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Ciro Santilli
@cirosantilli
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Expectation value
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Body
0
Momentum operator
Updated
2025-04-24
+
Created
1970-01-01
View more
One
dimension
in
position representation
:
p
^
=
−
i
ℏ
∂
x
∂
(1)
In three
dimensions
In
position representation
,
we
define
it by using the
gradient
, and so
we
see that
p
^
=
−
i
ℏ
∂
x
∂
(2)
Video 1.
Position
and
Momentum
from Wavefunctions by
Faculty of Khan
(2018)
Source
. Proves in detail why the
momentum operator
is
∂
x
∂
. The starting point is determining the
time
derivative
of the
expectation value
of the
position operator
.
0
Solution of the Ising model
Updated
2025-04-24
+
Created
1970-01-01
View more
TODO
what it
means
to solve an
Ising model
in general?
stanford.edu/~jeffjar/statmech/lec4.html
gives some
good
notions:
<
σ
i
>
is the
expectation value
of the value. It is therefore
a
number
between -
1
.
0
an and
1
.
0
, -
1
.
0
means
everything
is always down,
0
.
0
means
half up half down, and
1
.
0
means
all up
<
σ
i
σ
j
>
:
correlation
between neighboring states.
TODO
.
Total
articles
:
2