lagrangian to the four chiral multiplets. When the scalar components of the chiral multiplets $z^A$ acquire a vacuum expectation value, both diffeomorphism invariance and local supersymmetry are broken spontaneously. The global Lorentz index $A$ becomes identified with the space-time Lorentz index, making the scalar fields $z^A$ vectors and the chiral spinors ${\psi }^A$ spin-$3/2$ Rarita-Schwinger fields. We show that the spectrum of the model in the broken phase consists of a massive spin-2 field, two massive spin-$3/2$ fields with different mass and a massive vector.

In a quantum system, there may be many density matrices associated with a state on an algebra of observables. For each density matrix, one can compute its entropy. These are, in general, different. Therefore, one reaches the remarkable possibility that there may be many entropies for a given state [R. Sorkin (private communication)]. This ambiguity in entropy can often be traced to a gauge symmetry emergent from the nontrivial topological character of the configuration space of the underlying system. It can also happen in finite-dimensional matrix models. In the present work, we discuss this entropy ambiguity and its consequences for an ethylene molecule. This is a very simple and well-known system, where these notions can be put to tests. Of particular interest in this discussion is the fact that the change of the density matrix with the corresponding entropy increase drives the system towards the maximally disordered state with maximum entropy, where Boltzman’s formula applies. Besides its intrinsic conceptual interest, the simplicity of this model can serve as an introduction to a similar discussion of systems such as colored monopoles and the breaking of color symmetry.

We consider the importance of the second-order dissipative self-force for gravitational wave dephasing for an extreme or intermediate mass ratio system moving along a quasicircular Schwarzschild orbit. For the first-order self-force we use the fully relativistic force in the Lorenz gauge for eternally circular geodesics. The second-order self-force is modeled by its 3.5 post-Newtonian counterpart. We evolve the system using the osculating orbits method, and obtain the gravitational waveforms, whose phase includes all the terms—within our approximation (and using the self-force along circular geodesics)—that are independent of the system’s mass ratio. The partial dephasing due to the second-order dissipative self-force is substantially smaller than that of the first-order conservative self-force, although they are both at the same order in the mass ratio.

We perform several black-hole binary evolutions using fully nonlinear numerical relativity techniques at separations large enough that low-order post-Newtonian expansions are expected to be accurate. As a case study, we evolve an equal-mass nonspinning black-hole binary from a quasicircular orbit at an initial coordinate separation of $D=100M$ for three different resolutions. We find that the orbital period of this binary (in the numerical coordinates) is $T=6422M$. The orbital motion agrees with post-Newtonian predictions to within 1%. However, we find that the time derivative of the coordinate separation is dominated by a purely gauge effect leading to an apparent contraction and expansion of the orbit at twice the orbital frequency. Based on these results, we improved our evolution techniques and studied a set of black hole binaries in quasicircular orbits starting at $D=20M$, $D=50M$, and $D=100M$ for $\sim 5$, 3, and 2 orbits, respectively. We then find good agreement between the numerical results and post-Newtonian predictions for the orbital frequency and radial decay rate, radiated energy and angular momentum, and waveform amplitude and phases. The results are relevant for the future computation of long-term waveforms to assist in the detection and analysis of gravitational waves by the next generation of detectors as well as the long-term simulations of black-hole binaries required to accurately model astrophysically realistic circumbinary accretion disks.

Recently, a new holographic dark energy (HDE) model with action principle was proposed [M. Li and R. X. Miao, arXiv:1210.0966]. It is the first time that the HDE model is derived from the action principle. This model completely solves the causality and circular problems in the original HDE model and automatically gives rise to a dark radiation component. Thus, it is worth investigating such an interesting model by confronting it with the current cosmological observations, so that we can check whether the model is consistent with the data and determine the regions of parameter space allowed. These issues are explored in this work. First, we investigate the dynamical behaviors and the cosmic expansion history of the model and discuss how they are related with the model parameter $c$. Then, we fit the model to a combination of the present $\mathrm{\text{Union}}2.1+\mathrm{BAO}+\mathrm{CMB}+H_0$ data. We find the model yields ${\chi }_{\min }^2=548.798$ (in a nonflat universe), comparable to the results of the original HDE model (549.461) and the concordant $\Lambda \mathrm{CDM}$ model (550.354). At 95.4% C.L., we get $1.41<c<3.09$ and correspondingly $-2.25<w(z=-1)<-1.39$, implying the big-rip fate of the Universe at a high confidence level. Besides, for the constraints on dark radiation, we also get a rough estimation $N_{\mathrm{eff}}={3.54}_{-0.45-0.76}^{+0.32+0.67}$, with the central value slightly larger than the standard value 3.046.

We perform an all-sky analysis of the general relativistic galaxy power spectrum using the well-developed spherical Fourier decomposition. Spherical Fourier analysis expresses the observed galaxy fluctuation in terms of the spherical harmonics and spherical Bessel functions that are angular and radial eigenfunctions of the Helmholtz equation, providing a natural orthogonal basis for all-sky analysis of the large-scale mode measurements. Accounting for all the relativistic effects in galaxy clustering, we compute the spherical power spectrum and its covariance matrix and compare it to the standard three-dimensional power spectrum to establish a connection. The spherical power spectrum recovers the three-dimensional power spectrum at each wave number $k$ with its angular dependence ${\mu }_k$ encoded in angular multipole $l$, and the contributions of the line-of-sight projection to galaxy clustering such as the gravitational lensing effect can be readily accommodated in the spherical Fourier analysis. A complete list of formulas for computing the relativistic spherical galaxy power spectrum is also presented.

