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Alfredo Iorio

Publications and source records attributed to Alfredo Iorio.

At least 55 records · Page 3Linked to original sources

Imaginary crystals made real

We realize Lobachevsky geometry in a simulation lab, by producing a carbon-based mechanically stable molecular structure, arranged in the shape of a Beltrami pseudosphere. We find that this structure: i) corresponds to a non-Euclidean crystallographic group, namely a loxodromic subgroup of SL(2,Z); ii) has an unavoidable singular boundary, that we fully take into account. Our approach, substantiated by extensive numerical simulations of Beltrami pseudospheres of different size, might be applied to other surfaces of constant negative Gaussian curvature, and points to a general procedure to generate them. Our results also pave the way to test certain scenarios of the physics of curved spacetimes.

cond-mat.mtrl-sci↗

Quantum field theory in curved graphene spacetimes, Lobachevsky geometry, Weyl symmetry, Hawking effect, and all that

The solutions of many issues, of the ongoing efforts to make deformed graphene a tabletop quantum field theory in curved spacetimes, are presented. A detailed explanation of the special features of curved spacetimes, originating from embedding portions of the Lobachevsky plane into $\mathbf{R}^3$, is given, and the special role of coordinates for the physical realizations in graphene, is explicitly shown, in general, and for various examples. The Rindler spacetime is reobtained, with new important differences with respect to earlier results. The de Sitter spacetime naturally emerges, for the first time, paving the way to future applications in cosmology. The role of the BTZ black hole is also briefly addressed. The singular boundary of the pseudospheres, "Hilbert horizon", is seen to be closely related to event horizon of the Rindler, de Sitter, and BTZ kind. This gives new, and stronger, arguments for the Hawking phenomenon to take place. An important geometric parameter, $c$, overlooked in earlier work, takes here its place for physical applications, and it is shown to be related to graphene's lattice spacing, $\ell$. It is shown that all surfaces of constant negative curvature, ${\cal K} = -r^{-2}$, are unified, in the limit $c/r \to 0$, where they are locally applicable to the Beltrami pseudosphere. This, and $c = \ell$, allow us a) to have a phenomenological control on the reaching of the horizon; b) to use spacetimes different than Rindler for the Hawking phenomenon; c) to approach the generic surface of the family. An improved expression for the thermal LDOS is obtained. A non-thermal term for the total LDOS is found. It takes into account: a) the peculiarities of the graphene-based Rindler spacetime; b) the finiteness of a laboratory surface; c) the optimal use of the Minkowski quantum vacuum, through the choice of this Minkowski-static boundary.

hep-th↗

Hadron Freeze-Out and Unruh Radiation

We consider hadron production in high energy collisions as an Unruh radiation phenomenon. This mechanism describes the production pattern of newly formed hadrons and is directly applicable at vanishing baryochemical potential, mu = 0. It had already been found to correctly yield the hadronisation temperature, T_h = sqrt(sigma / 2 pi) = 165 MeV in terms of the string tension sigma. Here we show that the Unruh mechanism also predicts hadronic freeze-out conditions, giving s/T_h^3 = 3 pi^2 / 4 = 7.4 in terms of the entropy density s and E/N = \sqrt(2 pi sigma) = 1.09 for the average energy per hadron. These predictions provide a theoretical basis for previous phenomenological results and are also in accord with recent lattice studies.

hep-ph↗

Graphene: QFT in curved spacetimes close to experiments

A recently proposed step-by-step procedure, to merge the low-energy physics of the $π$-bonds electrons of graphene, and quantum field theory on curved spacetimes, is recalled. The last step there is the proposal of an experiment to test a Hawking-Unruh effect, emerging from the model, that manifests itself as an exact (within the model) prediction for the electronic local density of states, in the ideal case of the graphene membrane shaped as a Beltrami pseudosphere. A discussion about one particular attempt to experimentally test the model on molecular graphene is presented, and it is taken as an excuse to solve some basic issues that will help future experiments. In particular, it is stated that the effect should be visible on generic surfaces of constant negative Gaussian curvature, that are infinite in number.

