HDTenEightyP/NetNews huggingface dataset:
From: guncer@enuxha.eas.asu.edu (Selim E. Guncer)
Newsgroups: sci.physics
Subject: Re: Hot Phonon effect?
Date: 16 Apr 92 20:29:40 GMT
Organization: Arizona State University

In article <1992Apr7.160355.2968@darwin.ntu.edu.au>, 910436a@darwin.ntu.edu.au writes:
> Hot Phonon effect
> 
> Could anybody out there explain what a hot phonon effect is...what are the 
> chracteristics of a hot phonon...higher frequencies?
> 
> Ms Thila
> NTU
> Australia


"Hot" in hot phonons doesn't mean their energies are higher.
It just means the population of phonons is higher than that
governed by thermal equilibrium with the lattice temperature. Normally,
the occupation probability of a phonon mode is given by a Bose
distribution:

    N = 1/(exp(hw/kT)-1)

When we have more phonons than N (which is per unit cell here)
given by lattice temperature T, it means the phonon temperature 
is higher than T.

I don't know much about hot phonons other than in semiconductor
transport.  When we have high electron-phonon scattering rates, the 
probability of phonon emission is proportional to (N+1) as opposed
to N for the probability of phonon absorption. Hence as carriers
encounter phonon scattering processes, the phonon population rises
above the thermal equilibrium population and becomes hot. The 
implication is that the scattering rates are now increased, and more
phonons are produced. This is important since energy loss rates are
increased, especially in high field (hot electron) low dimensional devices. 
This is termed as the "hot phonon bottleneck". 

Hope this helps. 

Selim Guncer



--
Selim Guncer	    Me viene, hay dias, una gana politica, de querer,
CSSER-ASU	     de basar al cari~no en sus dos rostros, y me viene  
(602)-965-4096	      de lejos un querer demonstrativo, otro querer amar, 
		       de grado o fuerza, al que me odia.. (Cesar V. )
From: sawyer@sscvx1.ssc.gov (Lee Sawyer)
Newsgroups: sci.physics
Subject: Re: "what's new" Apr-10-1992
Date: 14 Apr 92 18:56:00 GMT
Organization: Superconducting Super Collider Laboratory
News-Software: VAX/VMS VNEWS 1.4-b1

In article <92101.162358WTU@psuvm.psu.edu>, WTU@psuvm.psu.edu                  writes...
>=========================================================================
> 
>WHAT'S NEW, Friday, 10 April 1992                  Washington, DC
> 
>1. THE APS PLANS TO ASSIST PHYSICISTS IN THE FORMER SOVIET UNION!
>Ernest Henley, APS President, issued an appeal for donations to a
>special fund for FSU physicists. [deletions] Now they need our help.

 I know a lot of FSU physicists, in fact I earned my PhD there.
I know Gov. Chiles is cutting back the budget, but to my knowledge
there are no breadlines in Tallahassee.

 Seriously, isn't CIS the accepted abbreviation now ? "CIS and Baltic
States" would include everyone.

>Francis Slakey  OPA@AIP.bitnet      The American Physical Society
> 

 What happened to Robert Park ?

 ==============================================================================
         Lee Sawyer     | Dept of Physics          
       (SSCVX1::SAWYER) | Univ of Texas - Arlington    
                        | Arlington, TX            
 ==============================================================================
Xref: sparky sci.physics:6806 sci.skeptic:8130
From: haynes@cats.ucsc.edu (Jim Haynes)
Newsgroups: sci.physics,sci.skeptic
Subject: Re: Some quotes (Augustine on mathematics)
Date: 16 Apr 92 04:55:11 GMT
Followup-To: sci.physics
Organization: University of California, Santa Cruz



"The good Christian should beware of mathematicians and all those who make
empty prophecies.  The danger already exists that mathematicians have made
a covenant with the devil to darken the spirit and confine man in the bonds
of Hell"
	St. Augustine, quoted by Donald W. Robinson

-- 
haynes@cats.ucsc.edu
haynes@cats.bitnet

"Any clod can have the facts, but having opinions is an Art."
        Charles McCabe, San Francisco Chronicle

Xref: sparky sci.physics:6670 sci.electronics:8275
From: raju@bass.bu.edu (rajminder Singh)
Newsgroups: sci.physics,sci.electronics
Subject: Voltage drop in Silicon diode
Date: 10 Apr 92 03:24:57 GMT
Reply-To: raju@buengf.bu.edu (Rajminder Singh)
Followup-To: sci.physics
Organization: College of Engineering, Boston University, Boston, MA, USA

Hi there! I am  taking a course in Solid State Physics but I still 
haven't been able to answer the basic question of why the voltage drop
in a Silicon p-n junction is around 0.7 Volts ? Does this vary significantly
with the doping level ? What about the effect of temperature, current and
the energy band gap (E) of the material used in the junction ?

