Hot nuclear matter with dilatons

We study hot nuclear matter in a model based on nucleon interactions deriving from the exchange of scalar and vector mesons. The main new feature of our work is the treatment of the scale breaking of quantum chromodynamics through the introduction of a dilaton field. Although the dilaton effects are quite small quantitatively, they affect the high-temperature phase transition appreciably. We find that inclusion of the dilaton leads to a metastable high-density state at zero pressure, similar to that found by Glendenning who considered instead the admixture of higher baryon resonances.Comment: 10 pages, LaTeX with equation.sty (optional) and epsfig.sty, 11 figures packed with uufiles. Final, published version (small changes from original preprint

Nuclear matter and neutron matter for improved quark mass density- dependent model with ρ\rho mesons

A new improved quark mass density-dependent model including u, d quarks, $\sigma$ mesons, $\omega$ mesons and $\rho$ mesons is presented. Employing this model, the properties of nuclear matter, neutron matter and neutron star are studied. We find that it can describe above properties successfully. The results given by the new improved quark mass density- dependent model and by the quark meson coupling model are compared.Comment: 18 pages, 7 figure

Effective hadron masses and couplings in nuclear matter and incompressibility

The role of effective hadron masses and effective couplings in nuclear matter is studied using a generalized effective Lagrangian for sigma-omega model. A simple relation among the effective masses, the effective couplings and the incompressibility K is derived. Using the relation, it is found that the effective repulsive and the effective attractive forces are almost canceled to each other at the normal density. Inversely, if this cancellation is almost complete, K should be 250-350MeV.Comment: 13 pages of text, 16 figure

Algebrai struktúrák és algoritmusok = Algebraic structures and algorithms

A pályázat keretében három témakörben --- általános algebra, félcsoportelmélet és döntési problémák bonyolultsága --- nyertünk eredményeket. A kutatás jelentős része hazai, illetve külföldi kutatókkal való együttműködésben született. Bebizonyítottuk, hogy algebrák egy igen tág osztályában azokat a véges algebrákat, amelyek reziduálisan kicsi varietást generálnak, meghatározzák a c-változós kompatibilis relációi, ahol c csak az osztály egy paraméterétől és az alaphalmaz nagyságától függő konstans. Meghatároztuk a legfeljebb 4 többségi függvényt tartalmazó minimális klónokat, valamint azokat a minimális klónt generáló kétváltozós műveleteket, amelyek "majdnem asszociatívak". Általánosítottuk kvázivarietásokra Willard véges azonosságbázis tételét, és egy speciális esetben bebizonyítottuk Pigozzi relatív kongruenciamoduláris kvázivarietásokra vonatkozó véges azonosságbázis sejtését. Jellemeztük a kötegek csoportokkal vett szemidirekt szorzatainak idempotens-szétválasztó homomorf képeit, és ezek reguláris részfélcsoportjait. Bebizonyítottuk, hogy minden E-tömör lokálisan inverz félcsoport beágyazható teljesen egyszerű félcsoport inverz félcsoporttal vett lambda-szemidirekt szorzatába. Algebrai és kombinatorikai jellegű feltételeket adtunk arra, hogy egy lokálisan véges varietás típushalmaza nem tartalmaz 1-es típust, illetve 1-es és 2-es típust. Dichotómiatételt bizonyítottunk polinom-egyenletrendszerek megoldhatóságára olyan algebrák felett, melyek "kizárják" az 1-es típust. | The results of the project belong to three areas: universal algebra, semigroup theory and complexity theory. Most of the research was carried out in international cooperation. We proved that in a wide class of algebras, the finite algebras that generate residually small varieties are determined by their c-ary compatible relations where c is a constant that depends only on a parameter of the class and on the size of the underlying set. We described the minimal clones with at most 4 majority operations, and those binary operations generating a minimal clone which are "almost associative". We generalized the finite basis theorem of Willard to quasivarieties, and proved a conjecture of Pigozzi regarding the finite axiomatizability of relative congruence-modular quasivarieties in a special case. We characterized the idempotent separating homomorphic images of semidirect products of bands by groups, and their regular subsemigroups. We proved that each E-solid locally inverse semigroup is embeddable in a lambda-semidirect product of a completely simple semigroup by an inverse semigroup. We gave algebraic and combinatorial characterizations of the locally finite varieties omitting type 1 and of those omitting types 1 and 2. We proved a dichotomy theorem for the solvability problem of systems of polynomial equations over certain finite algebras

