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Answer of the Most Important Unsettled Question of Physical
Theory in 20th Century—Can Schrödinger Equation Describe
Transition Processes
Junhoa Zhang Shantou University Shantou People’s Republic of
China
Abstract
Quantum mechanics take the sum of first finite order
approximate solutions of time-dependent perturbation to substitute the exact
solution, it will produce the error. How much is this error? However people do
not find up
for arbitrary N and the exact solution
, so quantum mechanics can not answer this question. Therefore this
‘unknown error’ is as a premise of all theoretical conclusions of quantum
mechanics for the transition processes. This problem is relative to the
question. Can we really use the Schrödinger equation to describe the
transition processes? So it is the most important unsettling problem of physical
theory in 20th century. All of physical theory cannot avoid the
strictly mathematical inference.
We find out the time-dependent perturbation approximate
solution
for arbitrary
order and the exact solution .
Then we can prove that: (1) In the neighborhood of energy conservation, the
series is divergent. The basic error of quantum mechanics is using the sum of
the first finite order approximate solutions to substitute the exact solution in
this divergent region. It leads to an infinite error. So the Fermi’s golden
rule is not a mathematically reasonable inference of the Schrödinger
equation (2) The transition probability per unit time deduced from the exact
solution of Schrödinger equation cannot describe the
transition processes.
(1) The most important unsettled question of physical theory
in 20th century
Quantum mechanics deems that, we can use the Schrödinger
equation
(1)
to describe the variance of the system with time, where
(2)
We may write the
as the product of time independent
with a time dependent factor .
Quantum mechanics only discusses two types ,
they are
(3)
and
(4)
The eigenvalues of
are discrete or continuous. We shall discuss for each case. In discrete case,
according to quantum mechanics, suppose
(5)
Then the Schrödinger equation may be written as
(6)
The time-dependent perturbation theory supposes that
(7)
and uses the approximate equations
(8)
(9)
to substitute the exact equation (6).
So far, people only find the few order approximate solutions
of (7). We do not find out
for arbitrary
order. The only way is to substitute the exact solution by the sum of first
finite order approximate solutions
(10)
and to use this sum to describe the transition processes.
The problem is that, whether the
may be abandoned? From the point of physics, if the abandoned part is large then
the experimental error, then we cannot obtain any conclusion from the comparison
between the sum of first finite order approximate solutions with experimental
results. In this case, the words “Schrödinger
equation may describe the transition processes” would be meaningless. From the
point of mathematics,
is the function of energy .
Only in the convergent range of series, for ,
we can find a number M , that the relation
(11)
is satisfied. What is
for arbitrary
order? What is the exact solution ?
In which range is the series divergent? These questions are relative to that,
can the equation of quantum mechanics describe the transition processes? So it
is the most important unsettled question of physical theory.
(2) Discussion in the case in which the eigenvalues of are
discrete and the time factor is 
The equations (6) and (9) contain ,
it means that we discuss in the discrete case. We shall solve the Schrödinger
equation and its approximate equations in the range .
(2-1) Expression of
for arbitrary
Quantum mechanics found out the first finite order time
dependent perturbation approximate solutions. The forms of first and second
order approximate solutions are simple. However it is difficult to look for the
general form of the approximate solution from them. The purpose of this section
is to find the another form of the approximate solution, it can help us to seek
the general form of the high order approximate solution.
Considering the stationary state equation
(12)
(13)
Let us use the stationary state perturbation solution
(14)
(15)
to substitute
in the expression of ,
then it is easy to discover the general form of the time dependent perturbation
approximate solution.
and
satisfies the stationary state approximate equations
(16)
(17)
where satisfies
the orthonormalization condition

