arXiv subjects

Alexandria Costantino

Publications and source records attributed to Alexandria Costantino.

4 recordsLinked to original sources

arXiv2021

Effective Field Theory in AdS: Continuum Regime, Soft Bombs, and IR Emergence

We consider a scalar field in a slice of Lorentzian five-dimensional AdS at arbitrary energies. We show that the presence of bulk interactions separate the behavior of the theory into two different regimes: Kaluza--Klein and continuum. We determine the transition scale between these regimes and show that UV brane correlation functions are independent of IR brane-localized operators for four-momenta beyond this transition scale. The same bulk interactions that induce the transition also give rise to cascade decays. We study these cascade decays for the case of a cubic self-interaction in the continuum regime. We find that the cascade decay progresses slowly towards the IR region and gives rise to soft spherical final states, in accordance with former results from both gravity and CFT. We identify a recursion relation between integrated squared amplitudes of different leg numbers and thus evaluate the total rate. We find that cascade decays in the continuum regime are exponentially suppressed. This feature completes the picture of the IR brane as an emergent sector as seen from the UV brane. We briefly discuss consistency with the holographic dual description of glueballs and some implications for dark sector models.

hep-th↗

arXiv2021

Opacity from Loops in AdS

We investigate how quantum dynamics affects the propagation of a scalar field in Lorentzian AdS. We work in momentum space, in which the propagator admits two spectral representations (denoted "conformal" and "momentum") in addition to a closed-form one, and all have a simple split structure. Focusing on scalar bubbles, we compute the imaginary part of the self-energy $ {\rm Im} Π$ in the three representations, which involves the evaluation of seemingly very different objects. We explicitly prove their equivalence in any dimension, and derive some elementary and asymptotic properties of $ {\rm Im} Π$. Using a WKB-like approach in the timelike region, we evaluate the propagator dressed with the imaginary part of the self-energy. We find that the dressing from loops exponentially dampens the propagator when one of the endpoints is in the IR region, rendering this region opaque to propagation. This suppression may have implications for field-theoretical model-building in AdS. We argue that in the effective theory (EFT) paradigm, opacity of the IR region induced by higher dimensional operators censors the region of EFT breakdown. This confirms earlier expectations from the literature. Specializing to AdS$_5$, we determine a universal contribution to opacity from gravity.

hep-th↗

arXiv2020

The Neutrino Casimir Force

In the low energy effective theory of the weak interaction, a macroscopic force arises when pairs of neutrinos are exchanged. We calculate the neutrino Casimir force between plates, allowing for two different mass eigenstates within the loop. We also provide the general potential between point sources. We discuss the possibility of distinguishing whether neutrinos are Majorana or Dirac fermions using these quantum forces.

hep-ph↗

arXiv2020

Exotic Spin-Dependent Forces from a Hidden Sector

New dynamics from hidden sectors may manifest as long-range forces between visible matter particles. The well-known case of Yukawa-like potentials occurs via the exchange of a single virtual particle. However, more exotic behavior is also possible. We present three classes of exotic potentials that are generated by relativistic theories: (i) quantum forces from the loop-level exchange of two virtual particles, (ii) conformal forces from a conformal sector, and (iii) emergent forces from degrees of freedom that only exist in the infrared regime of the theory. We discuss the complementarity of spin-dependent force searches in an effective field theory framework. We identify well-motivated directions to search for exotic spin-dependent forces.

hep-ph↗