Showing posts with label Sean Carroll. Show all posts
Showing posts with label Sean Carroll. Show all posts

Sunday, November 13, 2016

Dark Matter and Dark Energy Information

The importance of the CMB, while a snapshot of the early universe just after 380000 years after the big bang is a materialist point of view, other things were born, as with the idea about the current state of the universe. What is dominating in terms of dark energy.


Talking About Dark Matter and Dark Energy

So here is one I did this morning, about why cosmologists think dark matter and dark energy are things that really exist
See also:


Emergent Gravity and the Dark Universe by Erik P. Verlinde

Recent theoretical progress indicates that spacetime and gravity emerge together from the entanglement structure of an underlying microscopic theory. These ideas are best understood in Anti-de Sitter space, where they rely on the area law for entanglement entropy. The extension to de Sitter space requires taking into account the entropy and temperature associated with the cosmological horizon. Using insights from string theory, black hole physics and quantum information theory we argue that the positive dark energy leads to a thermal volume law contribution to the entropy that overtakes the area law precisely at the cosmological horizon. Due to the competition between area and volume law entanglement the microscopic de Sitter states do not thermalise at sub-Hubble scales: they exhibit memory effects in the form of an entropy displacement caused by matter. The emergent laws of gravity contain an additional `dark' gravitational force describing the `elastic' response due to the entropy displacement. We derive an estimate of the strength of this extra force in terms of the baryonic mass, Newton's constant and the Hubble acceleration scale a_0 =cH_0, and provide evidence for the fact that this additional `dark gravity~force' explains the observed phenomena in galaxies and clusters currently attributed to dark matter.

Wednesday, May 25, 2016

Tuesday, May 05, 2015

The Mera Lattice

There are reasons this information is meaningful to me and I hope to explain myself shortly.
Consistency Conditions for an AdS/MERA Correspondence

The Multi-scale Entanglement Renormalization Ansatz (MERA) is a tensor network that provides an efficient way of variationally estimating the ground state of a critical quantum system. The network geometry resembles a discretization of spatial slices of an AdS spacetime and "geodesics" in the MERA reproduce the Ryu-Takayanagi formula for the entanglement entropy of a boundary region in terms of bulk properties. It has therefore been suggested that there could be an AdS/MERA correspondence, relating states in the Hilbert space of the boundary quantum system to ones defined on the bulk lattice. Here we investigate this proposal and derive necessary conditions for it to apply, using geometric features and entropy inequalities that we expect to hold in the bulk. We show that, perhaps unsurprisingly, the MERA lattice can only describe physics on length scales larger than the AdS radius. Further, using the covariant entropy bound in the bulk, we show that there are no conventional MERA parameters that completely reproduce bulk physics even on super-AdS scales. We suggest modifications or generalizations of this kind of tensor network that may be able to provide a more robust correspondence. See:

See Also:

Sunday, April 28, 2013

Getting Perspective on Time

Time has no independent existence apart from the order of events by which we measure it.Albert Einstein

Currently with the new book written by Lee Smolin about Time, to me, it is a fundamental question about what arises, and,  on how we use time to measure. Also for me,  to ask what relevance time means,  as an emergent product for any beginning.

LEE SMOLIN- Physicist, Perimeter Institute; Author, The Trouble With Physics

Thinking In Time Versus Thinking Outside Of Time

One very old and pervasive habit of thought is to imagine that the true answer to whatever question we are wondering about lies out there in some eternal domain of "timeless truths." The aim of re-search is then to "discover" the answer or solution in that already existing timeless domain. For example, physicists often speak as if the final theory of everything already exists in a vast timeless Platonic space of mathematical objects. This is thinking outside of time. See: WHAT SCIENTIFIC CONCEPT WOULD IMPROVE EVERYBODY'S COGNITIVE TOOLKIT?
 A "scientific concept" may come from philosophy, logic, economics, jurisprudence, or other analytic enterprises, as long as it is a rigorous conceptual tool that may be summed up succinctly (or "in a phrase") but has broad application to understanding the world.

What ignited this question for me goes to a comment I wrote as to what I saw as a precursor to this question for Lee Smolin and others. Further to this, the lessons and explanation Sean Carroll gave toward how we look at time.