Thanks in advance for your help !

raju@buengf.bu.edu
raju@bass.bu.edu
From: DOCTORJ@SLACVM.SLAC.STANFORD.EDU (Jon J Thaler)
Newsgroups: sci.physics
Subject: Re: Xeroxing mirrors
Date: 11 Apr 92 21:21:03 GMT
Organization: Stanford Linear Accelerator Center

In article <8400009@trsvax>, pauls@trsvax.tandy.com says:

> Can somebody explain this to me??
> I tried to Xerox a flat mirror. The paper came out pitch black.
> Well??

I would suppose that a photocopier uses the diffuse reflection from
the document to be copied.  Paper does not have much specular
reflection (and that which it does have is not from the ink - try reading
a glossy magazine when the reflected light shines in your eyes).

Your mirror, having *ONLY* specular reflection, is as invisible to the
copier as the glass plate you put the paper on.
From: kibler@turing.ICS.UCI.EDU (Dennis Kibler)
Subject: simple question
Newsgroups: sci.physics
Date: 8 Apr 92 16:02:06 GMT

How is radioactive dating done?

 I understand that by knowing the current % (say Z) of X in Y,
and the half-life of X, that we can project backwards
and figure out the % (say Z') of X in Y at any previous time.
So to figure out the age of Y  we need to know the original
percentage of X in Y.  But how is that known?

 Let me put it in a more concrete form. Suppose we use carbon
dating to measure the age of a fossilized plant. I don't
understand why we aren't measuring the age of the carbon,
created I presume at the some time before the age of the earth,
rather than the age of the plant.

dennis
Xref: sparky sci.physics:6814 sci.skeptic:8138
From: rhc52134@uxa.cso.uiuc.edu (Richard)
Newsgroups: sci.physics,sci.skeptic
Subject: Re: Some quotes
Date: 16 Apr 92 16:29:14 GMT
Organization: University of Illinois at Urbana

ronnie@cisco.com (Ronnie B. Kon) writes:

>In article <1992Apr16.004905.7468@news.Hawaii.Edu>, vijay@wiliki.eng.hawaii.edu (Vijay Fafat) writes:

>|> St. Augustin (in reply to "What was God doing before creation?) : He was busy
>|> creating hell for people who ask such questions.

>1.  I really don't believe that St. Augustine qualifies as a physicist.

But he was answering a physics question!

>2.  He never said this.  He believed that God created time along with the
>universe--the question would be meaningless.  I'll go back and try to find
>the reference if somebody else doesn't give it first.

Whether it is he who said that is not important. The fact that what had been
said is interesting is.

Do not doubt the validity of quotas, they are not meant to be true.


-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Richard H Chiu, UI,Urbana-Champaign l                                           
e-mail:rhc52134@uxa.cso.uiuc.edu    l
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
From: aephraim@physics (Aephraim Steinberg)
Newsgroups: sci.physics
Subject: Re: What is not being conserved?
Date: 10 Apr 1992 20:51:43 GMT
Organization: University of California, Berkeley
NNTP-Posting-Host: physics.berkeley.edu

In article <1992Apr10.174714.4747@watson.ibm.com> platt@watson.ibm.com (Daniel E. Platt) writes:
>In article <s4htvINNc7f@agate.berkeley.edu>, aephraim@physics (Aephraim Steinberg) writes:
>|> In article <1992Apr9.213832.1911@hellgate.utah.edu> tolman%asylum.utah.edu@cs.utah.edu (Kenneth Tolman) writes:
>|>    {DELETED MOST OF EXCHANGE}
>|> readers of this newsgroup any more) what is selected out is a state of
>|> the entire atom+photon system, so if the photon is found to have gone off
>|> in the +x direction, the atom will be found to have recoiled in the -x
>|> direction, conserving momentum.  
>
>Actually, if you calculate the 'in' and 'out' states, and the
>transfer matrices, and calculate the cross-sections for various
>events, the cross-section for events that violate conservation are
>zero...
>
>You have a distribution of possible events in the shape of the
>dumbell, but the recoil that is ultimately detected in any one of
>those directions depends on the direction the photon was detected
>in on an event-by-event basis.

