The aim of physics is to find accurate descriptions of Nature. Over the centuries, this task has split up in several sub-domains. Since mathematics has proved reasonably effective to describe Nature, it is no surprise that a considerable amount of attention is dedicated to the mathematical formulation of our theories. That's mathematical physics and the one end of the spectrum.

At the very other end there's experimental physics: That's going out and bringing in real-world data with all the required analysis and errorbars. If I learned one thing in my experimental physics classes, it's to never forget those errorbars. The other thing I learned is that oscilloscopes are allergic to my presence.

In between mathematical and experimental physics, there's theoretical physics and phenomenology, with theory leaning towards the math, and phenomenology leaning towards experiment.

Theoretical physics is the construction of theories. (Depending on your philosophy you might insist it's a discovery rather than a construction, but I'm not a philosopher, so please excuse.) Theory inevitably brings a considerable amount of math but the focus is on finding a description of Nature. Once you start up with some theory, the requirement of mathematical consistency puts very strong constraints on what you can and can't do, and it can take substantial time and effort to figure out the details. It's thus no surprise the boundary between theoretical and mathematical physics is fuzzy. Historically, both have often proceeded hand in hand with each other.

In contrast to math though, it happens frequently that theorists work with assumptions that have not been proven to be true but there are physical arguments to believe they are true or, if not true, then there are at least reasons to believe that they work. Theoretical physicists thus have a freedom of intuition that mathematical physicists don't have. The result is that the mathematical physicist will typically tell the theoretical physicist he's sloppy, while the theoretical physicist will call the mathematical physicist a nitpicker.

The emphasis of phenomenology is on developing models either for already available experimental data, or for theories for which a connection to the data is so far missing. Phenomenological models are not meant to be a fundamental description of Nature. Their purpose is to connect the theory with the experiment, both ways. This typically happens by making simplifying assumptions or considering limits in which only some features of a theory are relevant. On the other hand, if you have a phenomenological model that describes the data very well, you can extract from it some of the features the underlying theory must have. Note however that the derivation is one-way: You can, in principle, derive a phenomenological model from the full theory, but not the other way 'round. The result is that the theorist will typically look down on the phenomenologist for lacking closeness to fundamental truths, while the phenomenologist will consider the theorist a dreamer.

Needless to say, there is no strict boundary between phenomenology and theory either. For example, you can very well have a phenomenological model that however makes predictions that are not observable, or not yet observable. So it doesn't provide much of a bridge to experiment. On the other hand, the more parameters you use in a model, the closer it gets to data-fitting and the less useful it is to extract something of fundamental value. But well, what would the world be without friction?

I originally studied mathematics and have a Bachelor's degree in math rather than physics. Today I'm a phenomenologist because I know I have a tendency to get lost in mathematics. It's a very wide world, the world of mathematics. There are many people who have the courage to search for fundamental truths following nothing but their intuition, but I prefer to have reality constraints. The underlying reason is that I believe mathematical consistency alone is not sufficient to arrive at the right theory.

Why I work on the phenomenology of quantum gravity in particular is that I believe quantum gravity is where our next major step forward will be and I think it will revolutionize our understanding of reality. Some of my more optimistic colleagues think observations are a decade away. I think it's more likely two or three decades. Occasionally, people who know what the Planck scale is laugh when I tell them I work on the phenomenology of quantum gravity. Well, if you'd have told them three decades ago that we'll one day be able to distinguish different inflation scenarios by high precision cosmology, they would have laughed as well. So, no, we're not there yet, but I'm confident it's in our future.

## 42 comments:

Why I work on the phenomenology of quantum gravity in particular is that I believe quantum gravity is where our next major step forward will be and I think it will revolutionize our understanding of reality.Agreed, unless of course we live in a universe where quantum gravity does not exist, in which case the falsification of QG will do just as nicely, so your lifelong project and upcoming conference are way, way important. How's that coming by the way? How many days away is it? How many Experimentalists are you inviting?

Remember the mind set of Engineers, Bee.

Day 1: Ask an Engineer (Experimentalist to you) to do something. He tells you it's impossible.

Day 3: Talk to him again. He tells you after some thought it's possible, but it will be too expensive.

