A systematic search for Lie-algebra solutions of the type IIB matrix model is performed. Our survey is based on the classification of all Lie algebras for dimensions up to five and of all nilpotent Lie algebras of dimension six. It is shown that Lie-type solutions of the equations of motion of the type IIB matrix model exist and they correspond to certain nilpotent and solvable Lie algebras. Their representation in terms of Hermitian matrices is discussed in detail. These algebras give rise to certain noncommutative spaces for which the corresponding star products are provided. Finally the issue of constructing quantized compact nilmanifolds and solvmanifolds based on the above algebras is addressed.

Irreversibility and acausality of a subsystem are established in exactly soluble harmonic models with reversible and causal dynamics. It is shown that initial conditions, imposed on some dynamical degrees of freedom may break time reversal invariance for other degrees of freedom. This happens if observations carried out in any large but finite amount of time can not resolve the spectrum of the eliminated degrees of freedom, namely, when the spectrum has a condensation point at the ground state. Acausality follows due to the dominance of the dynamics by almost time-independent modes.

Collisional processes in ultrarelativistic $\mathcal{N}=1$ supersymmetric QED plasma are studied and compared to those in an electromagnetic plasma of electrons, positrons and photons. Cross sections of all binary interactions which occur in the supersymmetric plasma at the order of $e^4$ are computed. Some processes, in particular, the Compton scattering on selectrons, appear to be independent of momentum transfer and thus they are qualitatively different from processes in an electromagnetic plasma. It suggests that the transport properties of the supersymmetric plasma are different than those of its nonsupersymmetric counterpart. Energy loss and momentum broadening of a particle traversing the supersymmetric plasma are discussed in detail and the characteristics are shown to be surprisingly similar to those of QED plasma.

In this paper the generalization of the Gribov pendulum equation in the Coulomb gauge for curved space-times is analyzed on static spherically symmetric backgrounds. A rigorous argument for the existence and uniqueness of solution is provided in the asymptotically AdS case. The analysis of the strong and weak boundary conditions is equivalent to analyzing an effective one-dimensional Schrödinger equation. Necessary conditions in order for spherically symmetric backgrounds to admit solutions of the Gribov pendulum equation representing copies of the vacuum satisfying the strong boundary conditions are given. It is shown that asymptotically flat backgrounds do not support solutions of the Gribov pendulum equation of this type, while on asymptotically AdS backgrounds such ambiguities can appear. Some physical consequences are discussed.

Using the Pais-Uhlenbeck oscillator as a toy model, we outline a consistent alternative to the indefinite-metric quantization scheme that does not violate unitarity. We describe the basic mathematical structure of this method by giving an explicit construction of the Hilbert space of state vectors and the corresponding creation and annihilation operators. The latter satisfy the usual bosonic commutation relation and differ from those of the indefinite-metric theories by a sign in the definition of the creation operator. This change of sign achieves a definitization of the indefinite metric that gives life to the ghost states without changing their contribution to the energy spectrum.

The mutual and tripartite information between pairs and triples of disjoint regions in a quantum field theory are sensitive probes of the spread of correlations in an equilibrating system. We compute these quantities in strongly coupled two-dimensional conformal field theories with a gravity dual following the homogenous deposition of energy. The injected energy is modeled in anti-de Sitter space as an infalling shell, and the information shared by disjoint intervals is computed in terms of geodesic lengths in this background. For given widths and separation of the intervals, the mutual information typically starts at its vacuum value, then increases in time to reach a maximum, and then declines to the value at thermal equilibrium. A simple causality argument qualitatively explains this behavior. The tripartite information is generically nonzero and time-dependent throughout the process. This contrasts with (but does not contradict) the time-independent tripartite information one finds after a two-dimensional quantum quench in the limit of large time and distance scales compared to the initial inverse mass gap.

We discuss the expansions used in spin foam cosmology. We point out that already at the one-vertex level, arbitrarily complicated amplitudes contribute and discuss the geometric asymptotics of the five simplest ones. We discuss what type of consistency conditions would be required to control the expansion. We show that the factorization of the amplitude originally considered is best interpreted in topological terms. We then consider the next-higher term in the graph expansion. We demonstrate the tension between the truncation to small graphs and going to the homogeneous sector and conclude that it is necessary to truncate the dynamics as well.

Weak lensing surveys exploit measurements of galaxy ellipticities. These measurements are subject to errors, which degrade the cosmological information that can be extracted from the surveys. Here, we propose a way of using the galaxy data themselves to calibrate the measurement errors. In particular, the cosmic shear field, which causes the galaxies to appear elliptical, also changes their sizes and fluxes. Information about the sizes and fluxes of the galaxies can be added to the shape information to obtain more robust information about the cosmic shear field. The net result will be tighter constraints on cosmological parameters such as those which describe dark energy.

