1. Introduction
In this work, we study the approximate controllability of the following system with
unbounded delay, non-instantaneous impulse, and non-local condition. To achieve our result
we will use a technique developed by A. Bashirov et al. (Bashirov & Ghahramanlou, 2014;
Bashirov & Jneid, 2013; Bashirov, Mahmudov, Şemi, & Etikan, 2007), which does not use fixed
point theorems as many researchers do. On the other hand, as the delay is infinite, we consider
a phase space that satisfies the axiomatic theory propose by Hale-Kato to study retarded
differential equations with unbounded delay (Hale & Kato, 1978; Hino, Murakami, & Naito,
2013). These results prove once again that the controllability of a linear system is preserved if
we consider the impulses, the non-local conditions and the delays as disturbances of it, which
is very natural in real life problems, never the critical points of a differential equation is exactly
the critical point of the model that it represents, the same happens with the impulses, the delay
and non-local conditions; they are intrinsic phenomena to the real problem, that many times
they are not taken into account at the moment of carrying out the mathematical modeling:
(1.1)
where , , , .
There exists a fixed number such that , where is the maximal interval
of local existence of solutions of problem (1.1); and , , selected
under specific rules marked by the real-life problem that the mathematical model could
represent, such as:
. The advantage of using non-local conditions is that
measurements at more places can be incorporated to get better models. For more details and
physical interpretations see Byszewski & Lakshmikantham (1991), Byszewski (1990),
Byszewski (1991), Chabrowski (1984), Vrabie (2015), and references therein. ,
, is the phase space to be specified later. , is a
smooth enough function, , are continuous and represents the
impulsive effect in the system (1.1), i.e., we are considering that the system can have abrupt
changes that stay there for an interval of time. These alterations in state might be due to certain
external factors, which cannot be well described by pure ordinary differential equations, (see,
for instance, Lakshmikantham, Bainov, & Simeonov (1989) and Selvi & Arjunan (2012) and
reference therein). , and , where is the phase space that will
be defined later (see section 2). For this type of problems the phase space for initial functions
plays an important role in the study of both qualitative and quantitative theory, for more
details, in case without impulses and non-local conditions, we refer to Hale & Kato (1978), Hino
et al. (2013) and Shin (1987, 1987). The function for illustrate the