Bilge wrote:
Basically, the only real ``failure'' of quantum field
theory is that experimentalists have failed to find any new phenomena that
would keep the theorists busy creating quantum field theories as
explanations,.

Ah, but there are reasonably good indications that something new may
happen just above the electro-weak scale of a few hundred GeV. And the
neat thing is this regime is accessible to the LHC, which will be
starting up next year.


Tom Roberts

Bilge wrote:
snip

At the moment, quantum field theory has no failings. At least not any real
ones, if by ``failings'' one means failing to predict the phenomena it
purports to describe. (Seriously - it predicts phenomena that no longer
occur anywhere in the universe other than the accelerator labs needed to
test the theory.) Basically, the only real ``failure'' of quantum field
theory is that experimentalists have failed to find any new phenomena that
would keep the theorists busy creating quantum field theories as
explanations,. One might consider this general lull in the experimental
action to indicate just how much quantum field theory has not failed.
Working better than anyone could have expected is usually a plus.

This is not to say that quantum field theory is perfect or even too good
to consider alternatives to replace it, but as imperfect and possibly wrong
theories go, it beats everything before it, or even on the horizon, hands
down.

That's quite a claim. Can QFT predict fracture?
--
Andrew Resnick, Ph.D.
Department of Physiology and Biophysics
Case Western Reserve University

On 2007-06-22, Andy Resnick wrote:
Bilge wrote:
snip

At the moment, quantum field theory has no failings. At least not any real
ones, if by ``failings'' one means failing to predict the phenomena it
purports to describe. (Seriously - it predicts phenomena that no longer
occur anywhere in the universe other than the accelerator labs needed to
test the theory.) Basically, the only real ``failure'' of quantum field
theory is that experimentalists have failed to find any new phenomena that
would keep the theorists busy creating quantum field theories as
explanations,. One might consider this general lull in the experimental
action to indicate just how much quantum field theory has not failed.
Working better than anyone could have expected is usually a plus.

This is not to say that quantum field theory is perfect or even too good
to consider alternatives to replace it, but as imperfect and possibly wrong
theories go, it beats everything before it, or even on the horizon, hands
down.

That's quite a claim. Can QFT predict fracture?

Fracture? I think you have misconstrued my point, since right
off-hand, you seem to be referring to some phenomenological model
which is phenomenological precisely because a calculation from
first principles would be intractable. However, let me put it another
way. Are you referring to some process that doesn't involve electro-
magnetic, weak or strong interactions? If not, do you know of any theory
of ``fracture'' which can be better obtained from some other fundamental
theory of the forces involved?

Bilge wrote:

On 2007-06-22, Andy Resnick wrote:

Bilge wrote:
snip

At the moment, quantum field theory has no failings. At least not any real
ones, if by ``failings'' one means failing to predict the phenomena it
purports to describe. (Seriously - it predicts phenomena that no longer
occur anywhere in the universe other than the accelerator labs needed to
test the theory.) Basically, the only real ``failure'' of quantum field
theory is that experimentalists have failed to find any new phenomena that
would keep the theorists busy creating quantum field theories as
explanations,. One might consider this general lull in the experimental
action to indicate just how much quantum field theory has not failed.
Working better than anyone could have expected is usually a plus.

This is not to say that quantum field theory is perfect or even too good
to consider alternatives to replace it, but as imperfect and possibly wrong
theories go, it beats everything before it, or even on the horizon, hands
down.

That's quite a claim. Can QFT predict fracture?


Fracture? I think you have misconstrued my point, since right
off-hand, you seem to be referring to some phenomenological model
which is phenomenological precisely because a calculation from
first principles would be intractable. However, let me put it another
way. Are you referring to some process that doesn't involve electro-
magnetic, weak or strong interactions? If not, do you know of any theory
of ``fracture'' which can be better obtained from some other fundamental
theory of the forces involved?

Again, I understand what you are saying, but you should be more careful
when making statements like "Basically, the only real ``failure'' of
quantum field theory is that experimentalists have failed to find any
new phenomena that would keep the theorists busy creating quantum field
theories as explanations.", since there are many commonly occuring
phenomena that cannot be generated from first-principles application of
QFT.

