Related papers: The non-topological $Z^\prime$ string in the 331 m…
We study the cosmological constant problem in a three-dimensional N=2 supergravity theory with gauge group SU[2]_{global}xU[1]_{local}. The model we consider is known to admit string-like configurations, the so-called semi-local cosmic…
We present the formation of metastable cosmic strings (CSs) in the context of a supersymmetric (SUSY) left-right model. The SU(2)R symmetry breaking occurs during a stage of T-model (Higgs) inflation (TI) driven by an SU(2)R triplet…
Quasi--realistic heterotic-string models in the free fermionic formulation typically contain an anomalous U(1), which gives rise to a Fayet-Iliopolous term that breaks supersymmetry at the one--loop level in string perturbation theory.…
We consider the minimal U(1)$^\prime$ extension of the Standard Model (SM) with conformal invariance at the classical level, where in addition to the SM particle contents, three generations of right-handed neutrinos and a U(1)$^\prime$…
String theory has no parameter except the string scale $M_S$, so the Planck scale $M_\text{Pl}$, the supersymmetry-breaking scale, the EW scale $m_\text{EW}$ as well as the vacuum energy density (cosmological constant) $\Lambda$ are to be…
We study the fate of U(1) strings embedded in a non-Abelian gauge theory with a hierarchical pattern of the symmetry breaking: G->U(1) at V->nothing at v, V>>v. While in the low-energy limit the Abrikosov-Nielsen-Olesen string (flux tube)…
In this talk, I discuss our recent work concerning the construction of non-supersymmetric heterotic string models which have exponentially suppressed dilaton tadpoles and cosmological constants, and thus greatly enhanced stability…
We map the parameter space that leads to stable Z-vortices in the electroweak model. For $sin^2 \theta_W = 0.23$, we find that the strings are unstable for a Higgs mass larger than 24 GeV. Given the latest constraints on the Higgs mass from…
In the minimal standard model we discuss stability of the Z-string configuration, which includes the zero mode connected with the broken gauge symmetry. The zero mode induces charge and current on the string and gives backreaction to the…
We investigate the implications of the nontrivial vacuum structure of little Higgs models. In particular, focusing on the littlest Higgs model, we demonstrate the existence of three types of topological defects. One is a global cosmic…
Semilocal and electroweak strings are well-known to be unstable against unwinding by the condensation of the second Higgs component in their cores. A large class of current models of dark matter contains dark scalar fields coupled to the…
We establish the existence of a static, classically stable string solution in a region of parameters of the generic two-Higgs Standard Model. In an appropriate limit of parameters, the solution reduces to the well-known soliton of the O(3)…
Metastable strings can arise from a two-step symmetry breaking chain of the type $SU(2) \to U(1) \to 1$.They can decay through quantum tunneling by nucleating a monopole-antimonopole pair, and are prominent candidates for explaining the…
Requiring that supersymmetric SU(5) and SU(6) grand unifications in the heterotic string theory must have 3 chiral families, adjoint (or higher representation) Higgs fields in the grand unifiedgauge group, and a non-abelian hidden sector,…
We develop a formalism for the quantization of topologically stable excitations in the 4-dimensional abelian lattice gauge theory. The excitations are global and local (Abrikosov-Nielsen-Olesen) strings and monopoles. The operators of…
We consider a class of heterotic N=2 -> 0 super no-scale Z_2-orbifold models. An appropriate stringy Scherk-Schwarz supersymmetry breaking induces tree level masses to all massless bosons of the twisted hypermultiplets and therefore…
We study a simple axionlike model with a charged scalar $\phi$ and a double-charged scalar $\zeta$ of global $U(1)$ symmetry. A particular feature of our model is that a vacuum manifold is a torus knot. We consider a hierarchical…
Three generation heterotic-string vacua in the free fermionic formulation gave rise to models with solely the MSSM states in the observable Standard Model charged sector. The relation of these models to Z_2 x Z_2 orbifold compactifications…
We consider coupled gravitational and electromagnetic perturbations of a family of five-dimensional Einstein-Maxwell solutions that describes both magnetized black strings and horizonless topological stars. We find that the odd…
It has been shown that the Dimopoulos-Wilczek (or missing-VEV) mechanism for doublet-triplet splitting can be implemented in $SU(5) \times SU(5)$ models, which requires no adjoint Higgs fields. This is an advantage from the point of view of…