Day 5: Again. He tells you he's figured a way to cut the costs to barely doable, but it's still too expensive.

Day 7: He's figured a way to do it at reasonable cost, but good luck getting the funding, and that's not my job and good luck with that.

Day 8: Call up the King of Sweden.

:-)

Hi Steven,

Quantum gravity does not "exist" is not an option. Quantum gravity is generally referred to as the reconciliation between classical general relativity and quantum field theory, but it's more than this, it's a completion. There are simply regimes we cannot today describe using either of our known theories, yet we know these regimes are part of Nature. There has to be some theory that describes these. What you possibly mean is that gravity is not quantized, or that possibly the attempt to do so isn't meaningful, which might be, but that's a different thing.

Thanks for asking, the workshop organization is going reasonably well. Still trying to get the abstracts in, see website. Trying to sort out the apartment booking. (Noticed yesterday two speakers were booked into a one-bedroom apartment.) Stuff like that. Best,

B.

Hi Bee,

In brief, you are a

modeller, and not atheorist. You are supposed to bring theorists back to reality by constraining the feet of their dream to the ground. Do you make a lot of friends doing so?Best regards,

Nice manifesto!

-Arun

There has to be some theory that describes these.I certainly hope so. It's what attracted me to BackReAction in the first place. I am but a poor QG

hobbyist, but you're a QGprofessionalso I defer to your opinion on these matters.However, your remark inspired me to write a super-short story, by analogy, and possibly a bad analogy.

QUANTUM GRAVITY and the BATTERY DUDE

Once upon a time there was a little dude who lived in a civilization inside a car battery. He was brilliant, but had no idea that there were two posts on the outside of the battery, an anode and a cathode.

So he surmised that power must come from somewhere, so he surmised a single "ode" he called a "superode". It simply must be, he said. Two "odes" would unnecessarily complicate my sulfuric acid universe.

One day he dreamed a dream and connected with his also-dreaming "god," the owner of the car in which he resided, and asked him if his theory was right.

"No," said the owner. "There's two battery posts, an anode and a cathode. They operate somewhat differently, but they exist in your universe at the same time."

"Really? Damn."

"Or toughski shitski as they say in Poland."

"What's a Poland?"

"Nevermind. So, what are you going to do now? Abandon you theory and work on the correct one?"

"Heck no."

"Hmm? Why not?"

"Because, I don't believe you or anything else I can't see. I'm a Positivist! Anyways, the politicians who fund me don't know anything about Science, and they know nothing about this conversation. I'm going to request even MORE money for Superode Theory!"

"Hmm, well you

couldbe ope-minded like Lee Smolin in our Universe and request funding for all possibilities.""Yeah, maybe. I'll think about it."

"Or you could ask the Engineers."

"What? The friggin' gearheads?! What do

theyknow?""Limits and constraints?"

The End

Very nice explanation!

I think part of the problem is "phenomenology" also has some related meaning in philosophy so people are even more apt to get confused.

Now, that I have an idea what "phenomenology" is it actually sounds really fun! If I was a physicist I think I would like to be a phenomenologist, I like trying to explain data.

...Maybe in a parallel universe I am ;-)

/* mathematical consistency alone is not sufficient to arrive at the right theory..*/

It was experimentally proven by Ptolemy's model of epicycles - it was a brilliant theory, "just" dual to observable reality.

Anyway, the fuzziness of string theory and quantum gravity landscapes is indicating, we shouldn't overestimate even the consistency of pure formal theories.

http://www.physorg.com/news142516533.html

For example, string theory considers Lorentz symmetry and extradimensions at the same moment, albeit extradimensions should manifest itself just by violation of LS. Such theory can never remain consistent at formal level, because it's fringe logically. Quantum gravity suffers the same inconsistency problem regarding equivalence principle, just in more subtle way.

http://en.wikipedia.org/wiki/Pauli_effect Bee is a theorist.

http://en.wikipedia.org/wiki/Dark_Star_(film)

"'teach the bomb phenomenology,' resulting in a memorable philosophical conversation between Doolittle and the bomb."