(18)
In appendix A we prove that the
order time dependent perturbation approximate solutions may be expressed as
(19)
(20)
(21)
The first order of time dependent perturbation approximate
solution deduced by quantum mechanics does not contain the
term. This term is
(22)
It is just the term
in Eq. (20). So you see the result give by quantum mechanics is incomplete. The
incompleteness in the low order approximate solution will influence the
calculation in the high order approximate solution.
According to Eqs.(19) —(21), you may easy to discover that
the general form for arbitrary N order time dependent perturbation approximate
solution is
(23)
where the coefficients are
(24)
(25)
(26)
We shall take
in the latter calculation, so we have
(27)
According to Eqs.(24)—(26), you may guess that the general
form of must
be
(28)
Because the first order time dependent perturbation
approximate solution deduced by quantum mechanics is incomplete, then the high
order approximate solution will do not contain the term relative to .
For comparing, let us consider the first term of Eq.(23),
(29)
This formula contains all of orders approximate solution
deduced by quantum mechanics. For example, in the case of ,
we obtain
 (30)
from Eq.(29). The second order approximate solution deduced
by quantum mechanics is
(31)
The difference between these two equations is due to that
quantum mechanics neglects the contribution of
in calculation the first order approximate solution. The simple formula of Eq.(29)
not only contain all order approximate solutions that they have been found out.
It is also correct in the case for arbitrary
order.
Other coefficients
are
(32)
(33)
(34)
The general form is
(35)
where is
the function of ,
it is not relative to .The
recurrence relation is
(36)
(37)
 is
the sum of many terms, each term contains
factors of
(38)
The total of approximate order
is
(39)
Summarizing above results, the expression of
for arbitrary
order
is

We prove this formula in the case ,
but it is only a guess in the high order case. However the task focus on the
proposition, if Eq.(40) is correct for
order, try to prove that it is correct for
order. We prove this proposition in appendix B.
(2-2) The expression of the exact solution
According to Eq.(7), the exact solution is

Calculating this expression, we may obtain
(42)
You can find the calculating process in appendix C. The
opposite process is to expand
presented in Eq.(42) by using the stationary-state perturbation approximation,
we may obtain the different order of time-dependent perturbation approximate
solution .
Finally we test that
is the exact solution of the Schrödinger equation in
appendix D. It means that this conclusion is correct not only in the convergent
intervals, but also correct in the divergent intervals of the series.
(2-3) The error of time-dependent perturbation approximation
Now we affirm three points:
(i) Eq.(42) is satisfied the Schrödinger
equation and the special initial condition;
(ii) Expanding the coefficient
presented in
according to the stationary
state perturbation, and classifying according to the different
approximate order we get
;
(iii)
is satisfied the time-dependent perturbation approximate equation and special
initial condition.
They are the basic to discuss the core of unsettled
question—in which range is the series divergent?
The exact solution
must be expressed by the solution of stationary state equation .
Substituting the stationary state perturbation approximate solution into
presented in the exact solution, we shall obtain the different order
approximations of the time–dependent perturbation method .
Therefore, the divergent intervals of the time-dependent perturbation approach
and the one of the stationary state perturbation approach are identical.
Quantum mechanics pointed out that the divergent interval of the stationary
state perturbation series is .
So it must be the divergent interval of the time-dependent perturbation
series. It means that, for each ,
no matter how much
order approach solutions we take into account, the relation

does not satisfy in the divergent interval. We cannot use the
sum of first finite order of time-dependent perturbation solutions to substitute
the exact solution. The error of time-dependent perturbation method is using
to substitute
for calculating the transition probability in the divergent range .
Let us examine the first-order approximation of the
time-dependent perturbation

 is the -component
of an unit vector. Therefore
(44)
and Eq.(43) can only be used in the region .
According to quantum mechanics, we have
(45)
(46)
There are two questions. First, the premise of this section
is that we discuss in the discrete case. Quantum mechanics changes to discuss
the continuous case and simply substitutes Eq.(45) with Eq.(46). Is this
reasonable? We shall discuss this question in the next section. Second, the
transition probability deduced from the perturbation approximation is correct
only in the region ;
the fault is in .
If we use the expression of the first order stationary state perturbed approach
in the region ,
the error is
If .
Quantum mechanics discuss the relation between
with .
And pointed out there is a peak of function in ,
this peak of function is just deduced from the error factor .
If ,
the high of peak tends to infinite,and the breadth of the peak tends to zero, the discussed
function becomes
function. However if
 , the whole
main peak of
function is in the divergent region of the perturbation approximate series. The
problem is that it is under these two conditions, ,
and

