Ann.
Acad.
Rom.
Sci.
Ser.
Math.
Appl.
ISSN
2066-6594
Vol.
18,
No.
3/2026
ON
THE
SPRING
SESSION
OF
THE
ROMANIAN
ITINERANT
SEMINAR
ON
MATHEMATICS
AND
ITS
APPLICATIONS
(RISMA),
29
May
2026,
Bucharest,
ROMANIA
Gheorghe
MOROS
¸ANU
∗
Savin
TREANT
¸
˘
A
†
In
memory
of
Mihail
MEGAN
(1947-2025),
who
was
an
excellent
educator
and
talented
mathematician
Introduction
We
recall
that
the
Romanian
Itinerant
Seminar
on
Mathematics
and
Its
Applications
(RISMA)
was
launched
in
2024
by
Prof.
Gheorghe
Moro¸
sanu
(with
the
approval
of
the
ARS
leadership,
see
www.aosr.ro/en/romanian-
itinerant-seminar-on-mathematics-and-applications-sirma/),
as
a
natural
ex-
tension
of
the
former
Romanian
Itinerant
Seminar
on
Mathematical
Analysis
and
its
Applications
(RISMAA:
http://cs.ubbcluj.ro/rismaa).
Under
this
new
format,
the
RISMA
seminar
is
held
twice
a
year,
within
the
Spring
and
Autumn
Scientific
Conferences
organized
by
the
Academy
of
Romanian
Scientists
(ARS),
being
hosted
in
the
same
places,
during
the
same
time
slot.
Participants
to
RISMA
are
members
of
the
Mathematical
Sciences
Sec-
tion
of
the
ARS,
as
well
as
other
Romanian
and
foreign
researchers
inter-
ested
in
mathematics
and
its
applications.
More
specifically,
the
idea
was
to
extend
the
cooperation
of
our
ARS
colleagues
to
a
wider
community.
The
∗
gheorghe.morosanu@ubbcluj.ro
,
Department
of
Mathematics,
Babe¸
s-Bolyai
Univer-
sity,
Cluj-Napoca,
Romania
&
Academy
of
Romanian
Scientists,
Bucharest
†
savin.treanta@upb.ro
,
National
University
of
Science
and
Technology
PO-
LITEHNICA
Bucharest
&
Academy
of
Romanian
Scientists,
Bucharest
241
RISMA
Spring
Session,
29
May
2026,
Bucharest,
Romania
242
papers
resulting
from
this
seminar
are
usually
published
in
our
journal,
Ann.
Acad.
Rom.
Sci.
Ser.
Math.
Appl.
This
was
the
third
meeting
of
the
RISMA,
which
was
attended
by
several
participants,
including
9
presenters.
The
abstracts
of
the
presentations
are
attached
below,
listed
in
alpha-
betical
order
by
the
presenters
names.
Full
papers
may
be
obtained
by
contacting
the
authors
directly
at
the
email
addresses
provided.
•
Vasile
BERINDE
,
Technical
University
of
Cluj-Napoca,
North
Uni-
versity
Center
of
Baia
Mare,
Romania,
Full
Memeber
of
the
Academy
of
Romanian
Scientists;
email
address:
vasile.berinde@mi.utcluj.ro
Title:
Fixed
Point
Algorithms
in
Data
Science
Abstract
:
In
this
paper
we
present
some
aspects
related
to
the
con-
struction
of
fixed
point
algorithms
for
solving
Data
Science
problems.
•
Aurelian
CERNEA
,
University
of
Bucharest,
Romania,
Correspond-
ing
Member
of
the
Academy
of
Romanian
Scientists,
email
address:
ac-
ernea@fmi.unibuc.ro
Title:
Some
Classes
of
Differential
Inclusions
of
Fractional
Or-
der
Abstract
:
Two
classes
of
differential
inclusions
of
fractional
order
de-
fined
by
different
fractional
derivatives
(Hilfer-Hadamard,
and
generalized
Caputo)
and
with
several
boundary
conditions
are
studied.
