We study the prospects and opportunities of a large muon electric dipole moment (EDM) of the order $({10}^{-24}–{10}^{-22})\mathrm{ecm}$. We investigate how natural such a value is within the general minimal supersymmetric extension of the standard model with $CP$ violation from lepton flavor violation in view of the experimental constraints. In models with hybrid gauge-gravity-mediated supersymmetry breaking, a large muon EDM is indicative for the structure of flavor breaking at the Planck scale, and points towards a high messenger scale.

In this work we use the Schwinger-Dyson equations to study the possibility that an enhanced gravitational attraction triggers the formation of a right-handed neutrino condensate, inducing dynamical symmetry breaking and generating a Majorana mass for the right-handed neutrino at a scale appropriate for the seesaw mechanism. The composite field formed by the condensate phase could drive an early epoch of inflation. We find that to the lowest order, the theory does not allow dynamical symmetry breaking. Nevertheless, thanks to the large number of matter fields in the model, the suppression by additional powers in $G$ of higher order terms can be compensated, boosting them up to their lowest order counterparts. This way chiral symmetry can be broken dynamically and the infrared mass generated turns out to be in the expected range for a successful seesaw scenario.

We consider the leading large string tension correction to correlation functions of three vertex operators of particular massive string states in ${\mathrm{AdS}}_5\times S^5$ string theory. We assume that two of these states are “heavy” carrying large spins (of order string tension) and thus can be treated semiclassically while the third state is “light” having fixed quantum numbers. We study several examples. In the case when the “heavy” states are described by a folded string with large-spin in ${\mathrm{AdS}}_5$ the 3-point function scales as a semiclassical spin parameter of the “heavy” state in power of the string level of the “light” massive string state. We observe similar behavior in the case of “heavy” states which admit a small angular momentum limit, which may thus represent creatures of three quantum massive string states.

We study the aspects of the fermion and gauge boson sectors in $SU(4{)}_L\times U(1{)}_X$ models with a little Higgs mechanism. We introduce a new setup of fermions, which ensures the cancellation of gauge anomaly and the cancellation of one-loop quadratic divergence to the Higgs mass for all fermion multiplets and gauge bosons. We explicitly present the interactions between the standard model fermions and the heavy gauge bosons to discuss the phenomenological implications of extra $Z^{\prime }$ and $Z^{\prime \prime }$ gauge bosons based on recent experimental data.

The nonperturbative electron-positron pair production (Schwinger effect) is considered for space- and time-dependent electric fields $\overrightarrow{E}(\overrightarrow{x},t)$. Based on the Dirac-Heisenberg-Wigner formalism, we derive a system of partial differential equations of infinite order for the 16 irreducible components of the Wigner function. In the limit of spatially homogeneous fields the Vlasov equation of quantum kinetic theory is rediscovered. It is shown that the quantum kinetic formalism can be exactly solved in the case of a constant electric field $E(t)=E_0$ and the Sauter-type electric field $E(t)=E_0{\mathrm{sech}}^2(t/\tau )$. These analytic solutions translate into corresponding expressions within the Dirac-Heisenberg-Wigner formalism and allow to discuss the effect of higher derivatives. We observe that spatial field variations typically exert a strong influence on the components of the Wigner function for large momenta or for late times.

On Moyal space-time, one can implement twisted Poincaré symmetry with the resultant modification of symmetrization and antisymmetrization postulates for bosons and fermions. We develop the thermofield approach of Umezawa and Takahashi on such a space-time preserving the twisted Poincaré symmetry of the underlying quantum field theory (qft). Implications of this twisted Poincaré symmetry for qft’s at finite temperature are pointed out.

We model the classical transmission of a massless scalar field from a source to a detector on a background causal set. The predictions do not differ significantly from those of the continuum. Thus, introducing an intrinsic inexactitude to lengths and durations—or more specifically, replacing the Lorentzian manifold with an underlying discrete structure—need not disrupt the usual dynamics of propagation.

We show a uniqueness theorem for Kaluza-Klein black holes in the bosonic sector of five-dimensional minimal supergravity. More precisely, under the assumptions of the existence of two commuting axial isometries and a nondegenerate connected event horizon of the cross-section topology $S^3$, or lens space, we prove that a stationary charged rotating Kaluza-Klein black hole in five-dimensional minimal supergravity is uniquely characterized by its mass, two independent angular momenta, electric charge, magnetic flux, and nut charge, provided that there exists neither a nut nor a bolt (a bubble) in the domain of outer communication. We also show that under the assumptions of the same symmetry, same asymptotics, and the horizon cross section of $S^1\times S^2$, a black ring within the same theory—if it exists—is uniquely determined by its dipole charge and rod intervals besides the charges and magnetic flux.