The Atacama Cosmology Telescope (ACT) and the South Pole Telescope (SPT) have recently provided new, very precise measurements of the cosmic microwave background (CMB) anisotropy damping tail. The values of the cosmological parameters inferred from these measurements, while broadly consistent with the expectations of the standard cosmological model, are providing interesting possible indications for new physics that are definitely worthy of investigation. The ACT results, while compatible with the standard expectation of three-neutrino families, indicate a level of CMB lensing, parametrized by the lensing amplitude parameter $A_L$, that is about 70% higher than expected. If not caused by an experimental systematic, an anomalous lensing amplitude could be produced by modifications of general relativity or coupled dark energy. Vice versa, the SPT experiment, while compatible with a standard level of CMB lensing, prefers an excess of dark radiation, parametrized by the effective number of relativistic degrees of freedom $N_{\mathrm{eff}}$. Here we perform a new analysis of these experiments allowing simultaneous variations in both of these nonstandard parameters. We also combine these experiments, for the first time in the literature, with the recent WMAP9 data, one at a time. Including the Hubble Space Telescope prior on the Hubble constant and information from baryon acoustic oscillations surveys provides the following constraints from ACT: $N_{\mathrm{eff}}=3.54\pm 0.41$, $A_L=1.64\pm 0.32$ at 68% C.L., while for SPT we have $N_{\mathrm{eff}}=3.78\pm 0.33$, $A_L=0.79\pm 0.11$ at 68% C.L. In particular, the $A_L$ estimates from the two experiments, even when a variation in $N_{\mathrm{eff}}$ is allowed, are in tension at more than 95% C.L.

The role of hadronic matter in the suppression of open heavy-flavored mesons is studied. The heavy-quark suppression factors are calculated and contrasted with the experimental data obtained from nuclear collisions at the Relativistic Heavy Ion Collider (RHIC) and LHC experiments. It is found that the suppression in the hadronic phase at RHIC energy is around 20%–25% whereas at the LHC it is around 10%–12% for the $D$ meson. In the case of $B$ mesons the hadronic suppression is around 10%–12% and 5%–6% at RHIC and LHC energies, respectively. The present study suggests that the suppression of heavy flavor in the hadronic phase is significant at the RHIC. However, the effect of hadronic suppression at the LHC is marginal; this makes the characterization of quark-gluon plasma at the LHC less complicated.

We suggest a minimal extension of the simplest $A_4$ flavor model that can induce a nonzero ${\theta }_{13}$ value, as required by recent neutrino oscillation data from reactors and accelerators. The predicted correlation between the atmospheric mixing angle ${\theta }_{23}$ and the magnitude of ${\theta }_{13}$ leads to an allowed region substantially smaller than indicated by neutrino-oscillation global fits. Moreover, the scheme correlates $CP$ violation in neutrino oscillations with the octant of the atmospheric mixing parameter ${\theta }_{23}$ in such a way that, for example, maximal mixing necessarily violates $CP$. We briefly comment on other phenomenological features of the model.

We investigate differences and similarities between fundamental fermions and adjoint fermions in $SU(N)$ gauge theory. The gauge theory with fundamental fermions possesses ${\mathbb{Z}}_N$ symmetry only in the limit of infinite fermion mass, whereas the gauge theory with adjoint fermions does have the symmetry for any fermion mass. The flavor-dependent twisted boundary condition (FTBC) is then imposed on fundamental fermions so that the theory with fundamental fermions can possess ${\mathbb{Z}}_N$ symmetry for any fermion mass. We show similarities between FTBC fundamental fermions and adjoint fermions, using the Polyakov-loop extended Nambu–Jona-Lasinio (PNJL) model. In the mean-field level, the PNJL model with FTBC fundamental fermions has dynamics similar to the PNJL model with adjoint fermions for the confinement-deconfinement transition related to ${\mathbb{Z}}_N$ symmetry. The chiral property is somewhat different between the two models, but there is a simple relation between chiral condensates in the two models. As an interesting high-energy phenomenon, a possibility of the gauge symmetry breaking is studied for FTBC fundamental fermions.

We introduce a four-dimensional cutoff in the scenario of gauge-Higgs unification to control the ultraviolet behavior. A one-loop effective potential for a Higgs field and the Higgs mass are obtained with the cutoff. We find an interrelation between the four-dimensional cutoff and the scale of extra dimensions, which is concretized through the Higgs mass. Combining this interrelation and the recently discovered Higgs boson at the LHC, we obtain an interesting constraint for the four-dimensional cutoff and the extra-dimensional scale.

We study a composite millicharged dark matter model. The dark matter is in the form of pionlike objects emerging from a higher scale QCD-like theory. We present two distinct possibilities with interesting phenomenological consequences based on the choice of the parameters. In the first one, the dark matter is produced nonthermally, and it could potentially account for the 130 GeV Fermi photon line via decays of the “dark pions.” We estimate the self-interaction cross section, which might play an important role both in changing the dark matter halo profile at the center of the galaxy and in making the dark matter warmer. In the second version the dark matter is produced via the freeze-in mechanism. Finally we impose all possible astrophysical, cosmological and experimental constraints. We study in detail generic constraints on millicharged dark matter that can arise from anomalous isotope searches of different elements and we show why constraints based on direct searches from underground detectors are not generally valid.

Based on the Hamiltonian formalism approach, a generalized Lüscher’s formula for two-particle scattering in both the elastic and coupled-channel cases in moving frames is derived from a relativistic Lippmann-Schwinger equation. Some strategies for extracting scattering amplitudes for a coupled-channel system from the discrete finite-volume spectrum are discussed and illustrated with a toy model of two-channel resonant scattering. This formalism will, in the near future, be used to extract information about hadron scattering from lattice quantum chromodynamics computations.