"theorists work with assumptions that have not been proven to be true but there are physical arguments to believe they are true"http://www.mazepath.com/uncleal/erotor1.jpg

Theory predicts what observation tells it to predict. When theory ignores reality for "higher truths" it excretes economics and string theory.

Heuristics are good - to a point. The Golden Gate Bridge is Newtonian. Even then, absent some resonance-breaking foothills it would have been another Galloping Gertie. Embrace serendipity but do not depend upon it.

Theory is not enough! We must have shipping docks (and waste crocks).

Bee:but I prefer to have reality constraints. The underlying reason is that I believe mathematical consistency alone is not sufficient to arrive at the right theory.For those of us that have hung for quite a while now tend to know this of you.

I saw the term used a few years back when Jo Anne of Cosmic Variance was using this in her endeavours. Imagine using your science to fix the natural tendencies of a drive way using the science mind? Or, like Clifford fixing a Sun deck.

This is part of the reality adjustment of using the trade in concert with the ideas of phenomenological association and application of science "to" other areas. Science and economics. Not to waste talents on wall street.

Sitting on the science boards as to the direction of and outlay of money to be determined in the direction in spending of science fundings. John Ellis as well, and others scientists who are funding for the future and delivery's of science.

So for me this is a positive step forward in the whole science process.

I tend to see into the future, with the understanding that quantum gravity is a personal relation "that smells of the mystic," but is to me relevant to our relationship with the natural world. You can't see it, so it is not true you see.:)I am not saying one has to be irresponsible. How else can you apply this vision to the future under such a mandate?

This has a serious effect on the future of where it's applications will be used.

I believe our science will one day show this when it is understood how quantum integration of the very large with the very small is successfully applied to everything( any ideas?)

But of course that's ,my opinion.

Best,

Bee:

Do you regard the ADS/CFT conjecture as something mathematical or a feature of nature? What is your opinion of this as it relates to QG? Thanks.

The Unreasonable Effectiveness of the Human Brain

Surely, you jest overtly to Tegmark, for over the years it was obvious where you were coming from.

It's just part of the discovery of who you are (I am who I am) as it is revealed through each posting.

That is how you get to know yourself and how the interconnecting neurons are linked in blog postings.

So where you headed?

IN all that you have learnt let's assume the world is objectionable in terms of the quantum gravity issue, and if it were so, how would the world change. How would would you apply phenomenological order to the world around you, so it is, simple for each of us to understand an outcome.

A fictional writer perhaps who has been grounded in the sciences, to reveal facets of the thinking mind in it's potential, will and can become the reality?

Best,

It never hurts sometimes to clarify one's position before moving into concrete absolutions of ideas about that future.

Sean Carroll did it with David Albert on talking heads, as a formal step to explaining his position?

Beyond the traditional schools

Rather than focus on narrow debates about the true nature of mathematical truth, or even on practices unique to mathematicians such as the proof, a growing movement from the 1960s to the 1990s began to question the idea of seeking foundations or finding any one right answer to why mathematics works. The starting point for this was Eugene Wigner's famous 1960 paper The Unreasonable Effectiveness of Mathematics in the Natural Sciences, in which he argued that the happy coincidence of mathematics and physics being so well matched seemed to be unreasonable and hard to explain.

The

embodied-mind or cognitive school and the social schoolwere responses to this challenge, but the debates raised were difficult to confine to those.(

Bold added by me for emphasis)Hi Plato,

I don't know where I'm headed. My opinion on what's the most promising way towards insight has changed over time, and it might very well continue to change. Best,

B.

Hi Jérôme,

Different people have very different attitudes towards their research. For some it's their peers' attention that matters and waking them up from a dream is very unpleasant. For others it's the understanding that matters and dreaming is a waste of time. I get along well with the latter and very badly with the former. I don't care very much if that makes me friends or not - the number of friends is not a quantity I strive to maximize ;-) Best,

B.

clkirksey,

The AdS/CFT conjecture, being a conjecture, is not yet mathematical in the sense that a proof is missing. It might well be in the future we'll have such proof. The conjecture has meanwhile proven to have explanatory power for several examples of real world systems, so it is definitely useful. It is in fact an excellent example for how theoretical physics differs from mathematical physics. I'm not sure what you mean with whether it's a "feature" of Nature. To me theories or models aren't features or non-features, they work or they don't work. How that relates to QG I think nobody really knows. Or those people who think they know are deluding themselves. Without any observational evidence, there's no knowing. Best,

B.