We introduce the formalism of quantum cosmology in a Friedmann-Lemaître-Robertson-Walker (FLRW) universe of arbitrary dimension filled with a perfect fluid with $p=\alpha \rho$ equation of state. First we show that the Schutz formalism, developed in four dimensions, can be extended to a $n$-dimensional universe. We compute the quantum representant of the scale factor $a(t)$, in the Many-Worlds, as well as, in the de Broglie-Bohm interpretation of quantum mechanics. We show that the singularities, which are still present in the $n$-dimensional generalization of FLRW universe, are excluded with the introduction of quantum theory. We quantize, via the de Broglie-Bohm interpretation of quantum mechanics, the components of the Riemann curvature tensor in a tetrad basis in a $n$-dimensional FLRW universe filled with radiation ($p=\frac{1}{n-1}\rho$). We show that the quantized version of the Ricci scalar are perfectly regular for all time $t$. We also study the behavior of the energy density and pressure and show that the ratio $⟨p{⟩}_L/⟨\rho {⟩}_L$ tends to the classical value $1/(n-1)$ only for $n=4$, showing that $n=4$ is somewhat privileged among the other dimensions. Besides that, as $n\to \infty$, $⟨p{⟩}_L/⟨\rho {⟩}_L\to 1$.

We investigate the formation of caustics in the Dirac-Born-Infeld type scalar field systems for generic classes of potentials, viz., massive rolling scalar with potential, $V(\varphi )=V_0{e}^{\pm (1/2)M^2{\varphi }^2}$ and inverse power-law potentials with $V(\varphi )=V_0/{\varphi }^n$, $0<n<2$. It is found that in the case of exponentially decreasing rolling massive scalar field potential, there are multivalued regions and regions of likely to be caustics in the field configuration. However there are no caustics in the case of exponentially increasing potential. We show that the formation of caustics is inevitable for the inverse power-law potentials under consideration in Minkowski space time whereas caustics do not form in this case in the Friedmann-Robertson-Walker Universe.

Models of galaxy and halo clustering commonly assume that the tracers can be treated as a continuous field locally biased with respect to the underlying mass distribution. In the peak model pioneered by Bardeen et al. [Astrophys. J. 304, 15 (1986)], one considers instead density maxima of the initial, Gaussian mass density field as an approximation to the formation site of virialized objects. In this paper, the peak model is extended in two ways to improve its predictive accuracy. First, we derive the two-point correlation function of initial density peaks up to second order and demonstrate that a peak-background split approach can be applied to obtain the $k$-independent and $k$-dependent peak bias factors at all orders. Second, we explore the gravitational evolution of the peak correlation function within the Zel’dovich approximation. We show that the local (Lagrangian) bias approach emerges as a special case of the peak model, in which all bias parameters are scale independent and there is no statistical velocity bias. We apply our formulas to study how the Lagrangian peak biasing, the diffusion due to large scale flows, and the mode coupling due to nonlocal interactions affect the scale dependence of bias from small separations up to the baryon acoustic oscillation (BAO) scale. For $2\sigma$ density peaks collapsing at $z=0.3$, our model predicts a $\sim 5\%$ residual scale-dependent bias around the acoustic scale that arises mostly from first order Lagrangian peak biasing (as opposed to second order gravity mode coupling). We also search for a scale dependence of bias in the large scale autocorrelation of massive halos extracted from a very large $N$-body simulation provided by the MICE Collaboration. For halos with mass $M\gtrsim {10}^{14}{\mathrm{M}}_{\odot }/h$, our measurements demonstrate a scale-dependent bias across the BAO feature which is very well reproduced by a prediction based on the peak model.

A particle cascade (shower) in a dielectric, for example, as initiated by an ultra-high-energy cosmic ray, will have an excess of electrons which will emit coherent Čerenkov radiation, known as the Askaryan effect. In this work we study the case in which such a particle shower occurs in a medium just below its surface. We show, for the first time, that the radiation transmitted through the surface is independent of the depth of the shower below the surface when observed from far away, apart from trivial absorption effects. As a direct application we use the recent results of the NuMoon project, where a limit on the neutrino flux for energies above ${10}^{22}\mathrm{eV}$ was set using the Westerbork Synthesis Radio Telescope by measuring pulsed radio emission from the Moon, to set a limit on the flux of ultra-high-energy cosmic rays.

A light Higgs boson is preferred by $M_W$ and $m_t$ measurements. A complex scalar singlet addition to the standard model allows a better fit to these measurements through a new light singlet dominated state. It then predicts a light dark matter (DM) particle that can explain the signals of DM scattering from nuclei in the CoGeNT and DAMA/LIBRA experiments. Annihilations of this DM in the galactic halo, $AA\to b\overline{b}$, $c\overline{c}$, ${\tau }^{+}{\tau }^{-}$, lead to gamma rays that naturally improve a fit to the Fermi Large Area Telescope data in the central galactic regions. The associated light neutral Higgs boson may also be discovered at the Large Hadron Collider.