All
the
prob-
lems
take
into
account
the
situation
when
the
set-valued
maps
are
not
con-
vex
valued.
The
existence
of
solutions
is
established
by
means
of
different
techniques.
•
Vasile
DR
˘
AGAN
,
Simion
Stoilow
Mathematics
Institute
of
the
Ro-
manian
Academy,
Full
Member
of
the
Academy
of
Romanian
Scientists,
and
Samir
ABERKANE
,
Universit´
e
de
Lorraine,
CRAN,
UMR
Vandoeuvre-
les-Nancy
Cedex,
France,
and
CNRS,
CRAN,
UMR
7039,
France;
email
addresses:
vasile.dragan@imar.ro,
samir.aberkane@univ-lorraine.fr
Title:
Exponential
Stability
in
Mean
Square
of
the
McKean-
Vlasov
Linear
Stochastic
Differential
Equations
G.
Moro¸
sanu,
S.
Treant
¸˘
a
243
Abstract
:
Our
aim
is
to
analyse
the
problem
of
the
exponential
sta-
bility
in
mean
square
of
a
class
of
McKean-Vlasov
type
stochastic
linear
differential
equations.
We
refer
to
stochastic
differential
equations
which
contain
besides
the
unknown
function
its
mean
value
and/or
its
conditional
expectation.
This
class
of
diferential
equations
is
known
in
the
literature
as
mean-field
stochastic
differential
equations
.
We
assume
that
the
initial
states
can
be
either
random
vectors
independent
of
the
Brownian
mo-
tion
or
adapted
to
the
filtration
generated
by
the
Brownian
motion
which
affects
the
dynamical
system
under
consideration,
or
deterministic
vectors.
We
show
that
without
loss
of
generality
we
can
characterize
the
exponential
stability
in
mean
square
property
of
the
zero
solution
of
a
McKean-Vlasov
linear
differential
equation
based
only
on
the
behavior
of
its
trajectories
which
are
starting
from
deterministic
states.
To
a
McKean-Vlasov
type
lin-
ear
differential
equation
is
associated,
in
a
natural
way,
a
standard
Itˆ
o
type
stochastic
linear
differential
equation.
In
many
already
published
works,
it
was
asserted
that
the
exponential
stability
in
mean
square
of
the
zero
solution
of
a
McKean-Vlasov
type
stochastic
linear
differential
equation
is
equivalent
to
the
exponential
stability
in
mean
square
of
the
zero
solution
of
the
associated
Itˆ
o
type
stochastic
linear
differential
equation.
We
show
that
equivalence
is
not
true
and
hence,
the
known
criteria
for
the
exponential
stability
in
mean
square
for
Itˆ
o
stochastic
linear
differential
equations
can
be
used
only
as
sufficient
conditions
for
exponential
stability
in
mean
square
of
the
zero
solution
of
the
McKean-Vlasov
stochastic
linear
differential
equa-
tions.
Also
we
show
that
based
on
the
structure
of
the
matrix
coefficients
of
the
associated
Itˆ
o
type
differential
equation,
we
may
derive
Lyapunov
criteria
of
lower
dimension
for
exponential
stability
in
mean
square
in
com-
parison
to
those
which
could
be
obtained
by
applying
directly
the
known
criteria
from
the
literature.
•
Teodor
HAV
ˆ
ARNEANU
and
C˘
at˘
alin
POPA
,
Octav
Mayer
Math-
ematics
Institute
in
Ia¸
si
of
the
Romanian
Academy,
Ia¸
si
Branch;
email
ad-
dresses:
havi@uaic.ro,
cpopa@uaic.ro
Title:
Boundary
Controllability
for
the
Two-Dimensional
Navier-
Stokes
Equations
with
Navier
Slip
Boundary
Conditions
Abstract
:
We
consider
the
following
Navier-Stokes
controlled
system,
denoted
(1),
∂y
∂t
−
∆
y
+
(
y
·
∇
)
+
∇
p
=
f,
in
Q
=
Ω
×
(0
,
T
)
RISMA
Spring
Session,
29
May
2026,
Bucharest,
Romania
244
div
(
y
)
=
0
,
in
Q
y
·
N
=
0
,
curl
(
y
)
=
0
,
on
Σ
=
∂
Ω
×
(0
,
T
)
y
=
u,
on
Σ
y
(
·
,
0)
=
y
0
(
·
)
,
in
Ω
,
where
Ω
⊂
R
2
ia
a
bounded
domain
with
the
boundary
∂
Ω
of
class
C
2
,
y
=
(
y
1
,
y
2
)
:
Q
→
R
2
is
the
velocity
of
the
fluid,
p
is
the
scalar
pressure,
u
:
Σ
→
R
2
is
the
boundary
control,
f
:
Q
→
R
2
is
the
density
of
the
external
forces
and
y
0
is
the
initial
velocity.