Darwinian evolutionary biology is the prototype for thinking in time because at its heart is the realization that natural processes developing in time can lead to the creation of genuinely novel structures. Even novel laws can emerge when the structures to which they apply come to exist. Evolutionary dynamics has no need of abstract and vast spaces like all the possible viable animals, DNA sequences, sets of proteins, or biological laws. Exaptations are too unpredictable and too dependent on the whole suite of living creatures to be analyzed and coded into properties of DNA sequences. Better, as Stuart Kauffman proposes, to think of evolutionary dynamics as the exploration, in time, by the biosphere, of the adjacent possible. See: Thinking In Time Versus Thinking Outside Of Time
While we then become cognoscente of the rules around which parameters have meaning in relation to Time, it was also important to understand that the idea of cross pollination of the sciences recognizes what is brought to the table.

"It is very good that Stu Kauffman and Lee are making this serious attempt to save a notion of time, since I think the issue of timelessness is central to the unification of general relativity with quantum mechanics. The notion of time capsules is still certainly only a conjecture. However, as Lee admits, it has proven very hard to show that the idea is definitely wrong. Moreover, the history of physics has shown that it is often worth taking disconcerting ideas seriously, and I think timelessness is such a one. At the moment, I do not find Lee and Stu's arguments for time threaten my position too strongly."- Julian Barbour

In regard to The Adjacent Possible I was well aware of the implication and parameters  around such thinking to realize that even while applying the trade,  Stuart, was traveling new ground. His thinking is encouraging the flexibility that I am talking about with regard the restrictions one places on them self. I encourage this kind of thinking so as to bolster the lull in scientific advancement to stimulate and foster the idealization of creativity that I think has become stagnate while  moving from one point in the measure to the next. Why Murray Gell-Mann's  move and his expertise is understood in context of new approaches. Simplicity and complexity.

Setting Time Aright

See Also:

Thursday, September 01, 2011

Setting Time Aright

Time has no independent existence apart from the order of events by which we measure it.Albert Einstein

While Event has since past, I hope the lecture itself will remain in public domain. It helps so as to see the context of the discussion provided by this conference with regard to that subject of time.

Video streaming by Ustream

See:Setting Time Aright

In 1952, in his book Relativity, Einstein writes:

Since there exists in this four dimensional structure [space-time] no longer any sections which represent "now" objectively, the concepts of happening and becoming are indeed not completely suspended, but yet complicated. It appears therefore more natural to think of physical reality as a four dimensional existence, instead of, as hitherto, the evolution of a three dimensional existence

Setting Time Aright
View more presentations from Sean Carroll


  If man thinks of the totality as constituted of independent fragments, then that is how his mind will tend to operate, but if he can include everything coherently and harmoniously in an overall whole that is undivided, unbroken, and without a border then his mind will tend to move in a similar way, and from this will flow an orderly action within the whole. (David Bohm, Wholeness and the Implicate Order, 1980)

Lee Smolin:
I suspect this reflects the expectation many people have that time is not fundamental, but rather emerges only at a semiclassical approximation in quantum cosmology. If you believe this then you believe that the fundamental quantities a quantum cosmology should compute are timeless. This in turn reflects a very old and ultimately religious prejudice that deeper truths are timeless. This has been traced by scholars to the theology of Newton and contemporaries who saw space as “the sensorium” of an eternal and all seeing god. Perhaps the BB paradox is telling us it is time to give up the search for timeless probability distributions, and recognize that since Darwin the deep truths about nature cannot be divorced from time.

The alternative is to disbelieve the arguments that time is emergent-which were never very convincing- and instead formulate quantum cosmology in such a way that time is always real. I would suggest that the Boltzman Brain’s paradox is the reducto ad absurdum of the notion that time is emergent and that rather than play with little fixes to it we should try to take seriously the opposite idea: that time is real.


Bar of Lead Tungstate Source: A Quantum Diaries Survivor-Calorimeters for High Energy Physics experiments - part 1 April 6, 2008
Calorimeters measure the collective behavior of particles traveling along approximately the same path, and are thus naturally suited for the measurement of jets-Dorigo Tommaso


Tuesday, February 16, 2010

Article From New York Times and More

Brookhaven National Laboratory

HOT A computer rendition of 4-trillion-degree Celsius quark-gluon plasma created in a demonstration of what scientists suspect shaped cosmic history.