/*..they ask me if I'm in experiment or theory. And I'll tell them I'm a phenomenologist..*/

If you're not doing any experiments, then you're a theorist. But frankly, you're "just" an "applied mathematician".

I wonder where you would put 'computational physics' in the math/phys/experiment spectum :-)

Cheers!

Not sure what you mean with that. Do you mean numerics? It's part of the full spectrum with the importance decreasing from experiment towards maths. Best,

B.

Hi Bee,

Thanks as that was a good explanation of what you find as being your main emphasis in research in respect to the overall spectrum. I recall it being it just a few days ago that you complained I was putting you in a box in referring to you as a phenomenologist and now I can better appreciate why. Then again I would say you’re not completely forthcoming as to where your interests lie or methods be, in suggesting you’re not much of a dreamer. That being as on the contrary I imagine you dream quite a bit, yet in doing so knowing full well that’s what it is, with the difference being you are checking all the while if these dreams might be consistent with what is real. Also I do find you as someone who holds true to your instincts, with just one example being convinced there existing a minimal length, as to find our world as being discrete at the fundamental level.

Yet what I find most that gives you away is you are always looking at other’s dreams to see if they are reasonably sound or not, with your box problem being most indicative of that. So despite knowing you don’t like being put in a box, the physicist you leave me most mindful of is the late, great J.S. Bell. That is I see you as him being a dreamer, who with his dreaming was most suited and capable in discovering if the dreams of others could possibly compare with the best of them all, with that being the one known as reality.

“But if there be any man who, not content to rest in and use the knowledge which has already been discovered, aspires to penetrate further; to overcome, not an adversary in argument, but nature in action; to seek, not pretty and probable conjectures, but certain and demonstrable knowledge — I invite all such to join themselves, as true sons of knowledge, with me, that passing by the outer courts of nature, which numbers have trodden, we may find a way at length into her inner chambers.”-Francis Bacon- Novum Organum

Best,

Phil

Hi Phil,

Yes... the title of the post is somewhat tongue-in-cheek. As you said earlier, trying to put me in a box is like trying to put one of the funny photons in a box. Depending on how you look at it, the photon won't be in the box. I should have called that the "parabox" I suppose ;-) Best,

B.

Hi Bee,

Yes perhaps you should have called it the parabox and I suggest that over time you may find some frustration as Bell did in having understood what serves as being the distinction. In looking again at Bacon’s words I find his failing as not being enough of a dreamer, as he imagined only men could pass beyond nature’s outer courtyard to discover what to be within. So therefore Bacon could not have possibly been Shakespeare as he demonstrated and respected women as being far more capable:-)

Best,

Phil

Hi Bee!

Do you happen to know if anyone visiting the workshop is interested in testing QG by looking for a Lorentzlike deviation from the SR shift laws?

Namsrai used stochastic arguments to suggest that the spacetime around moving particles is distorted in a way that expresses their state of motion (effectively, a velocity-dependent gravitomagnetic effect). That curvature would represent a departure from Minkowski spacetime, and change the shift predictions for a moving object, and if we need the distortion effects to be compatible with the principle of relativity, we'd then be looking for a "Lorentzlike" deviation to the red of SR, of ( [1-vv/cc]^(something) ).

Interestingly, it seems that the SR-testing guys have traditionally been told that only deviations to the //blue// of SR need to be taken seriously - results redder than SR are supposed to have no theoretical significance, and test theory lets experimenters calibrate out or compensate for any overshoots to the red.

Nobody seems to have seriousuly considered the possibility that these overshoots might be genuine. If they are ... boom ... you've got yourself a quantum gravity testing goldrush! :)

(If they're not, at least it'd be one more gap in our testing procedures filled).

It might be considered a longshot, but it should be doable with 1980's technology.

Is "Quantum Gravity" the best name for the field of study that mutually interests us, Bee? It seems to put "Quantum" before General Relativity. Is this right?

