38 research outputs found
On Elliptical Billiards in the Lobachevsky Space and associated Geodesic Hierarchies
We derive Cayley's type conditions for periodical trajectories for the
billiard within an ellipsoid in the Lobachevsky space. It appears that these
new conditions are of the same form as those obtained before for the Euclidean
case. We explain this coincidence by using theory of geodesically equivalent
metrics and show that Lobachevsky and Euclidean elliptic billiards can be
naturally considered as a part of a hierarchy of integrable elliptical
billiards.Comment: 14 pages, to appear in Journal of Geometry and Physic
Ellipsoidal billiards in pseudo-Euclidean spaces and relativistic quadrics
We study geometry of confocal quadrics in pseudo-Euclidean spaces of an
arbitrary dimension and any signature, and related billiard dynamics. The
goal is to give a complete description of periodic billiard trajectories within
ellipsoids. The novelty of our approach is based on introduction of a new
discrete combinatorial-geometric structure associated to a confocal pencil of
quadrics, a colouring in colours, by which we decompose quadrics of
geometric types of a pencil into new relativistic quadrics of relativistic
types. Deep insight of related geometry and combinatorics comes from our study
of what we call discriminat sets of tropical lines and
and their singularities. All of that enable usto get an analytic criterion
describing all periodic billiard trajectories, including the light-like ones as
those of a special interest.Comment: 29 pages, 7 figure
New Examples of Systems of the Kowalevski Type
A new examples of integrable dynamical systems are constructed. An
integration procedure leading to genus two theta-functions is presented. It is
based on a recent notion of discriminantly separable polynomials. They have
appeared in a recent reconsideration of the celebrated Kowalevski top, and
their role here is analogue to the situation with the classical Kowalevski
integration procedure.Comment: 17 page
IstraživaÄko-edukacijsko srediÅ”te Prehrambeno-biotehnoloÅ”kog fakulteta SveuÄiliÅ”ta u Zagrebu smjeÅ”teno u Zadru
Godine 2006. osnovano je u okviru Prehrambeno-biotehnoloÅ”kog fakulteta SveuÄiliÅ”ta u Zagrebu MeÄunarodno edukacijsko-istraživaÄko srediÅ”te locirano u zgradi Fakulteta u Zadru. Za stavljanje u funkciju prostora koji je u to vrijeme bio devastiran i praktiÄki neupotrebljiv osigurana su sredstva uz znaÄajnu participaciju Grada Zadra i Zadarske županije Äime je omoguÄena izgradnja i opremanje laboratorija. Od 2010. godine u Centru se kontinuirano i sustavno provode brojne znanstveno-istraživaÄke aktivnosti koje obuhvaÄaju implementaciju razliÄitih kategorija projekata financiranih iz nacionalnih izvora te najveÄim dijelom iz fondova EU. UspjeÅ”nom implementacijom projekata ojaÄan je znanstveno istraživaÄki kapacitet Centra te infrastruktura kroz nabavu sofisticirane tehnoloÅ”ke te analitiÄke opreme i laboratorijskih ureÄaja. TakoÄer, u Centru se provode i istraživanja vezana uz izradu zavrÅ”nih, diplomskih i doktorskih radova te surednja s gospodarstvom
Systems of Hess-Appel'rot Type and Zhukovskii Property
We start with a review of a class of systems with invariant relations, so
called {\it systems of Hess--Appel'rot type} that generalizes the classical
Hess--Appel'rot rigid body case. The systems of Hess-Appel'rot type carry an
interesting combination of both integrable and non-integrable properties.
Further, following integrable line, we study partial reductions and systems
having what we call the {\it Zhukovskii property}: these are Hamiltonian
systems with invariant relations, such that partially reduced systems are
completely integrable. We prove that the Zhukovskii property is a quite general
characteristic of systems of Hess-Appel'rote type. The partial reduction
neglects the most interesting and challenging part of the dynamics of the
systems of Hess-Appel'rot type - the non-integrable part, some analysis of
which may be seen as a reconstruction problem. We show that an integrable
system, the magnetic pendulum on the oriented Grassmannian has
natural interpretation within Zhukovskii property and it is equivalent to a
partial reduction of certain system of Hess-Appel'rot type. We perform a
classical and an algebro-geometric integration of the system, as an example of
an isoholomorphic system. The paper presents a lot of examples of systems of
Hess-Appel'rot type, giving an additional argument in favor of further study of
this class of systems.Comment: 42 page
Determination of Phenolic Content and DPPH Radical Scavenging Activity of Functional Fruit Juices Fortified with Thymus serpyllum L. and Salvia officinalis L. Extracts
The objective of this study was to spectrophotometric determinate the total phenolic, flavonoid, hydroxycinnamic acid, and flavonol content of orange, pineapple, and apple juices fortified with wild thyme (Thymus serpyllum L.), Dalmatian sage (Salvia officinalis L.), and wild thyme-Dalmatian sage (3 : 1, v / v) extracts, and to evaluate their DPPH radical scavenging activity as a contribution to the development of a new functional beverage. The plant extracts addition increased the amount of phenolic compounds in fruit juices and improved their antioxidant properties. The highest concentrations of bioactive compounds and the greatest DPPH radical activity were obtained by adding Dalmatian sage extract to orange juice. Our study provides the novelty of fortifying fruit juices with wild thyme and Dalmatian sage extracts and offers significant potential for the creation of functional beverages
Systems of Hess-Appel'rot type
We construct higher-dimensional generalizations of the classical
Hess-Appel'rot rigid body system. We give a Lax pair with a spectral parameter
leading to an algebro-geometric integration of this new class of systems, which
is closely related to the integration of the Lagrange bitop performed by us
recently and uses Mumford relation for theta divisors of double unramified
coverings. Based on the basic properties satisfied by such a class of systems
related to bi-Poisson structure, quasi-homogeneity, and conditions on the
Kowalevski exponents, we suggest an axiomatic approach leading to what we call
the "class of systems of Hess-Appel'rot type".Comment: 40 pages. Comm. Math. Phys. (to appear