In Brookhaven Collider, Scientists Briefly Break a Law of Nature

The Brookhaven scientists and their colleagues discussed their latest results from RHIC in talks and a news conference at a meeting of the American Physical Society Monday in Washington, and in a pair of papers submitted to Physical Review Letters. “This is a view of what the world was like at 2 microseconds,” said Jack Sandweiss of Yale, a member of the Brookhaven team, calling it, “a seething cauldron.”

Among other things, the group announced it had succeeded in measuring the temperature of the quark-gluon plasma as 4 trillion degrees Celsius, “by far the hottest matter ever made,” Dr. Vigdor said. That is 250,000 times hotter than the center of the Sun and well above the temperature at which theorists calculate that protons and neutrons should melt, but the quark-gluon plasma does not act the way theorists had predicted.

Instead of behaving like a perfect gas, in which every quark goes its own way independent of the others, the plasma seemed to act like a liquid. “It was a very big surprise,” Dr. Vigdor said, when it was discovered in 2005. Since then, however, theorists have revisited their calculations and found that the quark soup can be either a liquid or a gas, depending on the temperature, he explained. “This is not your father’s quark-gluon plasma,” said Barbara V. Jacak, of the State University at Stony Brook, speaking for the team that made the new measurements.

It is now thought that the plasma would have to be a million times more energetic to become a perfect gas. That is beyond the reach of any conceivable laboratory experiment, but the experiments colliding lead nuclei in the Large Hadron Collider outside Geneva next winter should reach energies high enough to see some evolution from a liquid to a gas.
See more at above link.


Violating Parity with Quarks and Gluons
by Sean Carroll of Cosmic Variance
This new result from RHIC doesn’t change that state of affairs, but shows how quarks and gluons can violate parity spontaneously if they are in the right environment — namely, a hot plasma with a magnetic field.

So, okay, no new laws of physics. Just a much better understanding of how the existing ones work! Which is most of what science does, after all


Quark–gluon plasma

From Wikipedia, the free encyclopedia

A QGP is formed at the collision point of two relativistically accelerated gold ions in the center of the STAR detector at the relativistic heavy ion collider at the Brookhaven national laboratory.

A quark-gluon plasma (QGP) or quark soup[1] is a phase of quantum chromodynamics (QCD) which exists at extremely high temperature and/or density. This phase consists of (almost) free quarks and gluons, which are the basic building blocks of matter. Experiments at CERN's Super Proton Synchrotron (SPS) first tried to create the QGP in the 1980s and 1990s: the results led CERN to announce indirect evidence for a "new state of matter"[2] in 2000. Current experiments at Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) are continuing this effort.[3] Three new experiments running on CERN's Large Hadron Collider (LHC), ALICE,[4] ATLAS and CMS, will continue studying properties of QGP.


  • 1 General introduction

    • 1.1 Why this is referred to as "plasma"
    • 1.2 How the QGP is studied theoretically
    • 1.3 How it is created in the lab
    • 1.4 How the QGP fits into the general scheme of physics
  • 2 Expected properties

    • 2.1 Thermodynamics
    • 2.2 Flow
    • 2.3 Excitation spectrum
  • 3 Experimental situation
  • 4 Formation of quark matter
  • 5 See also
  • 6 References
  • 7 External links

General introduction

The quark-gluon plasma contains quarks and gluons, just as normal (baryonic) matter does. The difference between these two phases of QCD is that in normal matter each quark either pairs up with an anti-quark to form a meson or joins with two other quarks to form a baryon (such as the proton and the neutron). In the QGP, by contrast, these mesons and baryons lose their identities and dissolve into a fluid of quarks and gluons.[5] In normal matter quarks are confined; in the QGP quarks are deconfined.
Although the experimental high temperatures and densities predicted as producing a quark-gluon plasma have been realized in the laboratory, the resulting matter does not behave as a quasi-ideal state of free quarks and gluons, but, rather, as an almost perfect dense fluid.[6] Actually the fact that the quark-gluon plasma will not yet be "free" at temperatures realized at present accelerators had been predicted already in 1984 [7] as a consequence of the remnant effects of confinement. 