I could counter by stating "Basically, the only real "failure" of
quantum field theory is that the calculations rapidly become too complex
for treating any meso- or macroscopical physical system, and theorists
appear uninterested in applying QFT to, for example, the glassy state of
matter. Even so, there is a persistent claim by people who should know
better that QFT is capable of predicting and describing all features of
reality, a claim that must clearly be labeled *unsubstantiated*"

--
Andrew Resnick, Ph.D.
Department of Physiology and Biophysics
Case Western Reserve University

On Jun 16, 6:24 pm, Eric Gisse wrote:
http://www.amazon.com/Quantum-Field-...duction/dp/019...

I yoinked it from the library and have been learning a bit from it
since. My understanding of group theory has improved a fair bit.

It seems suited for my level of understanding, but I'm wondering if
any of you have any differing opinions / book counter-suggestions.

Since my heart is set on understanding gravity, I figure teaching
myself a chunk of quantum field theory would be a useful step. I need
to understand where both theories fail in order to understand how to
make them work - I hate taking for granted what I'm told about QFT's
failings.

eric

i know this is an old thread
and you may have moved on since
but i just wanted to mention that kaku's book is pretty mediocre

i certainly wouldn't expect much teaching to arise from it

the problem is
this was meant as a book only for his credentials
which he then sold to the highest bidder
( apparently discovery channel )

he threw in everything he could
which means he tried to touch on all the active areas
even remotely related to the core of qft
and you can tell that from the exposition

there is no conceptual cohesion

there are no threads of discourse

its exercises do not follow the text well
and require much development outside what is covered
indicating he probably had some students lifting them from others

the fact that he made no substantial contributions to the field
is understandable from his often confused exposition

at best
it is a reference book for those who have studied elsewhere
but there are even better in this regard

i would certainly recommend zee and others over kaku

-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
galathaea: prankster, fablist, magician, liar

On 2007-07-02, Andy Resnick wrote:
Bilge wrote:

way. Are you referring to some process that doesn't involve electro-
magnetic, weak or strong interactions? If not, do you know of any theory
of ``fracture'' which can be better obtained from some other fundamental
theory of the forces involved?

Again, I understand what you are saying, but you should be more careful
when making statements like "Basically, the only real ``failure'' of
quantum field theory is that experimentalists have failed to find any
new phenomena that would keep the theorists busy creating quantum field
theories as explanations.", since there are many commonly occuring
phenomena that cannot be generated from first-principles application of
QFT.

Sure, but something appears to have gotten lost in the translation,
since I can't figure out how your replies relate to anything that
comment was intended to convey. I only intended to point out the irony
in having so much time to lament over hypothetical ``failures'' in
quantum field theories because the theories have been so successful.

For example, do you know anyone who seriously thought that the
eventual discovery of the t-quark and \tau neutrino was a cliff hanger
after 1983? How about after 1977? (which was when the b-quark was
discoverd, but before my time) I would personally be very happy to
publish a theory which has a great many more failures, if it was
half as successful.

I could counter by stating "Basically, the only real "failure" of
quantum field theory is that the calculations rapidly become too complex
for treating any meso- or macroscopical physical system, and theorists
appear uninterested in applying QFT to, for example, the glassy state of
matter.

You could say that, but I'm not sure why or what it counters.

Even so, there is a persistent claim by people who should know
better that QFT is capable of predicting and describing all features of
reality, a claim that must clearly be labeled *unsubstantiated*"

However, I did not make that claim. I only claimed that quantum
field theories are the best description of reality available at
the moment.

Bilge wrote:
On 2007-07-02, Andy Resnick wrote:

snip


Even so, there is a persistent claim by people who should know
better that QFT is capable of predicting and describing all features of
reality, a claim that must clearly be labeled *unsubstantiated*"


However, I did not make that claim. I only claimed that quantum
field theories are the best description of reality available at
the moment.

Fair enough. I still claim that classical continuum mechanics is the
most useful and widely-applied description of reality.

--
Andrew Resnick, Ph.D.
Department of Physiology and Biophysics
Case Western Reserve University