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Laurell, Pontus Bengt Johan
dmrgpp
Commits
729b945d
Commit
729b945d
authored
Dec 17, 2018
by
Alvarez, Gonzalo
Browse files
doc updated: operator expressions
parent
27313e49
Changes
1
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doc/manual.ptex
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729b945d
...
...
@@ 206,13 +206,14 @@ have a whatToMeasure argument as follows.
Braket
specifications
come
in
two
forms
:
bare
and
dressed
.
\
section
{
Bare
braket
specification
}
A
bare
braket
specification
is
a
semicolon

separated
list
of
at
least
one
opspecs
:
\
verb
!braket spec=opspec; opspec; opspec; ...!
If
just
one
opspec
is
given
(
no
semicolon
),
then
the
bare
braket
is
referred
to
as
A
bare
braket
specification
is
a
semicolon

separated
list
of
at
least
one
operator
expressions
(
opExpr
)
\
verb
!braket spec=opExpr; opExpr; opExpr; ...!
If
just
one
opExpr
is
given
(
no
semicolon
),
then
the
bare
braket
is
referred
to
as
``
local
''
or
one

point
;
if
two
op
specs
are
given
(
one
semicolon
),
then
the
bare
braket
is
refererred
to
as
a
if
two
op
Expr
are
given
(
one
semicolon
),
then
the
bare
braket
is
refererred
to
as
a
two

point
correlation
;
and
so
on
.
Bare
brakets
cannot
be
computed
directly
by
DMRG
++,
but
must
instead
be
Bare
brakets
cannot
be
computed
directly
by
DMRG
++,
but
must
first
be
dressed
with
a
bra
and
a
ket
.
What
bra
and
ket
is
chosen
is
Targeting
and
context
dependent
.
For
GroundStateTargeting
,
bra
and
ket
are
both
equal
to
the
current
target
,
usually
the
ground
state
,
...
...
@@ 238,7 +239,51 @@ where bra is the GroundStateTargeting vector, and
ket
the
first
time
vector
.
The
same
is
true
for
CorrectionVectorTargeting
,
where
ket
is
the
correction
vector
.
\
section
{
Operator
Expressions
}
{\
textsc
An
operator
expression
}
is
an
algebraic
expression
involving
floating
point
numbers
and
operator
specifications
or
\
texttt
{
opSpec
}
s
.
For
example
,
\
begin
{
verbatim
}
3
*
nup
+
ndown
*(
1.5
*:
sz
.
txt

3.5
*(
c
?
1
'*c?1 + I)).
\end{verbatim}
A \emph{canonical operator expression} is an operator expression composed of one or
more canonical operator terms separated by the plus $+$ sign.
A \emph{canonical operator term} is a string that starts with an
optional canonical scalar,
followed by a star $*$, followed by one or more \texttt{opSpec}s concatenated
by starts $*$.
A canonical scalar is of one the following
forms.
\begin{enumerate}
\item One or more digits, followed by an optional dot $.$, followed by zero or
more digits. For example, $3.5$, $3.$, $3$.
\item A dot $.$ followed by one or more digits. For example, $.5$.
\item A parenthesis followed by an optional minus sign $$,
followed by a scalar prefix of form (1) or (2) above, and ending in a
parenthesis.
For example, $(3.5)$ $(3)$ $(.5)$ $(.5)$ $(3.)$ $(3.)$.
\end{enumerate}
Note that these scalars are \emph{not} canonical: $+3.5$, $(+3.5)$, $3.5$.
The sample expression above in canonical form is
\begin{verbatim}
3*nup + 1.5*ndown*:sz.txt + (3.5)*ndown*c?1'
*
c
?
1
+
3.5
*
ndown
*
I
.
\
end
{
verbatim
}
\
textsc
{
A
}
\
texttt
{
opExpr
}
can
be
used
in
the
following
cases
.
(
1
)
In
a
bare
braket
spec
:
\
texttt
{
braketSpec
=
opExpr
;
opExpr
;...}
(
2
)
In
a
dressed
braket
spec
:
\
texttt
{
braketSpec
=}
\
texttt
{<
bra

opExpr
;
opExpr
;...
ket
>}.
(
3
)
After
the
input
label
\
texttt
{
OperatorExpression
=}
when
\
texttt
{
TSPOperator
=
expression
}
is
specified
.
And
(
4
)
after
the
option
\
verb
!e! in the operator driver.
\
emph
{
Only
canonical
operator
expression
have
been
implemented
so
far
.}
\
section
{
Operator
specifications
}
There
are
two
kinds
of
operator
specifications
:
by
label
and
by
file
.
By
label
,
it
is
given
by
\
verb
!name[site]?dof'!
...
...
@@ 272,7 +317,7 @@ following items, in order.
\
end
{
itemize
}
\
section
{
Dressed
braket
specification
}
Note
:
This
is
an
experimental
feature
.
Operators
in
braket
specifications
may
be
dressed
,
as
follows
.
\
begin
{
verbatim
}
./
dmrg

f
input
.
inp
'<brabare braketket>,<brabare braketket>,...'
...
...
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