I must be missing something here, but how does that differ from what I
said except for the fact that it wisely avoided the word ``collapse,''
and replaced it with jargon?  We seem to agree that momentum is con-
served, and that this is manifested in nonlocal correlations between
the photon and the atom.




Not meaning to be dense,

aephraim



-- 
Aephraim M. Steinberg                    | "WHY must I treat the measuring
UCB Physics                              | device classically??  What will
aephraim@garnet.berkeley.edu             | happen to me if I don't??"
                                         |       -- Eugene Wigner
Newsgroups: sci.physics
From: sas52992@uxa.cso.uiuc.edu (Sanjay Ashok Sheth)
Subject: Re: Simple Light Question
Organization: University of Illinois at Urbana
Distribution: usa
Date: Thu, 9 Apr 1992 18:15:45 GMT

c60a-av@amazon.Berkeley.EDU (Vann) writes:

>First off, let me disclaim myself as a lowly h7b student, i.e. electromag-
>netics.Any response please tone down too pregraduate level, please...

>If time dialates and lenghts contract in the reference frame approaching
>the speed of light, then what about in the reference frame _of_ _light_?
>Is light everywhere at once as lengths contract to zero in the limit and
>time dialates until it stops? Would be hard to think the lorentz equations
>break down. Is there a way to distinguish between reference frames if light
>is everywhere in its own frame? ...

>I must be missing something, right? I'm sure this has been rehashed 
>innumerable times... once more couldn't hurt, no?

One of the postulates of relativity is that is is impossible, or better stated, requires an infinite amount of energy to go as fast as light. Therefore, it is  impossible to switch to a reference frame of light. Secondly, another postulate of relativity is that the speed of light is the same in all inertial frames.    If somehow, we did manage to shift into the reference frame of light, this 
would mean that the speed of light is zero which violates the above postulate.

You are right when you say that the lorentz equations break down but that is 
because they are not designed for the above scenario.

Sanjay Sheth
sas52992@uxa.cso.uiuc.edu
sas52992@sumter.cso.uiuc.edu (NeXT Mail)
From: carlip@landau.ucdavis.edu (Steve Carlip)
Newsgroups: sci.physics
Subject: Re: Vacuum Temperature
Date: 10 Apr 92 19:22:02 GMT
Organization: Physics, UC Davis

In article <1992Apr9.162500.9589@kakwa.ucs.ualberta.ca> anderson@fermi.phys.ualberta.ca (Warren G. Anderson) writes:
>In answering a recent post by Ronnie B. Kon, I stumbled upon an interesting
>question. Can one define a temperature for vacuums on curved space-times?
>If so, could some examples be given (your choice of vacuum and manifold)?
>
Sure.  This is one of the main results of quantum field theory in
curved spacetimes.  The definition of the vacuum in a quantum field
theory is not invariant; typically, a state that is the vacuum
for one observer will be filled with a thermal distribution of
particles for another.  For example, a comoving observer in
deSitter space will observe a thermal bath of radiation, as will
an accelerated observer in ordinary Minkowski space (in the latter
case, the temperature is kT = a/2\pi).  I'm sure there are
nontechnical references on this, but I don't know one off-hand;
if you want details, there are examples scattered throughout Birrell
and Davies, _Quantum fields in curved space_.

Steve Carlip
carlip@dirac.ucdavis.edu

Newsgroups: sci.physics
From: mvp@hsv3.uucp (Mike Van Pelt)
Subject: Re: "what's new" Apr-10-1992
Organization: Video 7 + G2 = Headland Technology
Date: Tue, 14 Apr 1992 01:28:09 GMT

In article <92101.162358WTU@psuvm.psu.edu> WTU@psuvm.psu.edu writes:
>WHAT'S NEW, Friday, 10 April 1992                  Washington, DC
 ...
>An Israeli Air Force expert said his study found no evidence that a
>Patriot ever took out an al Hussien warhead: "by that definition, the
>Patriot was a failure--and in a populated area there can be no other
>definition of success."  And yet, Israel is accused of selling Patriot
>technology to China.  Now that's a sale!

The fact that a screwdriver doesn't make a very good cold chisel
doesn't prove that it's a bad screwdriver, contrary to the logic
found in "What's New" columns like this one.

Those who don't subscribe to the "What's New" column's brand of
Politically Correct Know-Nothingism might consider it relevant that
the Patriot was designed for point defense.  Considering that area
defense of soft civilian targets was a use for which the missile was
never intended, akin to using a screwdriver for a cold chisel, it
performed pretty well.

