We propose an approximation to the ground state of Yang-Mills theory, quantized in temporal gauge and $2+1$ dimensions, which satisfies the Yang-Mills Schrödinger equation in both the free-field limit, and in a strong-field zero mode limit. Our proposal contains a single parameter with dimensions of mass; confinement via dimensional reduction is obtained if this parameter is nonzero, and a nonzero value appears to be energetically preferred. A method for numerical simulation of this vacuum state is developed. It is shown that if the mass parameter is fixed from the known string tension in $2+1$ dimensions, the resulting mass gap deduced from the vacuum state agrees, to within a few percent, with known results for the mass gap obtained by standard lattice Monte Carlo methods.

Minimal walking technicolor models can provide a nontrivial solution for cosmological dark matter, if the lightest technibaryon is doubly charged. Technibaryon asymmetry generated in the early Universe is related to baryon asymmetry, and it is possible to create an excess of techniparticles with charge ($-2$). These excessive techniparticles are all captured by ${}^4\mathrm{He}$, creating techni-O-helium $t\mathrm{OHe}$ atoms, as soon as ${}^4\mathrm{He}$ is formed in big bang nucleosynthesis. The interaction of techni-O-helium with nuclei opens new paths to the creation of heavy nuclei in big bang nucleosynthesis. Because of the large mass of technibaryons, the $t\mathrm{OHe}$ “atomic” gas decouples from the baryonic matter and plays the role of dark matter in large scale structure formation, while structures in small scales are suppressed. Nuclear interactions with matter slow down cosmic techni-O-helium in the Earth below the threshold of underground dark matter detectors, thus escaping severe cryogenic dark matter search constraints. On the other hand, these nuclear interactions are not sufficiently strong to exclude this form of strongly interactive massive particles by constraints from the XQC experiment. Experimental tests of this hypothesis are possible in the search for $t\mathrm{OHe}$ in balloon-borne experiments (or on the ground) and for its charged techniparticle constituents in cosmic rays and accelerators. The $t\mathrm{OHe}$ atoms can cause cold nuclear transformations in matter and might form anomalous isotopes, offering possible ways to exclude (or prove?) their existence.

We study the scenario that conformal dynamics leads to metastable supersymmetry breaking vacua. At a high energy scale, the superpotential is not R-symmetric and has a supersymmetric minimum. However, conformal dynamics suppresses several operators along renormalization group flow toward the infrared fixed point. Then we can find an approximately R-symmetric superpotential, which has a metastable supersymmetry breaking vacuum, and the supersymmetric vacuum moves far away from the metastable supersymmetry breaking vacuum. We show a 4D simple model. Furthermore, we can construct 5D models with the same behavior, because of the AdS/CFT duality.

We investigate the production of gravitational waves due to quantum fluctuations of the vacuum during the transition from the inflationary to the radiation-dominated eras of the universe, assuming this transition to be dominated by the phenomenon of parametric resonance. The energy spectrum of the gravitational waves is calculated using the method of continuous Bogoliubov coefficients, which avoids the problem of overproduction of gravitons at large frequencies. We found, on the sole basis of the mechanism of quantum fluctuations, that the resonance field leaves no explicit and distinctive imprint on the gravitational-wave energy spectrum, apart from an overall upward or downward translation. Therefore, the main features in the spectrum are due to the inflaton field, which leaves a characteristic imprint at frequencies of the order of MHz/GHz.

The analysis of gravitational wave data may require greater accuracy than is afforded by the adiabatic approximation to the trajectory of and field produced by a particle moving in curved spacetime. Higher accuracy is available with a two-timescale approach using as an expansion parameter the ratio of orbital time to radiation reaction time. To avoid apparent divergences at large distances, the details of the method are important, especially the choice of the foliation, the spacetime surfaces on which the orbital elements are taken to be constant. Here we apply the two-timescale approach to a simple linear model to demonstrate the details of the method. In particular we use it to show that a null foliation avoids large-distance divergences in the first-order post-adiabatic approximation, and we argue that this will be true more generally for a null foliation.

I present a mechanism to transfer the spectrum of perturbations in a scalar isocurvature field $\xi$ onto the matter content in the radiation era via modulated, instant preheating after ekpyrosis. In this setup, $\xi$ determines the coupling constant relevant for the decay of a preheat matter field into fermions. The resulting power spectrum is scale invariant if $\xi$ remains close to a scaling solution in new ekpyrotic models of the Universe; by construction the spectrum is independent of the detailed physics near the bounce. The process differs from the curvaton mechanism, which has been used recently to revive the ekpyrotic scenario, in that no peculiar behavior of $\xi$ shortly before or during the bounce is needed. In addition, a concrete and efficient realization of reheating after ekpyrosis is provided; this mechanism is not tied to ekpyrotic models, but could equally well be used in other setups, for instance inflationary ones. I estimate non-Gaussianities and find no additional contributions in the most simple realizations, in contrast to models using the curvaton mechanism.

