## LPi Logic with Fixed Points

We study a system, $\mu$L$\Pi$, obtained by an expansion of  L$\Pi$ logic with fixed points connectives. The first main result of the paper is that $\mu$L$\Pi$ is standard complete, i.e. complete with regard to the unit interval of real numbers endowed with a suitable structure.
We also prove that the class of algebras which forms algebraic semantics for this logic is generated, as a variety, by its linearly ordered members and that they are precisely the interval algebras of real closed fields. This correspondence is extended to a categorical equivalence between the whole category of those algebras and another category naturally arising from real closed fields.
Finally, we show that this logic enjoys implicative interpolation.

LPi Logic with Fixed Points

## muMV-algebras: an approach to fixed points in Lukasiewicz logic

We study an expansion of MV-algebras, called $\mu$MV-algebras, in which minimum and maximum fixed points are definable. The first result is that $\mu$MV-algebras are term-wise equivalent to divisible MV$_\Delta$ algebras, i.e. a combination of two known MV-algebras expansion: divisible MV-algebras and MV$_\Delta$ algebras. Using methods from the two known extensions we derive a number of results about $\mu$MV-algebras; among others: subdirect representation, standard completeness, amalgamation property and a description of the free algebra.

muMV-algebras: an approach to fixed points in Lukasiewicz logic