Algebraosztályok és klónok = Classes of algebras and clones

Főbb eredményeink a következők. Beláttuk, hogy többségi kifejezésfüggvény létezése eldönthető véges algebrákra. Igazoltuk, hogy bármely nem-triviális idempotens Malcev-feltételt teljesítő véges algebrának van gyenge többségi kifejezésfüggvénye, és 2-uniform kongruenciái felcserélhetőek. Bizonyítottuk, hogy a k-parallelogramma-kifejezéssel rendelkező véges, reziduálisan kicsi algebrák és a véges 2-nilpotens csoportok kifejezésfüggvényeinek klónját véges sok reláció meghatározza. Új dichotómiatételeket kaptunk a kényszer-kielégíthetőségi problémára és az egyenletrendszer-megoldhatósági problémára. Számos új eredményt kaptunk hálók kombinatorikai vonatkozásairól, fraktál- és féligmoduláris hálókról. Struktúratételeket bizonyítottunk az E-tömör lokálisan inverz félcsoportokra, az E-unitér majdnem faktorizálható ortodox félcsoportokra, valamint kiterjesztettük a majdnem faktorizálható inverz félcsoportok elméletét a lokálisan inverz félcsoportok osztályára. Jellemeztünk bizonyos transzformáció-monoidokat, amelyek egyelemű monadikus intervallumot határoznak meg a klónhálóban. Leírtuk a centralizátorklónt véges, egyszerű, idempotens algebrák és bizonyos kongruencia disztributív varietást generáló véges algebrák esetén. Új eredményeket kaptunk 3-változós többségi függvénnyel rendelkező minimális klónokra. Beláttuk, hogy a kompozícióra zárt függvényosztályok hálója kontinuum számosságú a kételmű halmazon, és leírtuk e háló szerkezetét. | Our main results are as follows. We proved that the existence of a near-unanimity term operation is decidable for finite algebras. We showed that if a finite algebra admits a nontrivial idempotent Maltsev condition, then it has a weak near-unanimity term operation, and its 2-uniform congruences permute. We proved that the clone of any finite residually small algebra with a k-parallelogram term operation and any finite 2-nilpotent group is determined by finitely many relations. We obtained new dichotomy theorems for the constraint satisfaction problem and for the solvability problem of systems of equations. We proved a number of theorems on the combinatorial aspects of lattices and on fractal and semimodular lattices. We obtained new structure theorems for E-solid locally inverse semigroups and E-unitary almost factorizable orthodox semigroups. Furthermore we extended the theory of almost factorizable inverse semigroups to the class of locally inverse semigroups. We characterized certain transformation monoids which determine a one-element monoidal interval in the lattice of clones. We described the centralizer clones of finite simple idempotent algebras and of certain algebras in congruence distributive varieties. We obtained new results on the minimal clones containing majority operations. We proved that on the two-element set the lattice of function classes closed under composition has the cardinality of the continuum, and described the structure of this lattice

Finite Nuclei in a Relativistic Mean-Field Model with Derivative Couplings

We study finite nuclei, at the mean-field level, using the Zimanyi-Moskowski model and one of its variations (the ZM3 model). We calculate energy levels and ground-state properties in nuclei where the mean-field approach is reliable. The role played by the spin-orbit potential in sorting out mean-field model descriptions is emphasized.Comment: 17 pages, 9 figures, 30 kbytes. Uses EPSF.TEX. To appear in Zeit. f. Phys. A (Hadrons and Nuclei

Hadrons in Dense Resonance-Matter: A Chiral SU(3) Approach

A nonlinear chiral SU(3) approach including the spin 3/2 decuplet is developed to describe dense matter. The coupling constants of the baryon resonances to the scalar mesons are determined from the decuplet vacuum masses and SU(3) symmetry relations. Different methods of mass generation show significant differences in the properties of the spin-3/2 particles and in the nuclear equation of state.Comment: 28 pages, 9 figure

Anatomy of a microearthquake sequence on an active normal fault

The analysis of similar earthquakes, such as events in a seismic sequence, is an effective tool with which to monitor and study source processes and to understand the mechanical and dynamic states of active fault systems. We are observing seismicity that is primarily concentrated in very limited regions along the 1980 Irpinia earthquake fault zone in Southern Italy, which is a complex system characterised by extensional stress regime. These zones of weakness produce repeated earthquakes and swarm-like microearthquake sequences, which are concentrated in a few specific zones of the fault system. In this study, we focused on a sequence that occurred along the main fault segment of the 1980 Irpinia earthquake to understand its characteristics and its relation to the loading-unloading mechanisms of the fault system

Structure of the Vacuum in Nuclear Matter - A Nonperturbative Approach

We compute the vacuum polarisation correction to the binding energy of nuclear matter in the Walecka model using a nonperturbative approach. We first study such a contribution as arising from a ground state structure with baryon-antibaryon condensates. This yields the same results as obtained through the relativistic Hartree approximation of summing tadpole diagrams for the baryon propagator. Such a vacuum is then generalized to include quantum effects from meson fields through scalar-meson condensates. The method is applied to study properties of nuclear matter and leads to a softer equation of state giving a lower value of the incompressibility than would be reached without quantum effects. The density dependent effective sigma mass is also calculated including such vacuum polarisation effects.Comment: 26 pages including 5 eps files, uses revtex style; PACS number: 21.65.+f,21.30.+