We discuss the prospects to measure galaxy-cluster properties via weak lensing of 21-cm fluctuations from the dark ages and the epoch of reionization (EOR). We choose as a figure of merit the smallest cluster mass detectable through such measurements. We construct the minimum-variance quadratic estimator for the cluster mass based on lensing of 21-cm fluctuations at multiple redshifts. We discuss the tradeoff among frequency bandwidth, angular resolution, and the number of redshift shells available for a fixed noise level for the radio detectors. Observations of lensing of the 21-cm background from the dark ages will be capable of detecting $M\gtrsim {10}^{12}{h}^{-1}{M}_{\odot }$ mass halos, but will require futuristic experiments to overcome the contaminating sources. Next-generation radio measurements of 21-cm fluctuations from the EOR will, however, have the sensitivity to detect galaxy clusters with halo masses $M\gtrsim {10}^{13}{h}^{-1}{M}_{\odot }$, given enough observation time (for the relevant sky patch) and collecting area to maximize their resolution capabilities.

Tensor modes in the cosmic microwave background are one of the most robust signatures of inflation. We derive theoretical bounds on the tensor fraction, as a generalization of the well-known Lyth bound. Under reasonable assumptions, the new bounds are at least 2 orders of magnitude stronger than the original one. We comment on a previously derived generalization, the so-called Efstathiou-Mack relationship. We also derive a new absolute upper bound on tensors using de Sitter entropy bounds.

The chiral partner structure of heavy baryons is studied using the bound state approach by binding the heavy-light mesons to the nucleon as the soliton in an effective Lagrangian for the pseudoscalar and vector mesons based on hidden local symmetry. In the heavy-light meson sector, we regard the $H$ doublet and $G$ doublet as chiral partners and couple them to light mesons with a minimal derivative. We find that the chiral partner of ${\Lambda }_c(\frac{1}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{+}}{},2286)$ is the ${\Lambda }_c(\frac{1}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{-}}{},\frac{3}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{-}}{})$ heavy quark doublet with a mass of about 3.1 GeV but not (${\Lambda }_c(\frac{1}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{-}}{},2595)$, ${\Lambda }_c(\frac{3}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{-}}{},2625)$), which might be interpreted as an orbital excitation of ${\Lambda }_c(\frac{1}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{+}}{},2286)$. The same model is applied to the bottom sector, and the chiral partner of ${\Lambda }_b(\frac{1}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{+}}{},5625)$ is shown to have a mass of about 6.5 GeV. We also discuss the chiral partner structures for the isospin vector heavy baryons. For the pentaquark states, we find that the masses of the pentaquark state made of a ground state heavy-light meson and its chiral partner are similar, and both of them are below the $Dp$ threshold, which therefore cannot be ruled out by the present data.

We study the impact of a leptophobic $Z^{\prime }$ gauge boson on the $C_{1q}$ and $C_{2q}$ parameters that describe the low-energy, parity-violating electron-quark neutral current interaction. We complement previous work by including the penguin-like vertex corrections, thereby completing the analysis of one-loop calculation up to $\mathcal{O}(m_{q^{\prime }}^2/M_{Z^{\prime }}^2)$ terms. We analyze the sensitivity of these probes to the different couplings $Z^{\prime }\overline{u}q$ ($q=u$, $c$, $t$) and $Z^{\prime }\overline{d}q$ ($q=d$, $s$, $b$) in a model-independent way that can be applied to any specific $Z^{\prime }$ scenario. We show that constraints from neutral kaon and heavy flavor studies preclude significant contributions from flavor nondiagonal couplings except for those involving top quarks. We apply our results to a light $Z^{\prime }$ with flavor diagonal couplings to up or down quarks, a scenario proposed in the literature to explain the CDF $W$ plus dijet anomaly. We find that such a particle would not affect the $C_{1q}$ coefficients, but it would have a sizable impact on $C_{2q}$ couplings that can be probed by future measurements of parity-violating deep inelastic scattering of polarized electrons off of deuterium.

We present results from our simulations of quantum chromodynamics with four flavors of quarks: $u$, $d$, $s$, and $c$. These simulations are performed with a one-loop Symanzik improved gauge action and the highly improved staggered quark action. We are generating gauge configurations with four values of the lattice spacing ranging from 0.06 to 0.15 fm, and three values of the light quark mass, including the value for which the Goldstone pion mass is equal to the physical pion mass. We discuss simulation algorithms, scale setting, taste symmetry breaking, and the autocorrelations of various quantities. We also present results for the topological susceptibility that demonstrate the improvement of the highly improved staggered quark configurations relative to those generated earlier with the asqtad improved staggered action.