Gee, I'd like to see a What's New ****IN PHYSICS!!!**** column...
-- 
"Pound for pound, lame puns are           Mike Van Pelt
 your best entertainment value."          ...ames!vsi1!hsv3!mvp
               -- Gogo Dodo               mvp@hsv3.lsil.com
From: menon@ftp.phy.uab.edu (Govind Menon)
Newsgroups: sci.physics
Subject: idealizations??
Date: 15 Apr 92 17:31:42 GMT
Organization: University of Alabama at Birmingham

The case of the hard sphere and plane is an interesting scenario, but by no 
means realistic.  If however, you do wish to conduct a thought experiment, 
constrained to idealizations, then permit me if you will to make yet another
reasonable assumption.  

There is nothing preventing a perfectly spherical and a perfectly planar 
material from being infinitely rigid.  Subject to this condition the bodies
do not have to deform under infinite pressure at the contact point.  

cheerio,
         Govind Menon
From: frank@evax2.engr.arizona.edu (Frank Manning)
Newsgroups: sci.physics
Subject: Re: Xeroxing mirrors
Date: 13 Apr 92 18:06:03 GMT
Reply-To: frank@evax2.engr.arizona.edu
Distribution: world,local
Organization: University of Arizona, College of Engineering and Mines, Tucson

<8400009@trsvax> pauls@trsvax.tandy.com:

>I tried to Xerox a flat mirror. The paper came out pitch black.

You know, it occurred to me you'd get the same result if you put a
second Xerox machine upside down on the first one, aligned the glass
plates, and operated them simultaneously.

-- Frank Manning                                -- I'm not a child of nature,
-- College of Engineering and Mines             -- I'm a child of asphalt.
-- Civil Engineering 100, University of Arizona --
-- Tucson, AZ  85721    frank@evax2.arizona.edu --        _Northern Exposure_
From: sichase@csa2.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: What Are Photons?
Date: 9 Apr 92 19:25:04 GMT
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
Distribution: na
Reply-To: sichase@csa2.lbl.gov
NNTP-Posting-Host: 128.3.254.197
News-Software: VAX/VMS VNEWS 1.3-4   

In article <1992Apr9.014622.6667@wubios.wustl.edu>, david@wubios.wustl.edu (David J. Camp) writes...

>Which of the 12 fundamental particles are photons?
>Is the photon a clump of 2 or more particles?

None of the above.  There are 12 fundamental FERMIONS (of which we know).
The photon, along with W,Z, gluons, and graviton, are BOSONS, which are
distinct fundamental particles which mediate the forces between the 12
fundamental fermions.  

Each fermion also has an antimatter partner.

There are other particles in the zoo, none of which have been observed, but
which are expected to exist based on various theories of varying credibility.
These include the Higgs (gives mass), axion (prevents strong CP violation),
Supersymmetric partners to all of the above (to control the masses of some of
the other particles), Familons (to explain the seemingly broken family
symmetry), X and Y bosons (useful for Grand Unification), right-handed W and Z
(so that parity is not violated in the unbroken theory), and so on, ad nauseum.

> 
>What kind of radiation is emited by the interference pattern of
>magnetic fields?
> 

Huh?  

-Scott
From: assib@acad2.alaska.edu
Newsgroups: sci.physics
Subject: Heard of VIRTUAL PARTICLES???
Date: 10 Apr 92 03:34:48 GMT
Article-I.D.: acad2.1992Apr9.233448.1
Organization: University of Alaska

The other day a friend of mine mentioned 'Virtual Particles...'
Could I get some more info on this?

If you have any feedback, send to:
----------------------------------
      ASSIB@ACAD2.ALASKA.EDU
Newsgroups: sci.physics
From: kyee@bnlux1.bnl.gov (kenton yee)
Subject: Re: Sciencists/politics (was Hawking speaks out ...)
Organization: Brookhaven National Laboratory, Upton, NY 11973
Distribution: world,local
Date: Sun, 12 Apr 1992 01:55:25 GMT

In article <COLUMBUS.92Apr9094825@strident.think.com> columbus@strident.think.com (Michael Weiss) writes:
>In article <9382@vice.ICO.TEK.COM> hall@vice.ICO.TEK.COM (Hal Lillywhite)
>writes: 
>   Unfortunately movie stars can support political candidates or causes
>   and people (including the media) give them coverage as though they
>   knew something special.  Scientists usually don't get as much
>   attention (unless they speak out in support of some popular or
>   politically correct idea)....
>Well, movie stars sometimes get elected, so maybe that makes their opinions
>weightier than those of mere scientists :-))  

