Alberto Nicolis
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View article: The connection between nonzero density and spontaneous symmetry breaking for interacting scalars
The connection between nonzero density and spontaneous symmetry breaking for interacting scalars Open
We consider U(1)-symmetric scalar quantum field theories at zero temperature. At nonzero charge densities, the ground state of these systems is usually assumed to be a superfluid phase, in which the global symmetry is spontaneously broken …
View article: S-matrix positivity without Lorentz invariance: a case study
S-matrix positivity without Lorentz invariance: a case study Open
A bstract We investigate the analytic structure of scattering amplitudes in theories in which Lorentz invariance is spontaneously broken. We do so by computing and studying the S-matrix for a simple example: a superfluid described by a com…
View article: Apparent fine tunings for field theories with broken space-time symmetries
Apparent fine tunings for field theories with broken space-time symmetries Open
We exhibit a class of effective field theories that have hierarchically small Wilson coefficients for operators that are not protected by symmetries but are not finely tuned. These theories possess bounded target spaces and vacua that brea…
View article: Apparently superluminal superfluids
Apparently superluminal superfluids Open
A bstract We consider the superfluid phase of a specific renormalizable relativistic quantum field theory. We prove that, within the regime of validity of perturbation theory and of the superfluid effective theory, there are consistent and…
View article: $S$-matrix positivity without Lorentz invariance: a case study
$S$-matrix positivity without Lorentz invariance: a case study Open
We investigate the analytic structure of scattering amplitudes in theories in which Lorentz invariance is spontaneously broken. We do so by computing and studying the S-matrix for a simple example: a superfluid described by a complex scala…
View article: The connection between nonzero density and spontaneous symmetry breaking for interacting scalars
The connection between nonzero density and spontaneous symmetry breaking for interacting scalars Open
A bstract We consider U(1)-symmetric scalar quantum field theories at zero temperature. At nonzero charge densities, the ground state of these systems is usually assumed to be a superfluid phase, in which the global symmetry is spontaneous…
View article: A technical analog of the cosmological constant problem and a solution thereof
A technical analog of the cosmological constant problem and a solution thereof Open
The near vanishing of the cosmological constant is one of the most puzzling open problems in theoretical physics. We consider a system, the so-called framid, that features a technically similar problem. Its stress-energy tensor has a Loren…
View article: Spontaneously broken boosts and the Goldstone continuum
Spontaneously broken boosts and the Goldstone continuum Open
The spontaneous breaking of boost invariance is ubiquitous in nature, yet the associated Goldstone bosons are nowhere to be seen. We discuss why some subtleties are to be expected in the Goldstone phenomenon for spontaneously broken boosts…
View article: Conformal solids and holography
Conformal solids and holography Open
We argue that a SO(d) magnetic monopole in an asymptotically AdS space-time is dual to a d-dimensional strongly coupled system in a solid state. In light of this, it would be remiss of us not to dub such a field configuration solidon. In t…
View article: Cosmology as a weak gravitational field and the trans-Planckian problem
Cosmology as a weak gravitational field and the trans-Planckian problem Open
A bstract At momenta much higher than the Hubble scale, the cosmological expansion can be thought of as a weak gravitational field. We consider QFT in a particularly convenient set of coordinates that makes this manifest, so that, for thos…
View article: Apparently superluminal superfluids
Apparently superluminal superfluids Open
We consider the superfluid phase of a specific renormalizable relativistic quantum field theory. We prove that, within the regime of validity of perturbation theory and of the superfluid effective theory, there are consistent and regular v…
View article: Report on 2212.08976v1
Report on 2212.08976v1 Open
We exhibit a class of effective field theories that have hierarchically small Wilson coefficients for operators that are not protected by symmetries but are not finely tuned.These theories possess bounded target spaces and vacua that break…
View article: Report on 2212.08976v1
Report on 2212.08976v1 Open
We exhibit a class of effective field theories that have hierarchically small Wilson coefficients for operators that are not protected by symmetries but are not finely tuned.These theories possess bounded target spaces and vacua that break…
View article: Low-temperature thermal corrections to a superfluid's equation of state