We study single kaon production off the nucleon induced by electrons (positrons) i.e., $e^{-}(e^{+})+N\to {\nu }_e({\overline{\nu }}_e)+\overline{K}(K)+N^{\prime }$ at low energies. The possibility of observing these processes with the high luminosity beams available at TJNAF and Mainz is discussed, taking into account that the strangeness conserving electromagnetic reactions have a higher energy threshold for $\overline{K}$ ($K$) production. The calculations are done using a microscopic model that starts from the SU(3) chiral Lagrangians and includes background terms and the resonant mechanisms associated to the lowest lying resonance ${\Sigma }^{*}(1385)$.

We explore the possibility of light and superlight sterile neutrinos in the recently proposed minimal radiative inverse seesaw extension of the Standard Model for neutrino masses, in which all existing neutrino data can be explained. In particular, we discuss two benchmark scenarios with one of the three sterile neutrino states in the keV range, having very small mixing with the active neutrinos to account for the dark matter in the Universe, while (i) the other two light sterile neutrino states could be in the eV range, possessing a nonzero mixing with the active states as required to explain the $\mathrm{LSND}+\mathrm{MiniBooNE}+\mathrm{\text{reactor}}$ neutrino data, or (ii) one of the light sterile states is in the eV range, whereas the second one could be superlight and almost mass-degenerate with the solar neutrinos. Such superlight sterile neutrinos could give rise to potentially observable effects in future neutrino oscillation experiments and may also offer a possible explanation for the extra radiation observed in the Universe.

We investigate gravitational radiation in the linear approximation within the framework of the recent nonlocal generalization of Einstein’s theory of gravitation. In this theory, nonlocality can simulate dark matter; in fact, in the Newtonian regime, we recover the phenomenological Tohline-Kuhn approach to modified gravity. To account for the observational data regarding the rotation curves of spiral galaxies, nonlocality is associated with a characteristic length scale of order ${\lambda }_0=10\mathrm{kpc}$. It follows that in nonlocal gravity, the treatment of extremely low-frequency ($\sim {10}^{-12}\mathrm{Hz}$) gravitational waves with wavelengths of order ${\lambda }_0$ would be quite different than in general relativity. However, for radiation of frequency $\gtrsim {10}^{-8}\mathrm{Hz}$, which is the frequency range that is the focus of current observational searches, the corresponding wavelengths are very small compared to ${\lambda }_0$. We find that in this frequency regime the nonlocal deviations from general relativity essentially average out and can be safely neglected in practice.

We report on a comprehensive analysis of the renormalization of noncommutative ${\varphi }^4$ scalar field theories on the Groenewold-Moyal plane. These scalar field theories are twisted Poincaré invariant. Our main results are that these scalar field theories are renormalizable, free of UV/IR mixing, possess the same fixed points and $\beta$-functions for the couplings as their commutative counterparts. We also argue that similar results hold true for any generic noncommutative field theory with polynomial interactions and involving only pure matter fields. A secondary aim of this work is to provide a comprehensive review of different approaches for the computation of the noncommutative $S$-matrix: noncommutative interaction picture and noncommutative Lehmann-Symanzik-Zimmermann formalism.

Ideas from causal set theory lead to a fluctuating, time-dependent cosmological constant of the right order of magnitude to match currently quoted “dark energy” values. Although this effect was predicted some time ago [R. D. Sorkin, in Relativity and Gravitation: Classical and Quantum, Proceedings of the SILARG VII Conference, Cocoyoc, Mexico, 1990, edited by J. C. D’Olivo, E. Nahmad-Achar, M. Rosenbaum, M. P. Ryan, L. F. Urrutia, and F. Zertuche (World Scientific, Singapore, 1991), pp. 150–173; Rafael D. Sorkin, Int. J. Theor. Phys. 36, 2759 (1997).], it is only more recently that a more detailed phenomenological model of a fluctuating $\Lambda$ was introduced and simulated numerically [M. Ahmed, S. Dodelson, P. Greene, and R. D. Sorkin, Phys. Rev. D 69, 103523 (2004).]. In this paper we continue the investigation by studying the sensitivity of the model to some of the ad hoc choices made in setting it up.

We propose a curvaton model in which the initial condition of the curvaton oscillation is determined by its attractor behavior during inflation. Assuming a chaotic inflation model, we find that the initial condition determined by the attractor behavior is appropriate to generate a sizable non-Gaussianity contribution to the curvature perturbation, which will be tested in the foreseeable future. Implications on the thermal history of the Universe and on particle physics models are also discussed.