Why this is referred to as "plasma"

A plasma is matter in which charges are screened due to the presence of other mobile charges; for example: Coulomb's Law is modified to yield a distance-dependent charge. In a QGP, the color charge of the quarks and gluons is screened. The QGP has other analogies with a normal plasma. There are also dissimilarities because the color charge is non-abelian, whereas the electric charge is abelian. Outside a finite volume of QGP the color electric field is not screened, so that volume of QGP must still be color-neutral. It will therefore, like a nucleus, have integer electric charge.

How the QGP is studied theoretically

One consequence of this difference is that the color charge is too large for perturbative computations which are the mainstay of QED. As a result, the main theoretical tools to explore the theory of the QGP is lattice gauge theory. The transition temperature (approximately 175 MeV) was first predicted by lattice gauge theory. Since then lattice gauge theory has been used to predict many other properties of this kind of matter. The AdS/CFT correspondence is a new interesting conjecture allowing insights in QGP.

How it is created in the lab

The QGP can be created by heating matter up to a temperature of 2×1012 kelvin, which amounts to 175 MeV per particle. This can be accomplished by colliding two large nuclei at high energy (note that 175 MeV is not the energy of the colliding beam). Lead and gold nuclei have been used for such collisions at CERN SPS and BNL RHIC, respectively. The nuclei are accelerated to ultrarelativistic speeds and slammed into each other while Lorentz contracted. They largely pass through each other, but a resulting hot volume called a fireball is created after the collision. Once created, this fireball is expected to expand under its own pressure, and cool while expanding. By carefully studying this flow, experimentalists hope to put the theory to test.

How the QGP fits into the general scheme of physics

QCD is one part of the modern theory of particle physics called the Standard Model. Other parts of this theory deal with electroweak interactions and neutrinos. The theory of electrodynamics has been tested and found correct to a few parts in a trillion. The theory of weak interactions has been tested and found correct to a few parts in a thousand. Perturbative aspects of QCD have been tested to a few percent. In contrast, non-perturbative aspects of QCD have barely been tested. The study of the QGP is part of this effort to consolidate the grand theory of particle physics.
The study of the QGP is also a testing ground for finite temperature field theory, a branch of theoretical physics which seeks to understand particle physics under conditions of high temperature. Such studies are important to understand the early evolution of our universe: the first hundred microseconds or so. While this may seem esoteric, this is crucial to the physics goals of a new generation of observations of the universe (WMAP and its successors). It is also of relevance to Grand Unification Theories or 'GUTS' which seek to unify the four fundamental forces of nature.

Expected properties


The cross-over temperature from the normal hadronic to the QGP phase is about 175 MeV, corresponding to an energy density of a little less than 1 GeV/fm3. For relativistic matter, pressure and temperature are not independent variables, so the equation of state is a relation between the energy density and the pressure. This has been found through lattice computations, and compared to both perturbation theory and string theory. This is still a matter of active research. Response functions such as the specific heat and various quark number susceptibilities are currently being computed.


The equation of state is an important input into the flow equations. The speed of sound is currently under investigation in lattice computations. The mean free path of quarks and gluons has been computed using perturbation theory as well as string theory. Lattice computations have been slower here, although the first computations of transport coefficients have recently been concluded. These indicate that the mean free time of quarks and gluons in the QGP may be comparable to the average interparticle spacing: hence the QGP is a liquid as far as its flow properties go. This is very much an active field of research, and these conclusions may evolve rapidly. The incorporation of dissipative phenomena into hydrodynamics is another recent development that is still in an active stage.

Excitation spectrum

Does the QGP really contain (almost) free quarks and gluons? The study of thermodynamic and flow properties would indicate that this is an over-simplification. Many ideas are currently being evolved and will be put to test in the near future. It has been hypothesized recently that some mesons built from heavy quarks (such as the charm quark) do not dissolve until the temperature reaches about 350 MeV. This has led to speculation that many other kinds of bound states may exist in the plasma. Some static properties of the plasma (similar to the Debye screening length) constrain the excitation spectrum.