We study the dynamics of false vacuum bubbles. A nonminimally coupled scalar field gives rise to the effect of negative tension. The mass of a false vacuum bubble from an outside observer’s point of view can be positive, zero, or negative. The interior false vacuum has de Sitter geometry, while the exterior true vacuum background can have geometry depending on the vacuum energy. We show that there exist expanding false vacuum bubbles without the initial singularity in the past.

Some years ago it was shown that the cosmological constant may be reduced by thermal production of membranes that, after nucleation, collapse into a black hole. The probability of the process was calculated in the leading semiclassical approximation by studying an associated Euclidean configuration called the thermalon. Here we investigate the thermalon in three spacetime dimensions, describing the nucleation of closed strings that collapse into point particle singularities. In this context we may analyze the one-loop structure without the well-known problems brought in by the propagating gravitational degrees of freedom. We found that the coupling to gravity may increase the number of negative eigenvalues of the operator.

The topcolor-assisted technicolor (TC2) model predicts several pseudoscalars called top-pions and at loop level they can induce the flavor-changing neutral-current (FCNC) top-quark decay $t\to cgg$ which is extremely suppressed in the standard model (SM). We find that in the allowed parameter space the TC2 model can greatly enhance such a FCNC decay and push the branching ratio up to ${10}^{-3}$, which is much larger than the predictions in the SM (${10}^{-9}$) and in the minimal supersymmetric model (${10}^{-4}$). We also compare the result with the two-body FCNC decay $t\to cg$ and find that the branching ratio of $t\to cgg$ is at the same order as $t\to cg$. Such enhanced FCNC top-quark decays may serve as a good probe of the TC2 model at the future top-quark factory.

We derive the leptonic neutral current in the simplest little Higgs model and compute the contribution of the model to the decay width $Z\to e^{+}{e}^{-}$. Using the precision electroweak data we obtain a strong lower bound $f\ge 5.6\mathrm{TeV}$ at 95% C.L. on the characteristic energy scale of the model. It results in a lower bound for the new gauge bosons $W^{\prime \pm }$ and $Z^{\prime }$ as being $M_{W^{\prime \pm }}\ge 2.6\mathrm{TeV}$ and $M_{Z^{\prime }}\ge 3.1\mathrm{TeV}$, respectively. We also present the allowed values of the $k=f_1/f_2$ which is the parameter relating the two vacuum expectation values of the scalar triplets in the model, and the $\mu$ parameter of a quadratic term, involving the triplets, necessary to provide an acceptable mass range for the standard Higgs boson.

We consider two very different models of the flux tube linking two heavy quarks: a string linking the matter fields and a Coulombic description of two separately gauge invariant charges. We compare how close they are to the unknown true ground state in compact U(1) and the SU(2) Higgs model. Simulations in compact U(1) show that the string description is better in the confined phase but the Coulombic description is best in the deconfined phase; the last result is shown to agree with analytical calculations. Surprisingly in the nonabelian theory the Coulombic description is better in both the Higgs and confined phases. This indicates a significant difference in the width of the flux tubes in the two theories.

Recently, the Belle Collaboration has reported a resonant state produced in $B\to K\pi {\psi }^{\prime }$, which is called $Z(4430)$. This state is charged, so it can not be interpreted as an ordinary charmonium state. In this paper, we analyze the octet to which this particle belongs and predict the masses of mesons in this octet. Utilizing flavor SU(3) symmetry, we study production rates in several kinds of $B$ decays. The ${\overline{B}}^0\to Z_s^{-}{\pi }^{+}\to K^{-}{\psi }^{\prime }{\pi }^{+}$ and $B^{-}\to {\overline{Z}}_s^0{\pi }^{-}\to K_S{\psi }^{\prime }{\pi }^{-}$ decay channels, favored by Cabibbo-Kobayashi-Maskawa matrix elements, can have branching ratios of $\mathcal{O}({10}^{-5})$. This large branching ratio could be observed at the running $B$ factories to detect $Z_s$ particles containing a strange quark. We also predict large branching ratios of the $Z$ and $Z_c$ ($\overline{c}c\overline{c}D$, $D=u$, $d$, $s$) particle production rates in nonleptonic $B_c$ decays and radiative $B$ decays. Measurements of these decays at the ongoing $B$ factories and the forthcoming Large Hadron Collider-b experiments are helpful to clarify the mysterious $Z$ particles.