Massive gravity is a modified theory of general relativity. In this paper, we study, using a method in which the scale factor changes as a particle in a “potential,” all possible cosmic evolutions in a ghost-free massive gravity. We find that there exists, in certain circumstances, an oscillating universe or a bouncing one. If the universe starts at the oscillating region, it may undergo a number of oscillations before it quantum mechanically tunnels to the bounce point and then expands forever. But going back to the singularity from the oscillating region is physically not allowed. So, the big bang singularity can be successfully resolved. At the same time, we also find that there exists a stable Einstein static state in some cases. However, the universe cannot stay at this stable state past eternally since it is allowed to quantum mechanically tunnel to a big-bang-to-big-crunch region and end with a big crunch. Thus, a stable Einstein static state universe cannot be used to avoid the big bang singularity in massive gravity.

We consider a massive quantum test Klein-Gordon field probing a homogeneous isotropic quantum cosmological space-time in the background. In particular, we derive a semiclassical space-time which emerges to a mode of the field. The method consists of a comparison between quantum field theory on a quantum background and quantum field theory on a classical curved space-time, giving rise to an emergent metric tensor (its components being computed from the equation of propagation of the quantum Klein-Gordon field in the test field approximation). If the field is massless the emergent metric is of the Friedmann-Robertson-Walker form, but if a mass term is considered it turns out that the simplest emergent metric that displays the symmetries of the system is of the Bianchi I type, deformed in the direction of propagation of the particle. This anisotropy is of a quantum nature: it is proportional to $\hslash$ and “dresses” the isotropic classical space-time obtained in the classical limit.

Baryon interactions with bosonic dark matter are constrained by the potential for dark-matter-rich neutron stars to collapse into black holes. We consider the effect of dark matter self-interactions and dark matter annihilation on these bounds, and treat the evolution of the black hole after formation. We show that, for nonannihilating dark matter, these bounds extend up to $m_X\sim {10}^{5–7}\mathrm{GeV}$, depending on the strength of self-interactions. However, these bounds are completely unconstraining for annihilating bosonic dark matter with an annihilation cross section of $⟨{\sigma }_{a}v⟩\gtrsim {10}^{-38}{\mathrm{cm}}^3/\mathrm{s}$. Dark matter decay does not significantly affect these bounds. We thus show that bosonic dark matter accessible to near-future direct detection experiments must participate in an annihilation or self-interaction process to avoid black hole collapse constraints from very old neutron stars.

We study an extension of the minimal supersymmetric Standard Model with a gauge group $SU(2{)}_1\otimes SU(2{)}_2$ breaking to $SU(2{)}_L$. The extra wino has an enhanced gauge coupling to the Standard Model-like Higgs boson and, if light, has a relevant impact on the weak-scale phenomenology. The low-energy Higgs quartic coupling is modified by both extra $D$-term corrections and a modification of its renormalization group evolution from high energies. At low values of $\tan \beta$, the latter effect may be dominant. This leads to interesting regions of parameter space in which the model can accommodate a 125 GeV Higgs with relatively light third-generation squarks and an increased $h\to \gamma \gamma$ decay branching ratio, while still satisfying the constraints from electroweak precision data and Higgs vacuum stability.

The spherical vortex as introduced in [G. Jordan et al., Phys. Rev. D 77, 014515 (2008)] is generalized. A continuum form of the spherical vortex is derived and investigated in detail. The discrepancy between the gluonic lattice topological charge and the index of the lattice Dirac operator described in previous papers is identified as a discretization effect. The importance of the investigations for Monte Carlo configurations is discussed.

We derive a nonequilibrium fluctuation-dissipation relation for bosonic correlation functions from holography in the classical gravity approximation at strong coupling. This generalizes the familiar thermal fluctuation-dissipation relation in the absence of external sources. This also holds universally for any nonequilibrium state which can be obtained from a stable thermal equilibrium state in perturbative derivative (hydrodynamic) and amplitude (nonhydrodynamic) expansions. Therefore, this can provide a strong experimental test for the applicability of the holographic framework. We discuss how it can be tested in heavy-ion collisions. We also make a conjecture regarding multipoint holographic nonequilibrium Green’s functions.

In the framework of the semiclassical approach, we find the leading finite-size effects on the normalized structure constants in some three-point correlation functions in $Ad{S}_5\times S^5$, expressed in terms of the conserved string angular momenta $J_1$, $J_2$, and the world-sheet momentum $p_w$, identified with the momentum $p$ of the magnon excitations in the dual spin chain arising in $\mathcal{N}=4$ super Yang-Mills theory in four dimensions.