Pliska Studia Mathematica Bulgarica

Volume 15, 2003



SG Pseudodifferential Operators and Weak Hyperbolicity
F. Nicola
L. Rodino

2000 Math. Subj. Classification:35S05, 47G30, 58J42.
Key words: Pseudo-differential operators, trace functionals, weak hyperbolicity.

Crack Theory with Singularities at the Boundary
B.-W. Schulze

2000 Math. Subj. Classification:5S15, 35J70, 35J40, 38J40.
Key words: Pseudo-differential boundary problems, mixed elliptic problems with singular interfaces, corner operators, weighted corner.

Hypoellipticity of Anisotropic Partial Differential Equations
Giuseppe De Donno

2000 Math. Subj. Classification:35S05.
Key words: Partial differential equations, hypoellipticity, Gevrey spaces.

Anomalous Singularities for Hyperbolic Equations with Degeneracy of Infinite Order
Michael Dreher

2000 Math. Subj. Classification: 35L80.
Key words: Weakly hyperbolic equations, propagation of singularities, lacunas, loss or regularity.

Gevrey Local Solvability for Semilinear Partial Differential Equations
Alessandro Oliaro

2000 Math. Subj. Classification: 35S05
Key words: Operators with multiple characteristics, Gevrey classes, local solvability.

About Strictly Hyperbolic Operators with Non-regular Coefficients
Michael Reissig

2000 Math. Subj. Classification:35L15, 35L80, 35S05, 35S30.
Key words: Strictly hyperbolic Cauchy problems, non-Lipschitz coefficients in time, classes of well-posedness, construction of parametrix, refined perfect diagonalization procedure, regularization techniques,  sharp G\aa rding's inequality.

Diagonalizable Complex Systems, Reduced Dimension and Hermitian Systems II
Jean Vaillant

2000 Math. Subj. Classification: 35L40.
Key words: Strong hyperbolicity, symmetric, hermitian systems.

Nonlinear Estimates in Anisotropic Gevrey Spaces
Lucio Cadeddu
Todor Gramchev

2000 Math. Subj. Classification: 35G20, 47H30.
Key words: Anisotropic Gevrey classes, nonlinear composition estimates, evolution PDE.

On Principle Eigenvalue for Linear Second Order Elliptic Equations in Divergence Form
A. Fabricant
N. Kutev
T. Rangelov

2000 Math. Subj. Classification: 35J15, 35J25, 35B05, 35B50.
Key words: Elliptic equations, maximum and comparison principle, eigenvalue problem.

Riccati Representation for Elements in H^{-1}(\T) and its Applications
Thomas Kappeler
Peter Topalov

2000 Math. Subj. Classification: 35L05, 34L15, 35D05, 35Q53.
Key words: Hill operator, Riccati transform, Birkhoff coordinates, KdV.

On the Zeros of the Solutions to Nonlinear Hyperbolic Equations with Delays
Z. A. Petrova
D. P. Mishev

2000 Math. Subj. Classification: 35B05, 35L15.
Key words: Hyperbolic equation, characteristic initial value problem, oscillation, eventually positive solution, eventually negative solution