We consider a simple model of cosmological collapse driven by canonical fields with exponential potentials. We generalize the two-field ekpyrotic collapse to consider nonorthogonal or tilted potentials and give the general condition for isocurvature field fluctuations to have a scale-invariant spectrum in this model. In particular we show that tilted potentials allow for a slightly red spectrum of perturbations as required by current observations. However a red spectrum of fluctuations implies that the two-field ekpyrotic phase must have a finite duration and requires a preceding phase which sets the initial conditions for what otherwise appears to be a fine-tuned trajectory in the phase space.

We study energy transport by asymmetric dark matter (ADM) in very low-mass stars and brown dwarfs. Our motivation is to explore astrophysical signatures of ADM, which may not otherwise be amenable to indirect dark matter searches. In viable models, the additional cooling of low-mass stellar cores can alter stellar properties. ADM with mass $4\lesssim M_{\mathrm{x}}/\mathrm{GeV}\lesssim 10$ and a spin-dependent (spin-independent) cross section of ${\sigma }_{\mathrm{p}}^{\mathrm{SD}}\sim {10}^{-37}{\mathrm{cm}}^2$ (${\sigma }_{\mathrm{p}}^{\mathrm{SI}}\sim {10}^{-40}{\mathrm{cm}}^2$) increases the minimum mass of main sequence hydrogen burning, partly determining whether or not the object is a star at all. Similar ADM candidates reduce the luminosities of low-mass stars and accelerate the cooling of brown dwarfs. Such light dark matter is of interest given results from the DAMA and CoGeNT dark matter searches. We discuss possibilities for observing dark matter effects in stars and exploiting these effects to constrain dark matter candidates.

We analyze the sector of dimension-three vector meson operators in the “hard-wall” model of holographic QCD, including the vector and axial currents, dual to gauge fields in the bulk, and the tensor operator $\overline{\psi }{\sigma }^{\mu \nu }\psi$, dual to a two-form field satisfying a complex self-duality condition. The model includes the effect of chiral symmetry breaking on vector mesons, that involves a coupling between the dual gauge field and the two-form field. We compute the leading logarithmic terms in the operator product expansion of two-point functions and the leading nonperturbative contribution to the tensor-vector correlator. The result is consistent with the operator product expansion of QCD. We also study the spectrum of vector mesons numerically.

The simplest non-Abelian gauge extension of the electroweak standard model, the $SU(3{)}_c\otimes SU(3{)}_L\otimes U(1{)}_N$, known as the 3-3-1 model, has a minimal version which demands the least possible fermionic content to account for the whole established phenomenology for the well-known particles and interactions. Nevertheless, in its original form the minimal 3-3-1 model was proposed with a set of three scalar triplets and one sextet in order to yield the spontaneous breaking of the gauge symmetry and generate the observed fermion masses. Such a huge scalar sector turns the task of clearly identifying the physical scalar spectrum into a clumsy labor. It not only adds an obstacle for the development of its phenomenology, but implies a scalar potential plagued with new free coupling constants. In this work, we show that the framework of the minimal 3-3-1 model can be built with only two scalar triplets, but still triggering the desired pattern of spontaneous symmetry breaking and generating the correct fermion masses. We present the exact physical spectrum and also show all the interactions involving the scalars, obtaining a neat minimal 3-3-1 model far more suited for phenomenological studies at the current Large Hadron Collider.

We examine the low scale particle spectroscopy of an SO(10) [or equivalently SU(5)] inspired supersymmetric model with nonuniversal gaugino masses. The model assumes minimal supergravity and contains the same number of fundamental parameters as the constrained minimal supersymmetric standard model. Realistic solutions compatible with dark matter and other applicable experimental constraints are shown to exist for both positive and negative signs of the minimal supersymmetric standard model parameter $\mu$. We present several benchmark points which will be tested at the LHC and by the ongoing direct and indirect dark matter detection experiments.

We propose a method to evaluate spectral functions on the lattice based on a variational method. On a lattice with a finite spatial extent, spectral functions consist of discrete spectra only. Adopting a variational method, we calculate the locations and the heights of spectral functions at low-lying discrete spectra. We first test the method in the case of analytically solvable free Wilson quarks at zero and finite temperatures and confirm that the method well reproduces the analytic results for low-lying spectra. We find that we can systematically improve the results by increasing the number of trial states. We then apply the method to calculate the charmonium spectral functions for $S$ and $P$-wave states at zero-temperature in quenched QCD and compare the results with those obtained using the conventional maximum entropy method (MEM). The results for the ground state are consistent with the location and the area of the first peak in spectral functions from the MEM, while the variational method leads to a mass which is closer to the experimental value for the first excited state. We also investigate the temperature dependence of the spectral functions for $S$-wave states below and above $T_c$. We obtain no clear evidences for dissociation of $J/\psi$ and ${\eta }_c$ up to $1.4T_c$.