Low-temperature thermal corrections to a superfluid's equation of state Open
Using effective field theory methods, we calculate the low-temperature phonon thermal partition function for a generic superfluid, thus providing the leading thermal corrections to a superfluid's equation of state, thermodynamic quantities…
View article: Apparent Fine Tunings for Field Theories with Broken Space-Time Symmetries
Apparent Fine Tunings for Field Theories with Broken Space-Time Symmetries Open
We exhibit a class of effective field theories that have hierarchically small Wilson coefficients for operators that are not protected by symmetries but are not finely tuned. These theories possess bounded target spaces and vacua that brea…
View article: Improved Noether’s theorem for spacetime symmetries
Improved Noether’s theorem for spacetime symmetries Open
We exploit an ambiguity somewhat hidden in Noether’s theorem to derive systematically, for relativistic field theories, the stress-energy tensor’s improvement terms that are associated with additional spacetime symmetries beyond translatio…
View article: Cosmology as a weak gravitational field and the trans-Planckian problem
Cosmology as a weak gravitational field and the trans-Planckian problem Open
At momenta much higher than the Hubble scale, the cosmological expansion can be thought of as a weak gravitational field. We consider QFT in a particularly convenient set of coordinates that makes this manifest, so that, for those high mom…
View article: Snowmass Theory Frontier: Effective Field Theory
Snowmass Theory Frontier: Effective Field Theory Open
We summarize recent progress in the development, application, and understanding of effective field theories and highlight promising directions for future research. This Report is prepared as the TF02 "Effective Field Theory" topical group …
View article: Rotating cosmologies: classical and quantum
Rotating cosmologies: classical and quantum Open
We revisit spatially flat, anisotropic cosmologies within the framework of mini-superspace. Putting special emphasis on the symmetries of the mini-superspace action and on the associated conservation laws, we unveil a new class of rotating…
View article: Rotating cosmologies: classical and quantum
Rotating cosmologies: classical and quantum Open
We revisit spatially flat, anisotropic cosmologies within the framework of mini-superspace. Putting special emphasis on the symmetries of the mini-superspace action and on the associated conservation laws, we unveil a new class of rotating…
View article: Snowmass White Paper: Effective Field Theories for Condensed Matter Systems
Snowmass White Paper: Effective Field Theories for Condensed Matter Systems Open
We review recent progress and a number of future directions for applications of effective field theory methods to condensed matter systems broadly defined. Our emphasis is on areas that have allowed a fertile exchange of ideas between high…
View article: An improved Noether's theorem for spacetime symmetries
An improved Noether's theorem for spacetime symmetries Open
We exploit an ambiguity somewhat hidden in Noether's theorem to derive systematically, for relativistic field theories, the stress-energy tensor's improvement terms that are associated with additional spacetime symmetries beyond translatio…
View article: Lorentz from Galilei, deductively
Lorentz from Galilei, deductively Open
I argue that in the Lagrangian formulation of standard, Galilei-invariant Newtonian mechanics there are subtle but concrete signs of {\em Lorentz} invariance. In fact, in a specific sense made explicit in the paper, Newtonian mechanics is …
View article: Gravitational Mass Carried by Sound Waves
Gravitational Mass Carried by Sound Waves Open
We show that the commonly accepted statement that sound waves do not transport mass is only true at linear order. Using effective field theory techniques, we confirm the result found by Nicolis and Penco [Phys. Rev. B 97, 134516 (2018)PRBM…
View article: The mass of sound
The mass of sound Open
We show that the commonly accepted statement that sound waves do not transport mass is only true at linear order. Using effective field theory techniques, we confirm the result found in [1] for zero-temperature superfluids, and extend it t…
View article: Anisotropic tensor modes from icosahedral inflation
Anisotropic tensor modes from icosahedral inflation Open
For icosahedral inflation, we compute the tensor modes' two-point function in the presence of higher derivative corrections, and show that in general this features anisotropies that are aligned with the underlying icosahedral structure. Th…
View article: Mutual interactions of phonons, rotons, and gravity
Mutual interactions of phonons, rotons, and gravity Open
We introduce an effective point-particle action for generic particles living\nin a zero-temperature superfluid. This action describes the motion of the\nparticles in the medium at equilibrium as well as their couplings to sound\nwaves and …