Let
(˜
y,
˜
p
)
be
a
fixed
solution
of
the
stationary
system
of
(1).
We
established
the
following
controllability
result:
in
certain
hypotheses,
there
exists
u
∈
L
2
(0
,
T
;
(
H
1
2
(
∂
Ω))
2
)
such
that
the
solution
of
the
system
(1)
satisfies
y
(
x,
T
)
=
˜
y
,
a.e.
in
Ω.
For
the
proof,
we
reduce
this
boundary
controllability
problem
to
a
local
exact
internal
controllability
problem
for
the
Navier-Stokes
system
with
Navier
boundary
conditions
and
then
we
apply
a
previous
result
we
have
obtained.
•
Aurelian
ISAR
,
Institute
of
Physics
and
Nuclear
Engineering,
Bucha-
rest-Magurele,
Full
Member
of
the
Academy
of
Romanian
Scientists;
email
address:
isar@theory.nipne.ro
Title:
Quantum
Entanglement
in
Curved
Spacetime
Abstract
:
The
influence
of
Hawking
radiation
on
quantum
entangle-
ment
for
bimodal
Gaussian
states
near
a
Schwarzschild
black
hole
is
inves-
tigated.
It
is
shown
that
for
a
thermal
squeezed
state
of
a
bimodal
bosonic
system
the
Hawking
radiation
reduces
and
even
can
destroy
the
entangle-
ment
between
the
mode
of
a
Kruskal
observer
and
the
mode
of
an
accelerated
observer
hovering
outside
the
event
horizon
of
black
hole.
We
investigate
also
the
influence
of
the
thermal
environment
on
the
behavior
in
time
of
the
entanglement
between
the
modes
of
the
two
considered
observers
and
show
that
the
entanglement
is
destroyed
in
a
finite
time
for
non-zero
values
of
the
temperature
of
the
thermal
environment,
i.e.,
the
so-called
phenomenon
of
entanglement
sudden
death
takes
place.
•
Gheorghe
MOROS
¸ANU
,
Babe¸
s-Bolyai
University,
Cluj-Napoca,
Romania,
Full
Member
of
the
Academy
of
Romanian
Scientists,
and
Lihe
WANG
,
University
of
Iowa,
Iowa
City,
IA,
USA
G.
Moro¸
sanu,
S.
Treant
¸˘
a
245
Title:
Bounded
Solutions
on
the
Positive
Semiaxis
for
an
In-
complete
Cauchy
Problem
Abstract
:
Consider
in
a
real
Hilbert
space
H
the
following
incomplete
Cauchy
problem
(
ICP
)
u

(
t
)
=
∇
φ
(
u
(
t
))
,
t
≥
0;
u
(0)
=
u
0
,
where
u
0
∈
H
is
a
given
vector,
and
φ
:
H
→
R
is
a
C
1
function,
whose
gradient
∇
φ
is
a
locally
Lipschitz
operator.
We
call
(
ICP
)
an
incomplete
Cauchy
problem
because
the
usual
addi-
tional
Cauchy
condition
u
(0)
=
v
0
is
missing.
The
differential
equation
above
is
important
because
it
expresses
the
law
of
conservation
of
energy
(this
becomes
obvious
after
scalar
multiplication
of
the
equation
by
u
(
t
)
and
integration
of
the
resulting
equation
on
the
interval
[0
,
t
]).