We study numerically the SU(2) Landau gauge transverse and longitudinal gluon propagators at nonzero temperatures $T$ both in confinement and deconfinement phases. Special attention is paid to the Gribov copy effects in the IR region. Applying a powerful gauge fixing algorithm, we find that the Gribov copy effects for the transverse propagator $D_T(p)$ are very strong in the infrared, while the longitudinal propagator $D_L(p)$ shows very weak (if any) Gribov copy dependence. The value $D_T(0)$ tends to decrease with growing lattice size; however, $D_T(0)$ is nonzero in the infinite volume limit, in disagreement with the suggestion made in [I. Zahed and D. Zwanziger, Phys. Rev. D 61, 037501 (2000).]. We show that in the infrared region, $D_T(p)$ is not consistent with the pole-type formula not only in the deconfinement phase but also for $T<T_c$. We introduce a new definition of the magnetic infrared mass scale (“magnetic screening mass”) $m_M$. The electric mass $m_E$ has been determined from the momentum space longitudinal gluon propagator. We study also the (finite) volume and temperature dependence of the propagators as well as discretization errors.

We combine the six-dimensional helicity formalism of Cheung and O’Connell with $D$-dimensional generalized unitarity to obtain a new formalism for computing one-loop amplitudes in dimensionally regularized QCD. With this procedure, we simultaneously obtain the pieces that are constructible from four-dimensional unitarity cuts and the rational pieces that are missed by them, while retaining a helicity formalism. We illustrate the procedure using four- and five-point one-loop amplitudes in QCD, including examples with external fermions. We also demonstrate the technique’s effectiveness in next-to-leading order QCD corrections to Higgs processes by computing the next-to-leading order correction to the Higgs plus three positive-helicity gluons amplitude in the large top-quark mass limit.

We study the discovery potential of the minimal universal extra dimension model (MUED) and improve it by utilizing the $\mathrm{\text{multijet}}+\mathrm{\text{lepton}}$ mode at the LHC. Since the MUED has a nearly degenerate spectrum, most events only have soft jets and small $E_T^{\mathrm{miss}}$. The signature is challenging to search. We apply $M_{T2}$ for the event selection and set the invisible particle mass of $M_{T2}$ (test mass) to zero. The test mass is much smaller than the invisible particle mass of MUED. In that case, $M_{T2}$ of the signal can be large depending on up-stream radiation which includes initial state radiation. On the other hand, $M_{T2}$ of the background is mainly below the top quark mass. Hence, the signal is extracted from the background in the high $M_{T2}$ region. Since we use the leading jets for $M_{T2}$, there is a combinatorics effect. We find that the effect also enhances the signal to background ratio for high $M_{T2}$. We perform a detailed simulation with the matrix element correction to the QCD radiations. The discovery potential of the MUED is improved by the $M_{T2}$ cut, and the improvement is especially significant for the most degenerate parameter we consider, $\Lambda R=10$.

We discuss a consistency test which makes it possible to discriminate unknown nuclear background lines from neutrinoless double beta decay with only one isotope. By considering both the transition to the ground state and to the first excited $0^{+}$ state, a sufficiently large detector can reveal if neutrinoless double beta decay or some other nuclear physics process is at work. Such a detector could therefore simultaneously provide a consistency test for a certain range of Majorana masses and be sensitive to lower values of the effective Majorana mass $⟨m_{{\nu }_e}⟩$.

The electroweak contributions to the forward-backward asymmetry in the production of top-quark pairs at the Tevatron are evaluated at $\mathcal{O}({\alpha }^2)$ and $\mathcal{O}(\alpha {\alpha }_s^2)$. We perform a detailed analysis of all partonic channels that produce an asymmetry and combine them with the QCD contributions. They provide a non-negligible addition to the QCD-induced asymmetry with the same overall sign, thus enlarging the standard model prediction and diminishing the observed deviation. For the observed mass-dependent forward-backward asymmetry a $3\sigma$ deviation still remains at an invariant-mass cut of $M_{t\overline{t}}>450\mathrm{GeV}$.

We present the results of a Dalitz plot analysis of $D^0\to K_S^0{\pi }^0{\pi }^0$ using the CLEO-c data set of $818{\mathrm{pb}}^{-1}$ of $e^{+}{e}^{-}$ collisions accumulated at $\sqrt{s}=3.77\mathrm{GeV}$. This corresponds to $3\times {10}^6$ $D^0{\overline{D}}^0$ pairs from which we select 1259 tagged candidates with a background of $7.5\pm 0.9$ percent. Several models have been explored, all of which include the $K^{*}(892)$, $K_2^{*}(1430)$, $K^{*}(1680)$, the $f_0(980)$, and the $\sigma (500)$. We find that the combined ${\pi }^0{\pi }^0$ $S$-wave contribution to our preferred fit is $(28.9\pm 6.3\pm 3.1)\%$ of the total decay rate while $D^0\to {\overline{K}}^{*}(892{)}^0{\pi }^0$ contributes $(65.6\pm 5.3\pm 2.5)\%$. Using three tag modes and correcting for quantum correlations we measure the $D^0\to K_S^0{\pi }^0{\pi }^0$ branching fraction to be $(1.058\pm 0.038\pm 0.073)\%$.