Gamma ray excess not from dark matter

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Gamma ray excess not from dark matter

#1  Postby newolder » May 03, 2017 6:15 pm

CHARACTERIZING THE POPULATION OF PULSARS IN THE GALACTIC BULGE WITH THE FERMI LARGE AREA TELESCOPE.

An excess of γ-ray emission from the Galactic Center (GC) region with respect to predictions based on a variety of interstellar emission models and γ-ray source catalogs has been found by many groups using data from the Fermi Large Area Telescope (LAT). Several interpretations of this excess have been invoked. In this paper we test the interpretation that the excess is caused by an unresolved population of γ-ray pulsars located in the Galactic bulge. We use cataloged LAT sources to derive criteria that efficiently select pulsars with very small contamination from blazars. We search for point sources in the inner 40◦ ×40◦ region of the Galaxy, derive a list of approximately 400 sources, and apply pulsar selection criteria to extract pulsar candidates among our source list. We also derive the efficiency of these selection criteria for γ-ray pulsars as a function of source energy flux and location. We demonstrate that given the observed spatial and flux distribution of pulsar candidates, a model that includes a population with about 2.7 γ-ray pulsars in the Galactic disk (in our 40◦ × 40◦ analysis region) for each pulsar in the Galactic bulge is preferred at the level of 7 standard deviations with respect to a disk-only model. The properties of these disk and bulge pulsar populations are consistent with the population of known γ-ray pulsars as well as with the spatial profile and energy spectrum of the GC excess. Finally, we show that the dark matter interpretation of the GC excess is strongly disfavored since a distribution of dark matter is not able to mimic the observed properties of the population of sources detected in our analysis.

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Re: Gamma ray excess not from dark matter

#2  Postby DavidMcC » May 10, 2017 12:52 pm

Hmm... perhaps dark matter really is dark at all photon energies, not just the visible. This would be the case if DM was a gravitational anomaly caused by a sister universe impinging on our dimensions, but very slightly separate in a fourth dimension, as I proposed in the LQG thread a few years ago.
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Re: Gamma ray excess not from dark matter

#3  Postby newolder » May 14, 2017 10:30 am

... but there could be(!?) a signal in cosmic ray energetics as measured by the Alpha Magentic Spectrometer (AMS-02) on the ISS:
One promising way to detect dark matter is to search for “excess” cosmic rays that presumably originate from dark matter (DM) particles annihilating each other in collisions. Two teams have separately analyzed recent data on cosmic-ray antiprotons obtained by the Alpha Magnetic Spectrometer (AMS) experiment. Both groups find indications of an excess of antiprotons that may correspond to a DM particle with a mass of several tens of GeV∕c2.

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Re: Gamma ray excess not from dark matter

#4  Postby DavidMcC » May 16, 2017 12:24 pm

It is certainly possible that there is more than one basic kind of dark matter. However, you seem to be implying that csomic rays account for most of the mass of the universe! That, I would find hard to swallow!
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Re: Gamma ray excess not from dark matter

#5  Postby newolder » May 16, 2017 1:53 pm

DavidMcC wrote:It is certainly possible that there is more than one basic kind of dark matter.

Yes.
However, you seem to be implying that csomic rays account for most of the mass of the universe!

Not at all. Prof. Ting (AMS-02 lead scientist) continues efforts to disprove the Randall-Sundrum (1999) model and its subsequent development.
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Re: Gamma ray excess not from dark matter

#6  Postby DavidMcC » May 16, 2017 2:43 pm

Randall and Sundrum's theory is the brane-world idea, that universes start in a manner akin to a bumper-to-bumper collision on a packed motorway (which is where they were when they came up with their model). It doesn't seem very natural to me! I much prefer the Lee Smolin idea that universes are black holes as seen from within their own space.
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Re: Gamma ray excess not from dark matter

#7  Postby newolder » May 16, 2017 4:35 pm

DavidMcC wrote:Randall and Sundrum's theory is the brane-world idea, that universes start in a manner akin to a bumper-to-bumper collision on a packed motorway (which is where they were when they came up with their model). It doesn't seem very natural to me! I much prefer the Lee Smolin idea that universes are black holes as seen from within their own space.