We have studied the $\varphi (1020)a_0(980)$ $S$-wave scattering at threshold energies employing chiral Lagrangians coupled to vector mesons by minimal coupling. The interaction is described without new free parameters by considering the scalar isovector $a_0(980)$ resonance as dynamically generated in coupled channels and demanding that the recently measured $e^{+}{e}^{-}\to \varphi (1020)f_0(980)$ cross section is reproduced. For some values of a parameter obtained by fitting the latter reaction cross section, and taking the $a_0(980)$ pole position and residues from two previous studies, the presence of a dynamically generated isovector companion of the $Y(2175)$ is revealed. We have also investigated the corrections to the $e^{+}{e}^{-}\to \varphi (1020){\pi }^0\eta$ cross section that arise from $\varphi (1020)a_0(980)$ rescattering in the final state. They are large and lead to considerable modifications of the cross section in absolute value and energy dependence. Moreover, when a $\varphi (1020)a_0(980)$ resonance is present, it shows up as a clear resonant peak at $\sqrt{s}\sim 2.03\mathrm{GeV}$ in $e^{+}{e}^{-}\to \varphi (1020){\pi }^0\eta$ from the $\varphi (1020)a_0(980)$ final-state interactions.

We present a formula for reducing the rank of Wilson fermions from $4N_c{N}_x{N}_y{N}_z{N}_t$ to $4N_c{N}_x{N}_y{N}_z$ keeping the value of its determinant. We analyze eigenvalues of a reduced matrix and coefficients $C_n$ in the fugacity expansion of the fermion determinant $\sum _n{C}_n(\exp (\mu /T){)}^n$, which play an important role in the canonical formulation, using lattice QCD configurations on a $4^4$ lattice. Numerically, $\log |C_n|$ varies as $N_x{N}_y{N}_z$, and goes easily over the standard numerical range. We give a simple cure for that. The phase of $C_n$ correlates with the distribution of the Polyakov loop in the complex plain. These results lay the groundwork for future finite density calculations in lattice QCD.

We deal with the problem of assigning electromagnetic moments to a quasistable particle (i.e., a particle with mass located at the particle’s decay threshold). In this case, an application of a small external electromagnetic field changes the energy in a nonanalytic way, which makes it difficult to assign definitive moments. On the example of a spin-$1/2$ field with mass $M_{*}$ interacting with two fields of masses $M$ and $m$, we show how a conventionally defined magnetic dipole moment diverges at $M_{*}=M+m$. We then show that the conventional definition makes sense only when the values of the applied magnetic field $B$ satisfy $|eB|/2M_{*}\ll |M_{*}-M-m|$. We discuss implications of these results to existing studies in electroweak theory, chiral effective-field theory, and lattice QCD.

We consider string realizations of the Randall-Sundrum effective theory for electroweak symmetry breaking and explore the search for the lowest massive Regge excitation of the gluon and of the extra (color singlet) gauge boson inherent in D-brane constructions. In these curved backgrounds, the higher-spin Regge recurrences of standard model fields localized near the IR brane are warped down to close to the TeV range and hence can be produced at collider experiments. Assuming that the theory is weakly coupled, we make use of four gauge boson amplitudes evaluated near the first Regge pole to determine the discovery potential of LHC. We study the inclusive dijet mass spectrum in the central rapidity region $|y_{\mathrm{jet}}|<1.0$ for dijet masses $M\ge 2.5\mathrm{TeV}$. We find that with an integrated luminosity of $100{\mathrm{fb}}^{-1}$, the $5\sigma$ discovery reach can be as high as 4.7 TeV. Observations of resonant structures in $pp\to \mathrm{\text{direct}}\gamma +\mathrm{\text{jet}}$ can provide interesting corroboration for string physics up to 3.0 TeV. We also study the ratio of dijet mass spectra at small and large scattering angles. We show that with the first ${\mathrm{fb}}^{-1}$ such a ratio can probe lowest-lying Regge states for masses $\sim 2.5\mathrm{TeV}$.

Present and future ultra-high-energy-cosmic-ray facilities (e.g., the South and North components of the Pierre Auger Observatory) and TeV-gamma-ray telescope arrays (e.g., HESS and CTA) have the potential to set stringent bounds on the nine Lorentz-violating parameters of nonbirefringent modified Maxwell theory minimally coupled to standard Dirac theory. A concrete example is given how to obtain, in the coming decennia, two-sided bounds on the eight anisotropic parameters at the ${10}^{-20}$ level and an upper (lower) bound on the single isotropic parameter at the $+{10}^{-20}$ ($-{10}^{-16}$) level. Comparison is made with existing and potential direct bounds from laboratory experiments.

We study holographic renormalization for three-dimensional new massive gravity. By studying the general falloff conditions for the metric allowed by the model at infinity, we show that at the critical point where the central charges of the dual conformal field theory (CFT) are zero, it contains a leading logarithmic behavior. In the context of AdS/CFT correspondence it can be identified as a source for an irrelevant operator in the dual CFT. The presence of the logarithmic falloff may be interpreted as the fact that the dual CFT would be a logarithmic conformal field theory.

Ultralight scalar fields, with masses of between $m={10}^{-33}\mathrm{eV}$ and $m={10}^{-22}\mathrm{eV}$, can affect the growth of structure in the Universe. We identify the different regimes in the evolution of ultralight scalar fields, how they affect the expansion rate of the Universe, and how they affect the growth rate of cosmological perturbations. We find a number of interesting effects, discuss how they might arise in realistic scenarios of the early universe, and comment on how they might be observed.