  Of course, the *role* of politicians is to sell/explain 
  policies/ideas to the people, so it makes sense that movie
  stars are taken more seriously by the media than scientists...
  The question is... who influences Jane Fonda, and tells her
 what to say?
From: sichase@csa1.lbl.gov (SCOTT I CHASE)
Newsgroups: sci.physics
Subject: Re: mass definition in particle physics
Date: 10 Apr 92 18:07:03 GMT
Organization: Lawrence Berkeley Laboratory - Berkeley, CA, USA
Distribution: na
Reply-To: sichase@csa1.lbl.gov
NNTP-Posting-Host: 128.3.254.196
Keywords: mass, particle physics
News-Software: VAX/VMS VNEWS 1.3-4   

In article <10APR199210204620@deimos.ucc.umass.edu>, s5169180@deimos.ucc.umass.edu (S5169180) writes...
>>Brahm at Caltech wrote :
>>Mass is the pole of the propagator. ...
> 
>I absolutely agree with that argument. Therefore finding mass is same to
>finding bump in the cross section. It has a very useful meaning
>phenomenologically. However it can't give the reason how or why a particle has
>a specific physical(or numerical) value. My question is if we can predict
>masses of quarks or leptons purely in theoretical way, instead of experiments.

Sure.  Check out Physical Review Letters or Physical Review D on any typical
week.  You'll find many theoretical explanations of the mass spectrum of the
quarks and/or leptons.  The problem is that we don't know which, if any, 
are correct explanations.  In the absence of additional experimental evidence
for which theories are correct, it's just speculation.  

By the way,

I would say that the pole of the propagator is the mass, not the other way
around.  You write a wave-equation and solve it for the Green's function.  It
turns out that the propagator has a pole when the particle is on-shell.  I
suppose you could just postulate things in the reverse order, but you don't
learn anything by doing that.  

-Scott
From: paul@mtnmath.UUCP (paul)
Newsgroups: sci.physics
Subject: Re: My objections to the collapse postulate
Summary: How information is transferred without being able to signal.
Date: 11 Apr 92 17:08:28 GMT
Organization: Mountain Math Software, P. O. Box 2124, Saratoga. CA 95070

In article <1992Apr10.212404.2528@math.okstate.edu>, gindrup@math.okstate.edu (Eric `'d'kidd' G..) writes:
>...The information that the second
> observer obtains does not travel between observers faster than light, because
> the second observer cannot know whether either observer was actually
> "there" when the photon collapsed.
> ...
> What's the problem?

That information is transferred instantaneously in singlet state quantum
collapse without being able to send a signal has been mentioned in this
discussion many times, but it is a subtle and confusing point. The best
intuitive explanation I have is based on cryptography. A perfect one time
pad in cryptography is generated by taking the exclusive or of each bit
in the message with a bit in a perfect random sequence. (I am ignoring
for the moment that I don't think there exists any such thing as a perfect
random sequence. :-) It is impossible to decrypt such a message without
knowing the pad or key because the encrypted message is also a perfect
random sequence.  Now suppose we have one observer transmitting a bit
sequence to a second distant observer. Some times the first observer sends
random bits and sometimes he sends a message encrypted with a perfect one
time pad. The receiver cannot know when a message is being sent. The sequence
he receives is equally random in either case. Now suppose the transmitter
gives the receiver the pads he was using. The receiver can use these pads
to determine when the messages were sent and to decrypt them. He can measure
precisely when the encrypted message was transferred even though he was
not able to decrypt the message at the time it was sent or even able to
know that a message was being sent at that time. 

This is precisely the situation with singlet state quantum collapse. The
perfect random pad is provided by quantum uncertainty. The transmitter in
such an experiment sends an encrypted message by varying the angle of a
polarizer. This is received as a series of detections. These detections
appear completely random. However they are precisely correlated with
an encryption key provided by quantum uncertainty. We know what this
encryption key is (it is the observed detections at the transmitting site).
We can communicate this key to the remote site (but not faster than the
speed of light) and this key can be used to both decrypt the message and
to measure precisely when the encrypted message or information was
transferred. Using this technique we can prove that the remote observations
were instantaneously correlated with the local observations and manipulations
of a local polarizer. This technique will allow us to experimentally verify
that information (the encrypted message) was transferred instantaneously
in the unlikely event that the instantaneous collapse postulate is true.

Paul Budnik