Experimental situation

Those aspects of the QGP which are easiest to compute are not the ones which are the easiest to probe in experiments. While the balance of evidence points towards the QGP being the origin of the detailed properties of the fireball produced in the RHIC, this is the main barrier which prevents experimentalists from declaring a sighting of the QGP. For a summary see 2005 RHIC Assessment.
The important classes of experimental observations are

Formation of quark matter

In April 2005, formation of quark matter was tentatively confirmed by results obtained at Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC). The consensus of the four RHIC research groups was that they had created a quark-gluon liquid of very low viscosity. However, contrary to what was at that time still the widespread assumption, it is yet unknown from theoretical predictions whether the QCD "plasma", especially close to the transition temperature, should behave like a gas or liquid[8]. Authors favoring the weakly interacting interpretation derive their assumptions from the lattice QCD calculation, where the entropy density of quark-gluon plasma approaches the weakly interacting limit. However, since both energy density and correlation shows significant deviation from the weakly interacting limit, it has been pointed out by many authors that there is in fact no reason to assume a QCD "plasma" close to the transition point should be weakly interacting, like electromagnetic plasma (see, e.g., [9]).

See also


External links

Tuesday, August 05, 2008

Memories Arise Out of a Equilibrium

Sean Carroll of Cosmic Variance, California Institute of Technology and David Albert-Columbia University
Science Saturday: Time’s Arrow

Some highlights at different spots of the exchange.

  • How a philosopher of science spends his time (08:34)

  • David describes his run-in with the “What the Bleep!?” cultists (11:56)

  • Is good science too disturbing to make good entertainment? (04:46)

  • Sean and David take on John Horgan’s critique of string theory (10:54)

  • String theory’s predictive power (or lack thereof) (06:04)

  • Why is the past so different, in so many ways, from the future? (12:20)

  • I selected the title for a reason. I will have to go back and record the exact time of this comment as it arises. Time 53:48 David mentions the point about a memory forming out of a equilibrium which not only encompasses the future, but can also include the past.

    The integration of a philosophy of science alongside of a person in theoretics seems like a good idea to me. There is something to be said about this language used even though used in the conceptual performance of this collaboration.

    Now you must know, that I speak from a position of one that is of discovery about the nature of the mathematics, as I have come to understand it. Yes sure I may cloud the interpretation of the mathematical deduction with the idea of a regress to an ultimate position in mind, that we might compare such relations to what the cosmos is saying and what we are saying about the future and past.

    I will not discount the very fabric such psychologies might go too, to develop concept maps themselves, to map the thinking being as to the regress of reason, and it's ultimate fate resting in such a mathematical description.

    When I point out the relation to WMAP and the idea of this mathematical relationship, one might see the underlying method with which Sean and David intermingle conceptually. To bring forward a clear and consistent description of what begins and ends in the universe, might mean in relation to the past and future. What it means in relation to the memory that arises

    I am looking to define such a shape as well as to the very nature of this universe.

    Incompatible Arrows

    I link the previous blog entry above for consideration, in line with the topic of this post, so that the "continuance of this position" describes the other half of the talking heads, that Sean Carroll represents.

    Sean Carroll has a interesting set of four entires about the backwardness of the arrow of time and how it would appear. This is an interesting exercise for me on how perception about the current direction of the universe could have represented "the Egg before the chicken" scenarios.

    Incompatible Arrows, I: Martin Amis
    Incompatible Arrows, II: Kurt Vonnegut
    Incompatible Arrows, III: Lewis Carroll
    Incompatible Arrows, IV: F. Scott Fitzgerald

    Chicken or Egg

    Illustration from Tacuina sanitatis, Fourteenth century

    Reverse chronologynarrating a story, or parts of one, backwards in time — is a venerable technique in literature, going back at least as far as Virgil’s Aeneid. Much more interesting is a story with incompatible arrows of time: some characters live “backwards” while others experience life normally.


    One should be aware that there are a series of bloggingheads up and coming that are being exchanged here.