No. You need to (re-)read their paper, it's based on a model with 4 space + 1 time dimensions. (Whether the 4th space dimension is infinite in extent or bounded is part of the model's development in later work.)
We propose a new higher-dimensional mechanism for solving the Hierarchy Problem. The Weak scale is generated from a large scale of order the Planck scale through an exponential hierarchy. However, this exponential arises not from gauge interactions but from the background metric (which is a slice of AdS_5 spacetime). This mechanism relies on the existence of only a single additional dimension. We demonstrate a simple explicit example of this mechanism with two three-branes, one of which contains the Standard Model fields. The experimental consequences of this scenario are new and dramatic. There are fundamental spin-2 excitations with mass of weak scale order, which are coupled with weak scale as opposed to gravitational strength to the standard model particles. The phenomenology of these models is quite distinct from that of large extra dimension scenarios; none of the current constraints on theories with very large extra dimensions apply.

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Re: Gamma ray excess not from dark matter

#8  Postby DavidMcC » May 16, 2017 5:04 pm

newolder wrote:
DavidMcC wrote:Randall and Sundrum's theory is the brane-world idea, that universes start in a manner akin to a bumper-to-bumper collision on a packed motorway (which is where they were when they came up with their model). It doesn't seem very natural to me! I much prefer the Lee Smolin idea that universes are black holes as seen from within their own space.

No. You need to (re-)read their paper, it's based on a model with 4 space + 1 time dimensions. (Whether the 4th space dimension is infinite in extent or bounded is part of the model's development in later work.)
...

I was referring to their own words about how the idea came to them in a motorway traffic jam! Of course, they don't mention that in published papers, but certainly did in a TV interview - it was their words, not the journalist's.
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Re: Gamma ray excess not from dark matter

#9  Postby DavidMcC » May 16, 2017 5:07 pm

... The biggest problem is the total lack of evidence for the existence of branes, or collisions between them.
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Re: Gamma ray excess not from dark matter

#10  Postby newolder » May 16, 2017 5:11 pm

DavidMcC wrote:...
I was referring to their own words about how the idea came to them in a motorway traffic jam! Of course, they don't mention that in published papers, but certainly did in a TV interview - it was their words, not the journalist's.

The RS1 model is not concerned with universe creation.
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Re: Gamma ray excess not from dark matter

#11  Postby DavidMcC » May 16, 2017 5:50 pm

newolder wrote:
DavidMcC wrote:...
I was referring to their own words about how the idea came to them in a motorway traffic jam! Of course, they don't mention that in published papers, but certainly did in a TV interview - it was their words, not the journalist's.

The RS1 model is not concerned with universe creation.

So why did R&S talk about brane collisions causing big bangs?
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Re: Gamma ray excess not from dark matter

#12  Postby newolder » May 16, 2017 5:56 pm

DavidMcC wrote:
newolder wrote:
DavidMcC wrote:...
I was referring to their own words about how the idea came to them in a motorway traffic jam! Of course, they don't mention that in published papers, but certainly did in a TV interview - it was their words, not the journalist's.

The RS1 model is not concerned with universe creation.

So why did R&S talk about brane collisions causing big bangs?

Where did they do this? (Perhaps you are thinking of Paul Steinhardt & Neil Turok and their ekpyrotic model. :dunno:)
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Re: Gamma ray excess not from dark matter

#13  Postby DavidMcC » May 16, 2017 5:59 pm

newolder wrote:
DavidMcC wrote:
newolder wrote:
DavidMcC wrote:...
I was referring to their own words about how the idea came to them in a motorway traffic jam! Of course, they don't mention that in published papers, but certainly did in a TV interview - it was their words, not the journalist's.

The RS1 model is not concerned with universe creation.

So why did R&S talk about brane collisions causing big bangs?

Where did they do this? (Perhaps you are thinking of Paul Steinhardt & Neil Turok and their ekpyrotic model. :dunno:)

That's possible, but S&T also referred to branes in the TV interview.
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Re: Gamma ray excess not from dark matter

#14  Postby newolder » May 16, 2017 6:01 pm

DavidMcC wrote:
newolder wrote:
DavidMcC wrote:
newolder wrote:
The RS1 model is not concerned with universe creation.

So why did R&S talk about brane collisions causing big bangs?

Where did they do this? (Perhaps you are thinking of Paul Steinhardt & Neil Turok and their ekpyrotic model. :dunno:)

That's possible, but S&T also referred to branes in the TV interview.