gr-qc↗

The Hawking-Unruh phenomenon on graphene

We find that, for a very specific shape of a monolayer graphene sample, a general relativistic-like description of a back-ground spacetime for graphene's conductivity electrons is very natural. The corresponding electronic local density of states is of finite temperature. This is a Hawking-Unruh effect that we propose to detect through an experiment with a Scanning Tunneling Microscope.

cond-mat.mtrl-sci↗

Using Weyl symmetry to make Graphene a real lab for fundamental physics

In the first attempt to introduce gauge theories in physics, Hermann Weyl, around the 1920s, proposed certain scale transformations to be a fundamental symmetry of nature. Despite the intense use of Weyl symmetry that has been made over the decades, in various theoretical settings, this idea never found its way to the laboratory. Recently, building-up from work by Lochlainn O'Raifeartaigh and collaborators on the Weyl-gauge symmetry, applications of Weyl-symmetry to the electronic properties of graphene have been put forward, first, in a theoretical setting, and later, in an experimental proposal. Here I review those results, by enlarging and deepening the discussion of certain aspects, and by pointing to the steps necessary to make graphene a testing ground of fundamental ideas.

hep-th↗

Alternative Symmetries in Quantum Field Theory and Gravity

A general, incomplete and partisan overview of various areas of the theoretical investigation is presented. Most of this activity stems from the search for physics beyond quantum field theory and general relativity, a titanic struggle that, in my opinion, empowered the symmetry principles to a dangerous level of speculation. In the works (that are my own) commented upon here the attempt has been to proceed by holding to certain epistemological pillars (usually absent from the too speculative theories) such as, e.g., four or less dimensions, proposals for experimental tests of radical ideas, wide cross-fertilization, etc.. As for the latter, the enterprise is undertaken within a theoretical perspective that pushes till condensed matter and even biology the cross-fertilization between ``branches of physics''.

hep-th↗

Comment on "Noncommutative gauge theories and Lorentz symmetry, Phys. Rev. D {\bf 70}, 125004 (2004) by R.Banerjee, B.Chakraborty and K.Kumar"

We show that Lorentz symmetry is generally absent for noncommutative (abelian) gauge theories and obtain a compact formula for the divergence of the Noether currents that allows a throughout study of this instance of symmetry violation. We use that formula to explain why the results of "Noncommutative gauge theories and Lorentz symmetry", Phys. Rev. D {\bf 70}, 125004 (2004) by R.Banerjee, B.Chakraborty and K.Kumar, interpreted there as new criteria for Lorentz {\it invariance}, are in fact just a particular case of the general expression for Lorentz {\it violation} obtained here. Finally, it is suggested that the divergence-formula should hold in a vast class of cases, such as, for instance, the Standard Model Extension.

hep-th↗

Weyl-Gauge Symmetry of Graphene

The conformal invariance of the low energy limit theory governing the electronic properties of graphene is explored. In particular, it is noted that the massless Dirac theory in point enjoys local Weyl symmetry, a very large symmetry. Exploiting this symmetry in the two spatial dimensions and in the associated three dimensional spacetime, we find the geometric constraints that correspond to specific shapes of the graphene sheet for which the electronic density of states is the same as that for planar graphene, provided the measurements are made in accordance to the inner reference frame of the electronic system. These results rely on the (surprising) general relativistic-like behavior of the graphene system arising from the combination of its well known special relativistic-like behavior with the less explored Weyl symmetry. Mathematical structures, such as the Virasoro algebra and the Liouville equation, naturally arise in this three-dimensional context and can be related to specific profiles of the graphene sheet. Speculations on possible applications of three-dimensional gravity are also proposed.