    Sean Carroll
    This raises all sorts of questions, the most basic of which are: “What counts as `looking’ vs. `not looking’?” and “Do we really need a separate law of physics to describe the evolution of systems that are being looked at?”
    See:Quantum Diavlog

    Sunday, April 06, 2008

    Incompatible Arrows

    Commerce is of trivial import; love, faith, truth of character, the aspiration of man, these are sacred.Ralph Waldo Emerson

    I just happen to visit Cosmic Variance yesterday after not visiting for some time. The timing seemed appropriate to my questions about our histories, not only from a detailed research perspective, but from a personal one as well in terms of our memories. I do not care who is an atheist or not. Why should I apply a stereotype to another person and dictate the way the conversation can go?:)

    Sean Carroll has a interesting set of four entires about the backwardness of the arrow of time and how it would appear. This is an interesting exercise for me on how perception about the current direction of the universe could have represented "the Egg before the chicken" scenarios.

    Incompatible Arrows, I: Martin Amis
    Incompatible Arrows, II: Kurt Vonnegut
    Incompatible Arrows, III: Lewis Carroll
    Incompatible Arrows, IV: F. Scott Fitzgerald

    Chicken or Egg

    Illustration from Tacuina sanitatis, Fourteenth century

    Reverse chronologynarrating a story, or parts of one, backwards in time — is a venerable technique in literature, going back at least as far as Virgil’s Aeneid. Much more interesting is a story with incompatible arrows of time: some characters live “backwards” while others experience life normally.

    There are reasons why I find this fascinating and why the topic of Kurt Godel was introduced in that comment section. It is something that caught my eye while researching Kurt Godel. I will try and find this point and put it here for consideration. While considering the version I saw of his authored biographical comment, it made me think of the views people "can have" about the nonsensical. The feelings they can have about the "incompleteness of this life" and the succession of our views on this life as a "metamathematical position." Where is that? Some "OverSoul" perhaps?:)

    It reminded me about the perspective we can have "from the here and now."

    Mind Body problem

    Proud atheists

    Steve Paulson:I know neither of you believes in paranormal experiences like telepathy or clairvoyant dreams or contact with the dead. But hypothetically, suppose even one of these experiences were proven beyond a doubt to be real. Would the materialist position on the mind-brain question collapse in a single stroke?

    PINKER: Yeah.

    GOLDSTEIN: Yeah, if there was no other explanation. We'd need to have such clear evidence. I have to tell you, I've had some uncanny experiences. Once, in fact, I had a very strange experience where I seemed to be getting information from a dead person. I racked my brain trying to figure out how this could be happening. I did come up with an explanation for how I could reason this away. But it was a very powerful experience. If it could truly be demonstrated that there was more to a human being than the physical body, this would have tremendous implications.

    While I had read your link Phil on Goldstein, I am not an atheist(I try and refrain from groupings) in any form, and, like the topics of "Intelligent design" or the Anthropic principle, this has no bearing on how I want to move and think in the world. I am convinced, as Goldstein was, on what is consider "proof of the afterlife" that I do not need to be reminded of what is evidenced to the contrary, until it is proofed conclusively.

    "Death, so called, is but older matter dressed
    In some new form. And in a varied vest,
    From tenement to tenement though tossed,
    The soul is still the same, the figure only lost."
    Poem on Pythagoras, Dryden's Ovid.

    I may share a trait of Plato eh?:)Emerson? Benjamin Franklin?

    From A Defense of an Essay of Dramatic Poesy (1668) by John Dryden

    Imagination in a man, or reasonable creature, is supposed to participate of reason, and when that governs, as it does in the belief of fiction, reason is not destroyed, but misled, or blinded: that can prescribe tot he reason, during the time of the representation, somewhat like a weak belief of what it sees and hears; and reason suffers itself to be so hoodwinked, that it may better enjoy the pleasures of the fiction: but it is never so wholly made a captive as to be drawn headlong into a persuasion of those things which are most remote from probability: 'tis in that case a free-born subject, not a slave; it will contribute willingly its assent, as far as it sees convenient, but will not be forced....Fancy and reason go hand in hand; the first cannot leave the last behind; and though fancy, when it sees the wide gulf, would venture over, as the nimbler; yet it is withheld by reason, which will refuse to take the leap, when the distance over it appears too large


    The Universal Library

    Tuesday, January 15, 2008

    Boltzmann's Brain

    There is a new article by Dennis Overbye in the New York Times called, Big Brain Theory: Have Cosmologists Lost Theirs?

