J.W. Ustron 2009

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UN

B. GrzadkowskiJ.W

- cosmology

J.W. Ustron 2009

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UVcompletion

Basic idea

New type of physics such that

• It is conformally invariant in the IR• Asymptotically free in the UV• It interacts weakly with the SM

Standard Standard ModelModel

Banks-Zaks (BZ) phase

Asymptotically free

Unparticle (U) phase

Conformally invariant

New New physicsphysics

HeavyMediators

J.W. Ustron 2009

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UV completion

BZ phase

Unparticle phase

The history of unparticles is dark and unknown but it is nevertheless divided by theoreticians into three periods

The first about which we know nothing

The second about which we know almost as much as about the first

And the third which succeeded the first two

(with apologies to A. Averchenko)

The new physics sector has two relevant scales:

J.W. Ustron 2009

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To make calculations one needs:

Rather unique collider signatures

No experimental motivation whatsoever

Can be used to understand how unusual types of new physics can affect cosmic evolution

That follows from conformal invariance

J.W. Ustron 2009

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Thermodynamics

Conformal invariance:

• has a non-trivial IR zero at g=g*

• The trace of the energy momentum tensor vanishes in the IR g

g*

g

g*

= anomalous dimension of F2

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) For available models gNP » 100

In the UV: asymptotically free ) / T4 to leading order

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SM-NP interactions Equilibrium, freeze-out and thaw-in

Standard approach: use the Boltzmann equation

Equilibrium as long as > H

= H at T = Tf

Less standard approach: use the Kubo equation … yields the same result … but does not need to introduce the unparticle distribution function

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NP

SM

SM’

NP’

Energy = ESM

4-momentum=KSM

Energy = ENP

4-momentum=KNP

Energy = E4 mom. = K

Energy = E’SM

4-momentum=K’SM

Energy = E’NP

4-momentum=K’NP

Energy = E’4 mom. = K’

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Only need a order of magnitude estimate for :

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dSM + dNP > 4.5 ) freeze-outdSM + dNP < 4.5 ) thaw-in

> H: coupled< H: decoupled' H ) T = Tf

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SN-NP coupling/decoupling

Blue: Tf 2 U phase

Red: SM-NP coupled

No-color: Tf < v

We assume that SP and NP were in equillibrium as T ! 1

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Unparticle effects on BBN

If SM-NP were in equilibrium and then decoupled, TSM and TNP can be related using entropy conservation:

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If SM-NP remain in equilibrium during BBN: gIR < 0.3

NP contribution to mimics that of additional ’s

So unparticle models should exhibit conformal invariance with a small number of RDF in the IR.

Unaware of an explicit model with this property

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Comments

Strongly coupled new physics can lead to /H » Tn (n positive or negative) ) A variety o freeze-out and thaw-in scenarios are viable ) BBN generates strong constraints on the NP.

Even for the “normal” decoupling scenarios (n>0) the BBN constraint is significant: gIR < 20, while the models available have gIR > 100

Unparticle models also suffer from potential theoretical problems: the coupling to the SM necessarily breaks conformal invariance.

If this effect is strong the above arguments do not apply … but then the experimental signatures are particle-like