Fig.1 The relation between
with ,
where I is the
divergent region of the time-dependent perturbation
approximate series.
 , that quantum
mechanics obtains
(47)
from Eq.(46). Fermi called it as the golden rule. Of course,
if this formula is correct, then someone can find a suitable
to be identical with the experimental value ,
but mathematically Fermi’s golden rule is not a reasonable conclusion from the
Schrödinger equation.
(2-4) Transition probability per unit time deduced from the
exact solution
According to quantum mechanics, the transition probability
per unit time is defined as
(48)
Note that
(49)
It means that
is the -component
of a unit vector, and
is the -component
of another unit vector. The expression

is the product of two unit vectors, so
(50)
Finally we obtain
(51)
This is the result deduced from the exact solution of Schrödinger
equation (1) in the
case. This result cannot be used to describe the transition
processes.
We summarize the discussion in the discrete case:
- The substance of the time-dependent perturbation approximation is to
expand
presenting the expression of
according to the stationary-state perturbation approach..
The convergent interval of the stationary-state perturbation approach is ,
this region is also the convergent interval of the time-dependent perturbation
approach..
The sum of the first finite order perturbation approximate solutions may
be used to substitute the exact solution only in the convergent interval.
The fundamental error of the time-dependent perturbation approach is using
the sum of the first finite order approximate solutions to calculate the
transition probability in the divergent interval .
Mathematically Fermi’s golden rule is not a reasonable conclusion from the
Schrödinger equation in the discrete case.
People use the sum of first finite order perturbation approximate
solutions to substitute the exact solution. It only caused by that they did
not find out the approximate solution
for arbitrary order.
When we find out
and , then we have not any reason to use the sum of first
finite order perturbation approximate solutions to substitute the exact
solution. The pity is that, the transition probability per unit time deduced
from the exact solution of the Schrödinger equation is zero in the discrete
case, it cannot be used to describe the transition processes.
(3) Discussion in the case in which the eigenvalues of are
continuous and the time factor is 
In the continuous case, the discrete variable
must change to continuous variable ,
the summation must change to the integration, and
presented in the discrete case must change to ,
the others are same as in the discrete case. This kind of variation cannot give
the difference result.
(3-1) Exact solution
In the continuous case the Schrödinger
equation has the form
(52)
The initial condition can be expressed in the form
(53)
If the initial condition takes the form of Eq.(53), then at
the probability of the system in the region
is
(54)
We can prove that the exact solution of the Schrödinger
equation (52) in the special initial condition is
(55)
where
are the eigenvalue and eigenfunction of the stationary-state equation
(56)
respectively.
At the same time, the eigenfunctions satisfy the
orthonormalization conditions
(57)
(58)
(3-2) Equivalence of the time-dependent perturbation
approximation and the stationary-state perturbation approximation
According to the stationary-state perturbation approximation
method, suppose that
,
(59)
where
satisfy a set of equations
(60)
and satisfy the orthonormalization condition
(61)
(62)
Inserting the stationary-state perturbation approach Eq.(59)
into Eq.(55), and decomposing them according to the approximate order, we obtain
(63)
where

The relations between
with
are same as in the discrete case.
are the solution of the time-dependent perturbation approximate equations
(65)
The approximate solutions satisfy the initial conditions
(66)
(67)
The time-dependent perturbation approximation is equivalent
to the stationary-state perturbation approximation in this case.
(3-3) Error of deduction of transition probability from the
time-dependent perturbation approach
The zeroth and first-order stationary-state perturbation
approximations are
,
(68)
Even if we can use the first order time-dependent
perturbation approximation, in the continuous case the correct expression of the
first order approximation must be
(69)
However, at ,
the probability of the system in is .
Then the relative transition probability per unit time is
(70)
It cannot describe the transition processes.
(3-4) Deduction of the transition probability from the exact
solution
The transition probability in
is a relative probability. It is defined as
(71)
In this equation the denominator is
 (72)
the numerator is
(73)
In the continuous case,
satisfies the orthonormalization condition (57). Then
is the -component
of a normalization vector, and
is the -component
of another normalization vector. The expression