hep-th↗

Mixing-induced Spontaneous Supersymmetry Breaking

It is conjectured that flavor mixing furnishes a universal mechanism for the spontaneous breaking of supersymmetry. The conjecture is proved explicitly for the mixing of two Wess--Zumino $\mathcal{N}=1$ supermultiplets and arguments for its general validity are given. The mechanism relies on the fact that, despite mixing treats fermions and bosons symmetrically, both the fermionic and the bosonic zero point energies are shifted by a positive amount and this kind of shift does not respect supersymmetry.

hep-th↗

On (Schröedinger's) quest for new physics for life

Two recent investigations are reviewed: quantum effects for DNA aggregates and scars formation on virus capsids. The possibility that scars could explain certain data recently obtained by Sundquist's group in electron cryotomography of immature HIV-1 virions is also briefly addressed. Furthermore, a bottom-up reflection is presented on the need to invent new physics to pave the way to a rigorous physical theory of biological phenomena. Our experience in the two researches presented here and our personal interpretation of Schroedinger's vision are behind the latter request.

q-bio.OT↗

Effects of Quantum Vacuum Fluctuations of the Electric Field on DNA Condensation

By assuming that not only counter-ions but DNA molecules as well are thermally distributed according to a Boltzmann law, we propose a modified Poisson-Boltzmann equation at the classical level as starting point to compute the effects of quantum fluctuations of the electric field on the interaction among DNA-cation complexes. The latter are modeled here as infinite one-dimensional wires ($δ$-functions). Our goal is to single out such quantum-vacuum-driven interaction from the counterion-induced and water-related interactions. We obtain a universal, frustration-free Casimir-like (codimension 2) interaction that extensive numerical analysis show to be a good candidate to explain the formation and stability of DNA aggregates. Such Casimir energy is computed for a variety of configurations of up to 19 DNA strands in a hexagonal array. It is found to be strongly many-body.

q-bio.QM↗

Scar-Driven Shape-Changes of Virus Capsids

We propose that certain patterns (scars) -- theoretically and numerically predicted to be formed by electrons arranged on a sphere to minimize the repulsive Coulomb potential (the Thomson problem) and experimentally found in spherical crystals formed by self-assembled polystyrene beads (an instance of the {\it generalized} Thomson problem) -- could be relevant to extend the classic Caspar and Klug construction for icosahedrally-shaped virus capsids. The main idea is that scars could be produced on the capsid at an intermediate stage of its evolution and the release of the bending energy present in scars into stretching energy could allow for shape-changes. The conjecture can be tested in experiments and/or in numerical simulations.

q-bio.QM↗

Do quantum effects hold together DNA condensates?

The classical electrostatic interaction between DNA molecules in water in the presence of counterions is reconsidered and we propose it is governed by a modified Poisson-Boltzmann equation. Quantum fluctuations are then studied and shown to lead to a vacuum interaction that is numerically computed for several configurations of many DNA strands and found to be strongly many-body. This Casimir vacuum interaction can be the ``glue'' holding together DNA molecules into aggregates.

q-bio.QM↗

Virus Structure: From Crick and Watson to a New Conjecture

We conjecture that certain patterns (scars), theoretically and numerically predicted to be formed by electrons arranged on a sphere to minimize the repulsive Coulomb potential (the Thomson problem) and experimentally found in spherical crystals formed by self-assembled polystyrene beads (an instance of the generalized Thomson problem), could be relevant to extend the classic Caspar and Klug construction for icosahedrally-shaped virus capsids. The main idea is that scars could be produced at an intermediate stage of the assembly of the virus capsids and the release of the bending energy present in scars into stretching energy could allow for a variety of non-spherical capsids' shapes. The conjecture can be tested in experiments on the assembly of artificial protein-cages where these scars should appear.

q-bio.QM↗

Three Questions on Lorentz Violation

We review the basics of the two most widely used approaches to Lorentz violation - the Stardard Model Extension and Noncommutative Field Theory - and discuss in some detail the example of the modified spectrum of the synchrotron radiation. Motivated by touching upon such a fundamental issue as Lorentz symmetry, we ask three questions: What is behind the search for Lorentz violation? Is String Theory a physical theory? Is there an alternative to Supersymmetry?

physics.pop-ph↗