A Recipe for State Dependent Distributed Delay Differential Equations

We use the McKendrick equation with variable ageing rate and randomly distributed maturation time to derive a state dependent distributed delay differential equation. We show that the resulting delay differential equation preserves non-negativity of initial conditions and we characterise local stability of equilibria. By specifying the distribution of maturation age, we recover state dependent discrete, uniform and gamma distributed delay differential equations. We show how to reduce the uniform case to a system of state dependent discrete delay equations and the gamma distributed case to a system of ordinary differential equations. To illustrate the benefits of these reductions, we convert previously published transit compartment models into equivalent distributed delay differential equations.Comment: 28 page

Algebraic entropy for differential-delay equations

We extend the definition of algebraic entropy to a class of differential-delay equations. The vanishing of the entropy, as a structural property of an equation, signals its integrability. We suggest a simple way to produce differential-delay equations with vanishing entropy from known integrable differential-difference equations

Mixed stochastic delay differential equations

We consider a stochastic delay differential equation driven by a Holder continuous process and a Wiener process. Under fairly general assumptions on its coefficients, we prove that this equation is uniquely solvable. We also give sufficient conditions for finiteness of its moments and establish a limit theorem

Dissipativity of the delay semigroup

Under mild conditions a delay semigroup can be transformed into a (generalized) contraction semigroup by modifying the inner product on the (Hilbert) state space into an equivalent inner product. Applications to stability of differential equations with delay and stochastic differential equations with delay are given as examples

Delay differential equations

Tato bakalářská práce se zabývá problematikou diferenciálních rovnic se zpožděním, které na rozdíl od obyčejných diferenciálních rovnic, obsahují v argumentu neznámé funkce funkci tzv. zpoždění a díky tomu mohou přesněji popisovat některé reálné systémy, jenž se snažíme převést do matematického modelu. V praxi to jsou systémy, v nichž se vyskytují například časové prodlevy potřebné k reakci systému na změnu stavu.\\Přítomnost zpoždění je na druhou stranu komplikací při řešení těchto rovnic a příčinou mnoha odlišností od obyčejných rovnic, z nichž ty hlavní jsou v této práci popsané. Rovněž je ukázán princip použití diferenciálních rovnic se zpožděním při modelování růstu populací.Bachelor thesis focuses on the issue of differential equations with delay, which, unlike ordinary differential equations, contain in the unknown function argument the function of the so-called delay. Therefore, these are capable of a more exact description of certain real systems we want to convert into mathematic models. Practically, these are those systems where time delays, necessary for the reaction of the system to the change of status, occur. The presence of this delay, however, also complicates solution of such equations and sets further differences in comparison with ordinary equations. The crucial differences are described in this thesis. Also the principle is shown for the use of delay-differential equations in population growth models.