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We show that stable local cosmic strings are a generic prediction of supersymmetric models where supersymmetry is broken at scales within a few orders of magnitude of the weak scale and is fed down to the observable sector by gauge…
It is shown that it is possible for bound fermions on a cosmic string to form a superconducting state. Due to the attractive force between them, particles moving in opposite directions along the string form bound pairs. This involves a…
Models of symmetry breaking in the early universe can produce networks of cosmic strings threading 't Hooft-Polyakov monopoles. In certain cases there is a larger global symmetry group and the monopoles split into so-called semipoles. These…
We study Abelian strings in a fixed de Sitter background. We find that the gauge and Higgs fields extend smoothly across the cosmological horizon and that the string solutions have oscillating scalar fields outside the cosmological horizon…
We discuss magnetic monopole solutions of the Einstein-Yang-Mills-Higgs equations with a positive cosmological constant. These configurations approach asymptotically the de Sitter spacetime background and exist only for a nonzero Higgs…
We investigate cosmic strings arising from a hierarchical gauge symmetry breaking sequence, $\mathrm{SU}(2) \times \mathrm{U}(1) \rightarrow \mathrm{U}(1) \times \mathrm{U}(1) \rightarrow \mathrm{U}(1)' \rightarrow \text{Nothing}$. This…
We are discussing some aspects of the magnetic monopoles and cosmic strings interactions with axion domain walss and membranes. The monopole moving through an axion domain wall is transformed into a monopole bag - the state with a dyon…
The spontaneous breaking of $SO(10)$ via flipped $SU(5)$ to the Standard Model yields a novel scenario in which the superheavy topologically stable GUT monopole carrying a single unit ($2\pi/e$) of Dirac magnetic charge emerges from the…
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…
Aspects of string cosmology for critical and non-critical strings are discussed emphasizing the necessity to account for the dilaton dynamics for a proper incorporation of ``large - small" duality. This drastically modifies the intuition…
We argue that the existence of the electroweak monopole predicts the existence of the electroweak string in the standard model made of monopole-antimonopole pair separated infinitely apart, which carry the quantized magnetic flux $4 \pi…
It has been shown that 5-dimensional general relativity action extended by appropriate quadratic terms admits a singular superconducting cosmic string solution. We search for cosmic strings endowed with similar and extended physical…
We study the structure of cosmic strings produced at the breaking of an anomalous U(1) gauge symmetry present in many superstring compactification models. We show that their coupling with the axion necessary in order to cancel the anomalies…
There are at least two serious moduli problems in string cosmology. The first is the possibility that moduli dominate the energy density at the time of nucleosynthesis. The second is that they may not find their minima all together. After…
We consider grand unified theories with superconducting cosmic strings and which admit the mechanism for generating primordial magnetic fields recently discussed by Vachaspati. We show that these models are severely constrained by…
Yang-Mills theory is studied in a variant of 't Hooft's maximal Abelian gauge. In this gauge magnetic monopoles arise in the Abelian magnetic field. We show, however, that the full (non-Abelian) magnetic field does not possess any…
In supersymmetric theories, topological defects can have nontrivial behaviors determined purely by whether or not supersymmetry is restored in the defect core. A well-known example of this is that some supersymmetric cosmic strings are…
The cosmological constant is an unexplained until now phenomena of nature that requires an explanation through string effects. The apparent discrepancy between theory and experiment is enourmous and has already been explained several times…
The moduli of N=1 compactifications of IIB string theory can be stabilized by a combination of fluxes (which freeze complex structure moduli and the dilaton) and nonperturbative superpotentials (which freeze Kahler moduli), typically…
We discuss some recent work in the field of classical solitonic solutions in string theory. In particular, we construct instanton and monopole solutions and discuss the dynamics of string-like solitons. Some of the motivation behind this…