"Gravitic Quanta" seems ugly, so I do not suggest that.

"Continua Discrete" seems more descriptive, yet uglier still.

I give up. Your thoughts, Bee?

If the axioms of physics were finitely innumerable, then there would exist a sequence of natural numbers that could not be mapped to any possible physical experiments.

This is a nearly immediate result of Godel's Incompleteness Theorem.

Steven,

Don't know what's wrong with calling it quantum gravity. Something appealing to discreteness is very misleading. Who says that the theory we're looking for features a discrete spacetime structure? You might find this amusing. Best,

B.

Hi ErkDemon,

I'm not sure what you mean with "SR shift law." Do you mean gravitational red/blue shift? How is that SR if you have curvature? How is it Lorentz-invariant if it depends on the velocity of the particle? (Go into a restframe where the particle doesn't move.) Either way, there's a whole bunch of such propagation effects that will be discussed at the workshop. Best,

B.

Hi Bee,

I think what Steven is driving at being that with a QG theory it’s assumed that at the Planck scale all aspects of substance and force will be dictated by rules consistent with quantum mechanics, rather then those of General Relativity. That it being at such resolution gravity will not be distinguishable from any other force, yet only an emergent phenomena of a unified field. However, I prefer to simplify this a bit further, to say that almost all current efforts carry with it the metaphysical assumption that the world fundamentally only explainable in terms of a singular ontology. For what its worth I don’t think there is sound enough reason to accept this assumption, as there is equally good reason that the world may be only definable fundamentally within the confines of no less than a dual ontological framework. If this were to be found true then the rules of both the quanta and GR would then necessarily be emergent aspects of nature,

Best,

Phil

You think correctly Phil, though I hope I'm wrong. Nothing would please me more than to live long enough to see a set of field equations that combines quantum mechanics and general relativity, or some paper based on the simplest and fewest assumptions and Aristotelian logic that proposes a test ala Bell's Inequality that would confirm one way or the other that a QG theory is possible or impossible. I had that original thought yesterday morning shortly after waking up too soon as usual (given my insomnia) in the wee hours. I'm sure I'm not the first one to have it given the history of science.

Hi Bee, Iceland's volcanic ash in the atmosphere might be giving you some spectacular sunrises and sunsets?

-Arun

If they keep cancelling flights, I might have to enjoy them without Stefan though...

Hi Steven,

Well I would say QG is a subject that many who actually get paid to worry about it have lost a little sleep from time to time. Personally I like the way Bee is working at this time with her phenomalogical approach, as it gives what better has to be explained, rather than making even more assumptions. Interestingly this is the way J.S. Bell approached physics and I wished more did the same, as many theorists are lost with little to guide them other then beautiful mathematics.

There are times in physics when we need new dreams and yet all this is useless unless these dreams can be examined for their soundness in being able to match reality. So what Bell did with his inequality and Bee with her box problem ia not to give us a new dream, yet rather set parameters for which of them can be true and which cannot. Then again there are those dreamers who see such results only to ignore what they tell us, like all those still out there who despite what Schrodinger demonstrated believe what it confirmed is that a cat can simultaneously be both dead and alive:-)

Best,

Phil

Tommaso Dorigo cites a recent arXiv paper by Paul Howard Frampton at his website: here, titled "Solution to the Dark Energy Equation."

I am not qualified to comment, but you are Bee, as Arun Gupta points out in the replies. What say ye, Bee? Here from the very short pre-print is Dr. Frampton's relevant conclusion, as Dr. Dorigo points out:

My result calls into question almost all of the work done on quantum gravity, since the discovery of quantum mechanics. For gravity, there is no longer necessity for a graviton.

In the case of string theory, the principal motivation for the profound and historical suggestion by Scherk and Schwarz that string theory be reinterpreted, not as a theory of the strong interaction, but instead as a theory of the gravitational interaction, came from the natural appearance of a massless graviton in the closed string sector.

I am not saying that string theory is dead. What I am saying is, that string theory cannot be a theory of the fundamental gravitational interaction, since there is no fundamental gravitational interaction.