It
is
well
known
that
if
φ
is
a
convex
function,
possessing
at
least
one
minimum
point,
then
problem
(
ICP
)
has
a
unique
solution
bounded
on
the
positive
semiaxis
for
each
u
0
∈
H
.
Here
we
are
concerned
with
the
case
when
φ
is
not
convex,
and
in
par-
ticular
we
pay
attention
to
the
special
case
when
φ
is
quasi-convex
(i.e.,
its
level
sets
are
convex).
•
Adrian
PETRUS
¸EL
,
Babe¸
s-Bolyai
University,
Cluj-Napoca
and
Academy
of
Romanian
Scientists
Title:
Fibre
Contraction
Principle:
Theory
and
Applications
Abstract
:
We
will
focus
on
the
so-called
Fibre
Contraction
Principle,
both
for
single-valued
and
multi-valued
operators.
We
will
start
with
the
single-valued
case
and
some
applications
of
this
principle.
Then,
based
on
the
main
metric
fixed
point
theorem
for
multi
valued
contractions,
we
will
present
a
Multivalued
Fibre
Contraction
Principle
for
multi-valued
opera-
tors
with
applications
(based
on
some
joint
works
with
I.A.
Rus
and
M.A.
S
¸erban).
•
Dan
TIBA
,
Institute
of
Mathematics
Simion
Stoilow
of
the
Romanian
Academy,
Full
Member
of
the
Academy
of
Romanian
Scientists
Title:
Two
Superposed
Optimal
Design
Problems
with
Point-
wise
Boundary
Observation
RISMA
Spring
Session,
29
May
2026,
Bucharest,
Romania
246
Abstract
:
This
paper
is
devoted
to
some
geometric
optimization
prob-
lems
related
to
the
advantageous
placement
of
certain
utilities.
The
consid-
ered
performance
indices
include
naturally
pointwise
boundary
observation
terms.
Our
approach
is
based
on
the
use
of
Hamiltonian
systems
and
the
considered
optimization
problems
examine
the
questions
from
two
points
of
view:
the
optimal
distribution
of
the
sensors
in
a
given
geometric
setting,
respectively
the
optimal
design
of
a
geometric
structure
such
that
the
as-
sociated
optimized
pointwise
boundary
sensors
ensure
efficient
observation
characteristics.
The
subject
enters
the
optimal
design
theory
and
the
used
methodology
is
grounded
on
optimal
control
approaches.
Several
numerical
examples
are
also
included.
•
Savin
TREANT
¸
˘
A
,
National
University
of
Science
and
Technology
POLITEHNICA
Bucharest
&
Associate
Member
of
the
Academy
of
Roma-
nian
Scientists,
Bucharest
Title:
Optimality
and
Duality
Criteria
in
Constrained
Varia-
tional
Control
Models
Governed
by
Caputo
and
Riemann-Liouville
Fractional
Derivatives
Abstract
:
In
this
paper,
under
various
generalized
convexity
assump-
tions,
we
investigate
optimality
and
duality
criteria
associated
with
a
class
of
constrained
variational
control
models
governed
by
Caputo
and
Riemann-
Liouville
fractional
derivatives.
Concretely,
first,
we
define
the
concepts
of
controlled
invex
(pseudo-invex,
quasi-invex)
functionals
by
using
the
Caputo
fractional
derivative
of
order
0
<
α
≤
1.
Thereafter,
we
introduce
the
prob-
lem
under
study
by
considering
continuously
differentiable
interval-valued
functions.
In
order
to
analyze
its
solution
set,
we
establish
an
integration-by-
parts
formula
generating
the
Karush-Kuhn-Tucker
necessary
optimality
con-
ditions.
The
main
results
formulate
sufficient
optimality
criteria
for
the
con-
sidered
problem
under
invexity
(pseudo-invexity,
quasi-invexity)
hypotheses
of
the
involved
functionals.
Also,
we
continue
the
study
with
various
duality
results.