VACUUM STABILITY

AND

NEW PHYSICS

Emanuele Messina

University of Catania

INFN Sez. di Catania

INTERNATIONAL SCHOOL OF SUBNUCLEAR PHYSICS 53° Course: THE FUTURE OF OUR PHYSICS INCLUDING NEW FRONTIERS

Erice, 24 June – 3 July 2015

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References:

V. Branchina, E. Messina, Phys. Rev. Lett. 111, 241801 (2013) (arXiv:1307.5193);

V. Branchina, arXiv:1405.7864, Moriond 2014;

V. Branchina, E. Messina, A. Platania, JHEP 1409 (2014) 182 (arXiv:1407.4112);

V. Branchina, E. Messina, M. Sher, Phys. Rev.D91 (2015) 1, 013003 (arXiv:1408.5302);

V. Branchina, E. Messina, in preparation;

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The vacuum is unstable !!

INSTABILITY

SM interactions only

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CRITICAL CONDITION

STABLE

CRITICAL LINE

‘UNSTABLE’

(SM interactions only)

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EW EW EW

Planck Scale

new physics

MESTABILITY SCENARIO

METASTABLE

CRITICAL LINE

UNSTABLE (tout-court)

ASSUMPTION: NEW PHYSICS AT HIGH ENERGY SCALES CAN NOT HAVE AN IMPACT ON THE EW

VACUUM STABILITY.

STABILITY MESTABILITY

but

INSTABILITY

Buttazzo, Degrassi, Giardino, Giudice, Sala, Salvio, Strumia, JHEP 1312 (2013) 089.

STABILITY DIAGRAM

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(?)

NEGLECTING NEW PHYSICS…

Euclidean equation of motion with O(4) symmetry

BOUNCE SOLUTION FOR THE

CENTRAL VALUES…

COMPUTATION OF τ

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METASTABLE

NEGLECTING NEW PHYSICS…

Classical degeneracy

broken by quantum fluctuations

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A TOY UV COMPLETION High energy

couplings

Integrate out heavy d.o.f.

1 3

Impose threshold cond.

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THRESHOLD SCALE

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ADDING NEW PHYSICS (our approach)

SCALE INVARIANCE IS

BROKEN !!

NEW BOUNCE SOLUTION!!!!

DEPENDS ON THE

THRESHOLD SCALE

COMPUTATION OF τ

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UNSTABLE !!! (not universal)

Neglecting the effects of New

Physics ….

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To be compared with

Consider different Standard

Model extensions

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SUMMARY AND PERSPECTIVES

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THANK YOU

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Backup - Slides

IN FAVOR OF UNIVERSALITY

COMMON (AND INCORRECT) ARGUMENTS …

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BUT…

• QFT has an infinite number of d.o.f.

The Potential Energy is

• Vacuum - decay is a non-perturbative

phenomenon

ES. HIGGS DECAY

IS PERTURBATIVE

TUNNELING: NON - PERTURBATIVE

n. neighbour interactions

Tunneling in QFT like a

Nucleation process

FALSE

VACUUM TRUE

VACUUM

The transition

amplitude is

dominated by a non

local configuration

R

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WARNING 1: NEW PHYSICS IS NECESSARY (RESCUES THE POTENTIAL)

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