You seem to be more confused than usual, today.
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Re: Gamma ray excess not from dark matter

#15  Postby DavidMcC » May 16, 2017 6:03 pm

... Ok, it all makes sense now!! R&S came up with a theory of space that didn't mention universe creation, then S&T try to add universe creation to it, so that it is more complete.
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Re: Gamma ray excess not from dark matter

#16  Postby DavidMcC » May 16, 2017 6:06 pm

newolder wrote:
DavidMcC wrote:
newolder wrote:
DavidMcC wrote:
So why did R&S talk about brane collisions causing big bangs?

Where did they do this? (Perhaps you are thinking of Paul Steinhardt & Neil Turok and their ekpyrotic model. :dunno:)

That's possible, but S&T also referred to branes in the TV interview.

You seem to be more confused than usual, today.

I admit only that it has been several years since I thought about half-baked cosmologies, and may have got names mixed up.
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Re: Gamma ray excess not from dark matter

#17  Postby newolder » May 16, 2017 6:07 pm

DavidMcC wrote:... Ok, it all makes sense now!! R&S came up with a theory of space that didn't mention universe creation, then S&T try to add universe creation to it, so that it is more complete.

The umbrella idea is known as M-theory. Anyhoo, the extra space dimension proposed certainly predates yours by some years:
DavidMcC wrote:...This would be the case if DM was a gravitational anomaly caused by a sister universe impinging on our dimensions, but very slightly separate in a fourth dimension, as I proposed in the LQG thread a few years ago.

... and both R&S and S&T make testable predictions.
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Re: Gamma ray excess not from dark matter

#18  Postby DavidMcC » May 16, 2017 6:15 pm

newolder wrote:
DavidMcC wrote:... Ok, it all makes sense now!! R&S came up with a theory of space that didn't mention universe creation, then S&T try to add universe creation to it, so that it is more complete.

The umbrella idea is known as M-theory. Anyhoo, the extra space dimension proposed certainly predates yours by some years:
DavidMcC wrote:...This would be the case if DM was a gravitational anomaly caused by a sister universe impinging on our dimensions, but very slightly separate in a fourth dimension, as I proposed in the LQG thread a few years ago.

... and both R&S and S&T make testable predictions.

I realise that they predate me, but that doesn't make then correct. Also, I haven't noticed any "testable predictions" being tested, in all the years since it was published.
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Re: Gamma ray excess not from dark matter

#19  Postby newolder » May 16, 2017 6:49 pm

DavidMcC wrote:
newolder wrote:
DavidMcC wrote:... Ok, it all makes sense now!! R&S came up with a theory of space that didn't mention universe creation, then S&T try to add universe creation to it, so that it is more complete.

The umbrella idea is known as M-theory. Anyhoo, the extra space dimension proposed certainly predates yours by some years:
DavidMcC wrote:...This would be the case if DM was a gravitational anomaly caused by a sister universe impinging on our dimensions, but very slightly separate in a fourth dimension, as I proposed in the LQG thread a few years ago.

... and both R&S and S&T make testable predictions.

I realise that they predate me, but that doesn't make then correct. Also, I haven't noticed any "testable predictions" being tested, in all the years since it was published.

They are rigorously tested and correct mathematical ideas. Whether they turn out to be correct models of our physics is still an open question - although Neil Turok seems to have moved onto newer, simpler ideas theses days at Perimeter...

How did you miss the B-mode spectrum in the CMBR? It's shape was a correct prediction in S&T's work - but the inflationary guys soon rebuilt their models to be indistinguishable - heigh ho.

And the AMS-02 results may yet turn out to have something to say on R&S's predictions of "Kaluza-Klein" particles.

That's how it works.
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Re: Gamma ray excess not from dark matter

#20  Postby DavidMcC » May 16, 2017 6:55 pm

newolder wrote:
newolder wrote:
DavidMcC wrote:
newolder wrote:
The umbrella idea is known as M-theory. Anyhoo, the extra space dimension proposed certainly predates yours by some years:

... and both R&S and S&T make testable predictions.

I realise that they predate me, but that doesn't make then correct. Also, I haven't noticed any "testable predictions" being tested, in all the years since it was published.

They are rigorously tested and correct mathematical ideas. Whether they turn out to be correct models of our physics is still an open question -...

That was my point - it's one thing to have good maths, but without evidence, it could be just fantasy in a mathematical form.
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