is the product of two normalization vectors, so
(74)
The transition probability per unit time is
(75)
In the continuous case the transition probability per unit
time deduced from the exact solution of the Schrödinger equation is still
zero.
(4) Discussion in the case in which the time factor is
and the eigenvalues of are
discrete
Quantum mechanics uses
(76)
to describe the electron transition from one energy level to
another due to the impact of the electromagnetic field. In general, only the
discrete is discussed. The Schrödinger
equation has the form
where
(78)
Suppose
(79)
where is
the probability amplitude of the state in which there is an electron in
and
photons of energy .
If at ,
the system is in the state
then
(80)
According to Eq.(77) and Eq.(80), we get
(81)
which ,
are the solution of the stationary-state equation
(82)
Suppose
(83)
then Eq.(82) may be rewritten in the form
(84)
At the same time, meets
the orthonormalization conditions of the eigenfunctions:
(85)
(86)
Obviously, the exact solutions solved under the cases
and
have the identical mathematical structure. The results in Sec. 2 are still
applicable in this case.
Conclusion
- In the cases in which the time factors are
or ,
the eigenvalues of
are discrete or continuous, the process to deduce the transition probability per
unit time from time-dependent perturbation approximation contains a basic
mathematical mistake. It is using the sum of first finite order approximate
solutions to substitute the exact solution for calculating the transition
probability in the divergent range—the neighborhood of energy conservation.
Fermi’s golden rule is not the mathematically reasonable deductive inference
from the Schrödinger equation.
The transition probability per unit time deduced from the exact solution of
the Schrödinger equation cannot be used to describe
time-dependent processes.
(5) Other equations in quantum mechanics
There are other equations in quantum mechanics, such as the
unitary matrix equation
(87)
and the Dyson’s equation (method of Green’s function)
(88)
The unitary matrix equation is suited to extend to
quantization of field. We have discussed these two equations. The result is same
as the Schrödinger equation. The exact solution cannot be used to describe
the time dependent processes.
The basic task of quantum mechanics is to describe the
stationary motion of the system and the time dependent processes. If the exact
solution cannot be used to describe the time dependent processes, then we must
reconsider the basic point and the basic picture of quantum mechanics.
Appendix A: Deducing of first finite orders time dependent
perturbation approximate solutions
Quantum mechanics found out the first finite order time
dependent perturbation solutions, but it is difficult to look for the general
form of the high order solution from them. We introduce a new method to
calculate the approximate solution and obtain a new expression. It is more
complex then the usual way, but you can easy to look for the general form of
arbitrary
order approximate solution from them.
We shall use the stationary state perturbation equations
(A1)
(A2)
(A3)
The normalization conditions of eigenfunctions are
(A4)
(A5)
(A6)
According to Eqs.(A1) and (A4), we get
 (A7)
The zeroth order time dependent perturbation approximate
equation is
(A8)
and the special initial condition is
(A9)
According to these two equations we obtain
(A10)
where
(A11)
Using this form is only for to expand the result to the high
order approximate solution. We always take
(A12)
in the latter calculation.
The first order time dependent perturbation approximate
equation is
(A13)
According to Eq. (A2), we obtain
(A14)
We add a term to the second line of this expression.
According to Eq. (A1), the contribution of this term is zero. We shall explain
it in latter. The definition of
is
(A15)
Then Eq.(A13) may be written as
(A16)
Suppose that has
the form
(A17)
Differentiating the Eq.(A17) we get
(A18)
Comparing Eq. (A16) with Eq. (A18), we obtain
(A19)
(A20)
So
(A21)
(A22)
The first order time dependent perturbation approximate
solution
deduced from quantum mechanics does not contain the term ,
this term is
(A23)
It is corresponding to the term
in Eq. (A17).
According to Eq.(A17),
(A24)
therefore satisfies
the special initial condition. It is the reason that we add a term in Eq.(A14).
The second order time dependent perturbation approximate
equation is
 (A25)
where
(A26)
We add a term
(A27)
in Eq. (A26). The definition of
is
(A28)
In addition we have

(A29)
Therefore we obtain
 (A30)
The right side of this expression is sum for all .
When ,
it has the form .
So the expression of contains
the term of .
So we suppose that the solution has the form
(A31)
Therefore