We consider ${\nu }_{\mu }\to {\nu }_{\tau }$ oscillations in the context of the mass varying neutrino (MaVaN) model, where the neutrino mass can vary depending on the electron density along the flight path of the neutrino. Our analysis assumes a mechanism with dependence only upon the electron density, hence ordinary matter density, of the medium through which the neutrino travels. Fully-contained, partially-contained and upward-going muon atmospheric neutrino data from the Super-Kamiokande detector, taken from the entire SK-I period of 1489 live days, are compared to MaVaN model predictions. We find that, for the case of 2-flavor oscillations, and for the specific models tested, oscillation independent of electron density is favored over density dependence. Assuming maximal mixing, the best-fit case and the density-independent case do not differ significantly.

The method of analytic continuation from imaginary to real chemical potentials $\mu$ is one of the few available techniques to study QCD at finite temperature and baryon density. One of its most appealing applications is the determination of the critical line for small $\mu$: we perform a direct test of the validity of the method in this case by studying two-color QCD, where the sign problem is absent. The (pseudo)critical line is found to be analytic around ${\mu }^2=0$, but a very large precision would be needed at imaginary $\mu$ to correctly predict the location of the critical line at real $\mu$.

In a previous paper, referred to as a “Mini-Landscape” search, we explored a “fertile patch” of the heterotic landscape based on a ${\mathbb{Z}}_6-\mathrm{II}$ orbifold with SO(10) and ${\mathrm{E}}_6$ local grand unified theory structures. In the present paper we extend this analysis. We find many models with the minimal supersymmetric standard model spectra and an exact $R$ parity. In all of these models, the vectorlike exotics decouple along $D$-flat directions. We present two benchmark models which satisfy many of the constraints of a realistic supersymmetric model, including nontrivial Yukawa matrices for three families of quarks and leptons and Majorana masses for right-handed neutrinos with nontrivial seesaw masses for the three light neutrinos. In an appendix we comment on the important issue of string selection rules and, in particular, the so-called “gamma-rule”.

In this paper we study the production of energetic dileptons. We calculate the rate for $2\to 2$ processes. The log term is obtained analytically and the constant term is calculated numerically. When the photon mass is of the order of the thermal quark mass, the result is insensitive to the photon mass and the soft logarithmic divergence is regulated by the thermal quark mass, exactly as in the case of real photons. We also consider the production of thermal Drell-Yan dileptons (thermal quark and antiquark pairs annihilating into virtual photons) and calculate the rate systematically in the context of the hard thermal loop effective theory. We obtain analytic and numerical results. We compare our results with those of previous calculations.

New techniques for the laboratory direct detection of dark matter weakly interacting massive particles (WIMPs) are sensitive to the recoil direction of the struck nuclei. We compute and compare the directional recoil rates $dR/d\cos \theta$ (where $\theta$ is the angle measured from a reference direction in the sky) for several WIMP velocity distributions including the standard dark halo and anisotropic models such as Sikivie’s late-infall halo model and logarithmic-ellipsoidal models. Since some detectors may be unable to distinguish the beginning of the recoil track from its end (lack of head-tail discrimination), we introduce a folded directional recoil rate $dR/d|\cos \theta |$, where $|\cos \theta |$ does not distinguish the head from the tail of the track. We compute the ${\mathrm{CS}}_2$ and ${\mathrm{CF}}_4$ exposures required to distinguish a signal from an isotropic background noise, and find that $dR/d|\cos \theta |$ is effective for the standard dark halo and some but not all anisotropic models.

Dark matter caustics are small scale, high density structures believed to exist in galaxies like ours. If the dark matter consists of weakly interacting massive particles, these caustics may be detected by means of the gamma rays produced by dark matter particle annihilation. We discuss particle annihilation in outer and inner caustics and provide sky maps of the expected gamma ray distribution.

A recently proposed idea of unparticles arising due to a scale invariant sector in the theory can give rise to effective operators with different Lorentz structures. We show that, by using the different polarization options at the future linear $e^{+}{e}^{-}$ colliders, the nature of these effective operators can be easily understood. The unique feature of a complex phase in the propagator of the unparticle can also be understood distinctively for the different spins by exploiting the initial beam polarizations at the International Linear Collider.

In this paper leading twist light cone wave functions of $2S$ state charmonium mesons are studied and models of these functions are built.