    It could be the weirdest and most embarrassing prediction in the history of cosmology, if not science.

    If true, it would mean that you yourself reading this article are more likely to be some momentary fluctuation in a field of matter and energy out in space than a person with a real past born through billions of years of evolution in an orderly star-spangled cosmos. Your memories and the world you think you see around you are illusions.

    Source: Sean Carroll, California Institute of Technology

    Alway part of the process is to find within my own site information that I had collected to help me understand where Ludwig Boltzmann comes into the picture in the above article.

    Now of course I go over to Cosmic Variance's version of Boltzmann's Universe where the article above is referred too.

    I look at the discussion that is taking place and try and put the exchange and points raised in mind so that I can understand as best I can "the jest" of the problem and the jest of what people are saying.

    This isn't an attempt to rewrite the article, but to open the door to a better understanding of what is being portrayed.

    Sean:lylebot, this is basically the point of the post — if the universe is a fluctuation around thermal equilibrium, then no matter what you condition on concerning our present state (including literally everything we know about it), it is overwhelmingly likely that it is a random fluctuation from a higher-entropy past. Even if we have memories apparently to the contrary!

    The Universe and Irreversibility

    Now it is quite loosely put together in my head that I went searching to try and understand the context in which the universe was placed in accordance to the state of equilibrium.

    In equilibrium, the entropy of the system cannot increase (because it is already at a maximum) and it cannot decrease (because that would violate the second law of thermodynamics). The only changes allowed are those in which the entropy remains constant.

    See: What is the entropy of the universe?

    Friday, December 21, 2007

    Bullet Cluster

    A purple haze shows dark matter flanking the "Bullet Cluster." Image Credit: X-ray: NASA/CXC/M.Markevitch et al. Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al. Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al

    The amount of matter, or "mass," in a galaxy is made up mostly of the gas that surrounds it. Stars, planets, moons and other objects count too, but a majority of the mass still comes from the hot, glowing clouds of hydrogen and other gases.

    When the Bullet Cluster's galaxies crossed and merged together, their stars easily continued on their way unscathed. This may seem a bit perplexing, because the bright light of stars makes them appear enormous and crowded together. It would be easy to expect them to smash into each other during their cosmic commute. But the truth is, stars are actually spaced widely apart and pass harmlessly like ships on an ocean.

    The gas clouds from the merging galaxies, however, found the going much tougher. As the clouds ran together, the rubbing and bumping of their gas molecules caused friction to develop. The friction slowed the clouds down, while the stars they contained kept right on moving. Before long, the galaxies slipped out of the gas clouds and into clear space.

    With the galaxies in open space, Chandra scientists found dark matter hiding.

    We can make certain conclusion about our universe given some insight into the geometric way our universe as a whole exists now?

    Lets first look at what Sean Carroll has to say and then we can go from here.

    The Cosmological Constant

    Sean M. Carroll
    Enrico Fermi Institute and Department of Physics
    University of Chicago
    5640 S. Ellis Ave.
    Chicago, IL 60637, U.S.A.


    This is a review of the physics and cosmology of the cosmological constant. Focusing on recent developments, I present a pedagogical overview of cosmology in the presence of a cosmological constant, observational constraints on its magnitude, and the physics of a small (and potentially nonzero) vacuum energy.

    What better way to speak to the content of the universe if you cannot look at the way it is now. It's current "geometric implication" as a result of the parameters we have deduced with WMAP, and resulting information on the content of the dark matter/energy within the universe?

    See:The Cosmological Parameters

    Sunday, November 04, 2007

    Dark Matter Issue

    We’re faced with the same choices today, with galaxies and clusters playing the role of the Solar System. Except that the question has basically been answered, by observations such as the Bullet Cluster. If you modify gravity, it’s fairly straightforward (although harder than you might guess, if you’re careful about it) to change the strength of gravity as a function of distance. So you can mock up “dark matter” by imagining that gravity at very large distances is just a bit stronger than Newton (or Einstein) would have predicted — as long as the hypothetical dark matter is in the same place as the ordinary matter is.