Comparing Eq.(A30) with Eq.(A32), we get
(A33)
(A34)
(A35)
Finally we find
(A36)
(A37)
(A38)
According to Eq. (A31)
(A39)
 satisfies the
initial condition.
Now we collect above results,
(A10)
(A17)
(A31)
The coefficients decompose
two sets, one set is ,
and another set is .
For the set ,
we have
(A11)
(A22)
(A36)
therefore we may image that
(A40)
where
(A41)
The another set is
(A21)
(A38)
(A37)
Then we may image that, in the case
(A42)
where is
only the function of .
The first few
functions are
(A43)
(A44)
(A45)
We shall obtain more knowledge of
in
the latter,
(A46)
(A47)
 is the sum of
many terms, each term contains
factors of ,
The sum of approximate order is
(A48)
Appendix B: The time-dependent perturbation approximate
solution
is Eq.(40) for arbitrary N order
Now let us prove that the time-dependent perturbation
approximate solution is

by the substitutive method, where
(B1)
(B2)
(B3)
(B4)
Firstly, we prove a preparative formula
(B5)
The stationary state equation is
(B6)
Its perturbation approximate equations are
(B7)
(B8)
So we get
(B9)
We obtain that
the first term of (B9) (B10)
because of
(B11)
The second term of (B9) is relative to . The region of two sums is in
Fig.2.
Fig. 2 The region of two sums is on the triangle (containing the boundary).
We may exchange two sums by this way

and obtain that
the second term of (B9) (B12)
Then the relation
(B5)
is correct.
Now we use the inductive method to prove the time-dependent perturbation approximate solution
for arbitrary N order is
(40)
If , (40) may be simplified as
(B13)
It is the solution of zeroth order time-dependent perturbation equation and satisfies the special initial condition. If
, (40) may be simplified as
(B14)
It is the solution of the first order time-dependent perturbation equation and satisfies the initial condition.
Supposing that the solution of N order perturbation equation is (40), we shall prove that the solution of N+1 order perturbation equation has the form same as (40).

(B15)
The first term of (B15) =

A factor in second term of (B15) is
Fig.3 Exchanging two sums in above expression, .
Where
(B16)
Therefore,
the second term of (B15)

Substituting above results into (B15), we get
(B17)
Now let us prove that the expression of
is
(B18)
In fact,
(B19)
So (B17) satisfies the N+1 order perturbation approximate equation. In addition,
(B20)
Therefore satisfies the special initial condition. So we prove that, if (40) is correct for N order, then it must be correct for (N+1) order. We have prove this expression is correct for N=0,1orders. So it must be correct for arbitrary N order.
Appendix C: The expression of exact solution
We have obtain
(C1)
Fig. 4 Exchanging two sums in Eq.(C1), .
According to the time-dependent perturbation approximate method, the exact solution is defined as
(C2)
Now the task is to calculate the sum in this expression. Notice that the contribution of second term of Eq.(C2) in the case
is zero. Therefore
(C3)
Suppose
(C4)
then we have
(C5)
Using this relation, (C2) may be written as
(C6)

Fig.5 Exchanging two sums in Eq.(C6), .
We prove that the relation
(C7)
is correct.
According to (B2), we get
(C8)
so (C7) is correct for . Suppose that (C7) is correct for
, then we have
(C9)
Therefore (C7) is correct for . The conclusion is that the relation (C7) is correct for arbitrary
.
According to Eq.(B1),
(C10)
Substituting Eqs.(C7) and (C10) into Eq.(C6), we finally obtain
(C11)
It is just the exact solution of Schrödinger equation. From this deducing process, we conversely prove that, using the stationary state perturbation method to expand
in exact solution, we may obtain the different order of time-dependent solutions.
Appendix D: Test the exact solution of Schrödinger equation
Now we test that, is
(D1)
the exact solution of Schrödinger equation? Does it satisfy the initial condition? In fact,
(D2)
Therefore Eq.(D1) satisfies the Schrödinger equation. In addition, if 
(D3)
It is the special initial condition.
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Fig.3
Fig.4
Fig.5
References
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2. R.P. Feynman, Phys. Rev. 76,749 (1949).
3. Idem, Rev. Mod. Phys. 20, 367 (1948).
4. T.Y. Wu and T. Ohmura, The Quantum Theory of Scattering (Prentice Hall, Englewood Cliffs, NJ,1962).
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