... Paul Howard Frampton

As said, it makes me scratch my head. I must say I was never happy with the "graviton" as a "particle." As a "phonon", which Erik Verlinde implies? Yes, that would make more sense. And if the "graviton" is a phonon, why not all the other

fundies(fundamental particles")?The analogies in terms of sound as an inclination toward understanding of gravity has been expressed a lot. Forms the basis of my own blog experience. Try and do away with the graviton and you do away with the closer reality of the understanding of that continuity?

"Continuity of expression and the quantum level" would run into trouble if we were to still consider it just as a "discrete function?"

So this is indeed part of the problem, and a sort of epiphany has taken hold these last couple of weeks as well.

Part of this has to do with the understanding "that reductionism has lead us to a place" that while seemingly delusional(color of gravity in my own artistic sense), is as if, the large and the small are part of that holism that seeks to find the basis of what ends in reductionism brings us back to the a larger picture. "Is" never really separated.

The thought exchanged over the years crossed my mind of course, but the basis of the experience to find this connection has always been there waiting to be "topologically expressed" in my view.

"The math" has always been placed outside of us as a expression of the universe in topological defined movements.

It is strange how this came to enlighten in terms of a "politico resolute" while studying the experiments and thoughts that are constantly being defined in terms of experiments(discretism).

Photonically expressed, as some parabox, it had historically already been moved to the idea of the electromagnetic joined with gravity.

To arrive at a gravitational conclusion (inclusion of maxwell's equations)with Einstein, it just made sense to move forward under the same pretext of comparison drawn about what that joining of the large and the small would mean.

Seeing the "slide of light" in this context in relation to lensing just made sense. So your delusional at this point?:)

There is a very large contingent of many who have considered this problem to date.

Best,

Hi Steven,

I had read the paper. Frampton is certainly very... self-confident. I'm not sure what to make out of this. I might think about it somewhat further. If I come to any conclusions, you'll find it on this blog. Best,

B.

Hi Bee,

it is interesting and isn't it uncommon, that someone started as a mathematician and end up as a phenomenologist. However I can follow your reasoning for this.

Best Kay

Hi Bee,

Paul Frampton has a guest blog article at Lubos Motl's The Reference Frame up today, here.

Frampton has a copyright 2010 book to sell, btw, included in his very short essay. Well, who doesn't?

In any event, your comments would be most welcome, as you're the "Pro from Dover" on things quantum gravity. As a former Thermodynamicist I'm all over Entropy (our baby) and am reviewing the theory (trawling out learned but "forgotten" facts from old neurons) re same and hope to add to the discussion within a week.

At issue is the elusive "graviton." Frampton states that one can have a gravitational field without a gravitational particle. Lubos takes issue of course in the replies section. Great irony and understandable, as the primary reason given by Ed Witten for leaving the world of Science (Physics) for Language (Mathematics - Superstrings division) in 1983 is because a spin-2 massless particle "fell out" of the new equations, that Susskind et. al. instantly dubbed "the graviton."

Hi Bee,

I've taken your advice to "specialize in generalizing" which isn't as bad as I thought, since there are so damn many specialties in Physics alone! In any event, I think I may be on the verge of writing my first paper, and as my (unasked-to-be-but-are-nevertheless) mentor, it would be appreciated if you & Stefan would click here to see if I got anything horribly wrong, thanks.

Hi Bee,

I've taken your advice to "specialize in generalizing" which isn't as bad as I thought, since there are so damn many specialties in Physics alone! In any event, I think I may be on the verge of writing my first paper, and as my (unasked-to-be-but-are-nevertheless) mentor, it would be appreciated if you & Stefan would click here to see if I got anything horribly wrong, thanks.

I first heard about phenomenology in the movie Dark Star. Their sun destroying mission had gone awry, and one of their star blasting bombs refused to detach and was arguing with them, so they woke up their dead captain, and he suggested they talk to the bomb about phenomenology. If I remember correctly, phenomenology is the study of what we can learn from our own direct experience. In the case of physics, this consists of the stuff on instrument displays and computer program outputs, and it appears that we can learn quite a bit.

P.S. Bee: You sort of starred in that Science magazine article on speed of light wavelength dependence. Yes, I read the paper version so I'm weeks behind. Congratulations.

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