    In Dark Matter Still Existing, Sean Carroll of Cosmic Variance lays the topic out for readers to understand his position on this issue.

    An intergalactic collision is providing astronomers with a giant payoff: the first direct evidence of the invisible material that theorists say holds galaxies together and accounts for most of the universe's mass.

    CRASH COURSE. This composite image from several observatories and telescopes shows where two clusters of galaxies collided 100 million years ago. The ordinary matter, shown in pink, from the two galaxies collided, whereas the dark matter from each galaxy, shown in purple, passed straight through.
    Markevitch, et al., Clowe, et al., Magellan, Univ. of Arizona, CXC, CfA, STScI, ESO WFI, NASA

    What is Dark Matter? How Can We Make It in the LaboratoryConclusions
    Particle physics is in the midst of a great revolution. Modern data and ideas have challenged long-held beliefs about matter, energy, space and time. Observations have confirmed that 95 percent of the universe is made of dark energy and dark matter unlike any we have seen or touched in our most advanced experiments. Theorists have found a way to reconcile gravity with quantum physics, but at the price of postulating extra dimensions beyond the familiar four dimensions of space and time. As the magnitude of the current revolution becomes apparent, the science of particle physics has a clear path forward. The new data and ideas have not only challenged the old ways of thinking, they have also pointed to the steps required to make progress. Many advances are within reach of our current program; others are close at hand. We are extraordinarily fortunate to live in a time when the great questions are yielding a whole new level of understanding. We should seize the moment and embrace the challenges.

    See:What is Dark Matter/Energy?

    Monday, February 14, 2005

    The Arrow of Time

    Rudolf Julius Emanuel Clausius

    There is but one kind of entropy change. Entropy change is due to energy dispersal to, from, or within a system (as a function of temperature.), measured by microstate change: S = kB ln [microstates final / microstates initial ].

    I should back up here and mentioned that Peter Woit seems to be coming out in the open and explaining somethings that have been not so clear before?

    Perter Woit:
    Penrose also carefully lays out areas in which his point of view differs from the general consensus of most theoretical physicists. An example is his emphasis on the importance for cosmology of understanding why the universe had such low entropy at the Big Bang

    What is strange today that with this thought on the subject of entropy.

    Lubos Motl:
    This is what allows the early gas to clump (and seemingly create a more order state) without violating the 2nd law of thermodynamics: the gravitational entropy overcomensates the decrease of the entropy.

    OK, so why was the beginning of the Universe a low-entropy state? The best explanation we have is inflation. It simply explodes the size of the Universe. During inflation, the total entropy of the Universe grows, but much more slowly than how it would grow otherwise, without inflation

    if one did not understand the early universe consideration here, and the idealization of supersymmetry, could we have found a association to low orders of entropy since this early time would have been very topologically considered and part of a continuum?

    Entropy and the second law of thermodynamics

    Entropy is no mystery or complicated idea. Entropy is merely the way to measure the energy that spreads out in a process (as a function of temperature). What's complicated about that? Entropy change, S, measures how much energy is spread out in a system, or how spread out is the energy of a system (both always involving T). The first example in our text was melting ice to water at 273 K where S = q/T. So, in that equation, it's easy to see that q (the enthalpy of fusion) is how much "heat" energy was spread out in the ice to change it to water. What's the big deal?

    Update: Reading Peter Woit's blog today he linked Sean Carroll's "Arrow of Time article," so I thought it most apropriate to link it from here as well, since I am on the topic.

    Sean Carroll:
    Jennie and I do the following thought experiment -- if it weren't for inflation, what would be a "natural" state for the universe to be in? Different people have addressed this question, with different answers; Roger Penrose, for example, has suggested that it would be a lumpy universe full of black holes. Our answer is almost exactly the opposite -- the only natural state is empty space. This is basically because gravity makes everything unstable, and the entropy of any given configuration can always be increased by just expanding the universe by a huge factor. Sure, black holes will form, but they will ultimately evaporate away. If you let the universe evolve forever, it will ultimately get emptier and emptier (generically).