35 research outputs found

### Asymptotic Symmetries, Holography and Topological Hair

Asymptotic symmetries of AdS$_4$ quantum gravity and gauge theory are derived
by coupling the dual CFT$_3$ to Chern-Simons gauge theory and 3D gravity in a
"probe" large-level limit. The infinite-dimensional symmetries are shown to
arise when one is restricted to boundary subspaces with effectively
two-dimensional geometry. A canonical example of such a restriction occurs
within the 4D subregion described by a Wheeler-DeWitt wavefunctional of AdS$_4$
quantum gravity. An AdS$_4$ analog of Minkowski "super-rotation" asymptotic
symmetry is probed by 3D Einstein gravity, yielding CFT$_2$ structure, via
AdS$_3$ foliation of AdS$_4$ and the AdS$_3$/CFT$_2$ correspondence. The
maximal asymptotic symmetry is however probed by 3D conformal gravity. Both 3D
gravities have Chern-Simons formulation, manifesting their topological
character. Chern-Simons structure is also shown to be emergent in the Poincare
patch of AdS$_4$, as soft/boundary limits of 4D gauge theory, rather than "put
in by hand", with a finite effective Chern-Simons level. Several of the
considerations of asymptotic symmetry structure are found to be simpler for
AdS$_4$ than for Mink$_4$, such as non-zero 4D particle masses, 4D
non-perturbative "hard" effects, and consistency with unitarity. The last of
these, in particular, is greatly simplified, because in some set-ups the time
dimension is explicitly shared by each level of description: Lorentzian
AdS$_4$, CFT$_3$ and CFT$_2$. The CFT$_2$ structure clarifies the sense in
which the infinite asymptotic charges constitute a useful form of "hair" for
black holes and other complex 4D states. An AdS$_4$ (holographic) "shadow"
analog of Minkowski "memory" effects is derived. Lessons from AdS$_4$ provide
hints for better understanding Minkowski asymptotic symmetries, the 3D
structure of its soft limits, and Minkowski holography.Comment: typos corrected, references added, discussions of boundary conditions
corrected and clarifie

### Resonance at 125 GeV: Higgs or Dilaton/Radion?

We consider the possibility that the new particle that has been observed at
125 GeV is not the Standard Model (SM) Higgs, but instead the dilaton
associated with an approximate conformal symmetry that has been spontaneously
broken. We focus on dilatons that arise from theories of technicolor, or from
theories of the Higgs as a pseudo-Nambu-Goldstone boson (pNGB), that involve
strong conformal dynamics in the ultraviolet. In the pNGB case, we are
considering a framework where the Higgs particle is significantly heavier than
the dilaton and has therefore not yet been observed. In each of the technicolor
and pNGB scenarios, we study both the case when the SM fermions and gauge
bosons are elementary, and the case when they are composites of the strongly
interacting sector. Our analysis incorporates conformal symmetry violating
effects, which are necessarily present since the dilaton is not massless, and
is directly applicable to a broad class of models that stabilize the weak scale
and involve strong conformal dynamics. Since the AdS/CFT correspondence relates
the radion in Randall-Sundrum (RS) models to the dilaton, our results also
apply to RS models with the SM fields localized on the infrared brane, or in
the bulk. We identify the parameters that can be used to distinguish the
dilatons associated with the several different classes of theories being
considered from each other, and from the SM Higgs. We perform a fit to all the
available data from several experiments and highlight the key observations to
extract these parameters. We find that at present, both the technicolor and
pNGB dilaton scenarios provide a good fit to the data, comparable to the SM
Higgs. We indicate the future observations that will help to corroborate or
falsify each scenario.Comment: 41 pages, 4 figures. Analysis updated using current theoretical
limits on dimensions of CFT operators. References added. Version to appear on
JHE

### Phase Transition to RS: Cool, not Supercool

Motivated by the warped conifold compactification, we model the infrared (IR)
dynamics of confining gauge theories in a Randall-Sundrum (RS)-like setup by
modifying the stabilizing Goldberger-Wise (GW) potential so that it becomes
large (in magnitude) in the IR and back-reacts on the geometry. We study the
high-temperature phase by considering a black brane background in which we
calculate the entropy and free energy of the strongly back-reacted solution. As
with Buchel's result for the conifold (arXiv:2103.15188), we find a minimum
temperature beyond which the black brane phase is thermodynamically unstable.
In the context of a phase transition to the confining background, our results
suggest that the amount of supercooling that the metastable black brane phase
undergoes can be limited. It also suggests the first-order phase transition
(and the associated gravitational waves from bubble collision) is not
universal. Our results therefore have important phenomenological implications
for early universe model building in these scenarios.Comment: 39 pages, 13 figure

### Interactions of a Stabilized Radion and Duality

We determine the couplings of the graviscalar radion in Randall-Sundrum
models to Standard Model fields propagating in the bulk of the space, taking
into account effects arising from the dynamics of the Goldberger-Wise scalar
that stabilizes the size of the extra dimension. The leading corrections to the
radion couplings are shown to arise from direct contact interactions between
the Goldberger-Wise scalar and the Standard Model fields. We obtain a detailed
interpretation of the results in terms of the holographic dual of the radion,
the dilaton. In doing so, we determine how the familiar identification of the
parameters on the two sides of the AdS/CFT correspondence is modified in the
presence of couplings of the bulk Standard Model fields to the Goldberger-Wise
scalar. We find that corrections to the form of the dilaton couplings from
effects associated with the stabilization of the extra dimension are suppressed
by the square of the ratio of the dilaton mass to the Kaluza-Klein scale, in
good agreement with results from the CFT side of the correspondence.Comment: 22 pages plus appendices and reference

### Searching for Elusive Dark Sectors with Terrestrial and Celestial Observations

We consider the possible existence of a SM-neutral and light dark sector
coupled to the visible sector through irrelevant portal interactions. Scenarios
of this kind are motivated by dark matter and arise in various extensions of
the Standard Model. We characterize the dark dynamics in terms of one
ultraviolet scale $\Lambda_\text{UV}$, at which the exchange of heavy mediator
fields generates the portal operators, and by one infrared scale
$\Lambda_\text{IR}$, setting the mass gap. At energies $\Lambda_\text{IR} \ll E
\ll \Lambda_\text{UV}$ the dark sector behaves like a conformal field theory
and its phenomenology can be studied model independently. We derive the
constraints set on this scenario by high- and low-energy laboratory experiments
and by astrophysical observations. Our results are conservative and serve as a
minimum requirement that must be fulfilled by the broad class of models
satisfying our assumptions, of which we give several examples. The experimental
constraints are derived in a manner consistent with the validity of the
effective field theory used to define the portal interactions. We find that
high-energy colliders give the strongest bounds and exclude UV scales up to a
few TeV, but only in specific ranges of the IR scale. The picture emerging from
current searches can be taken as a starting point to design a future
experimental strategy with broader sensitivity.Comment: Typos fixed, some discussions improved, references added. Version
accepted in JHE