arXiv subjects

Anca Tureanu

Publications and source records attributed to Anca Tureanu.

At least 19 recordsLinked to original sources

arXiv2026

Renormalizable and unitary nonlocal quantum field theory with CPT violation and its implication

It is a common belief that any relativistic nonlocal quantum field theory encounters either the problem of renormalizability or unitarity or both of them. It is also known that any local relativistic quantum field theory (QFT) possesses the CPT symmetry. In this Letter we show that a previously proposed nonlocal Lorentz invariant QFT, which violates the CPT theorem, is both renormalizable and unitary, thus being a first presented example in the literature of such a nonlocal theory. The theory satisfies the requirement of causality as well. A further generalization of such a nonlocal QFT to include the gauge theories is also envisaged. In particular, dressing such a Standard Model with a CP violating phase, will make the theory satisfying most of the necessary criteria to finally explain the baryon asymmetry of the universe by a viable QFT. As for the necessity of baryon number violation, there are hopefully several possibilities such as by GUT and electroweak baryogenesis, leptogenesis or sphalerons.

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arXiv2025

On Massive Neutrinos and Coherence in Neutrino Oscillations

We examine the central tenet of the current standard theory of neutrino oscillations, namely the assumption that neutrinos are emitted and detected as flavour neutrino states, which are coherent superpositions of massive neutrino states of different masses. We prove that all the quantum mechanical and quantum field theoretical arguments, including the invocation of the uncertainty principle and the wave packet description of massive neutrinos, entail the production of neutrinos as statistical ensembles of massive neutrino states. As the states in a statistical ensemble do not interfere, neutrino oscillations cannot be explained by the superposition of massive states. We point out that neutrino oscillations in vacuum can be consistently formulated in theories which include, among other assumptions, the premise that the asymptotic states are massless flavour neutrinos.

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arXiv2025

Below the Schwinger critical magnetic field value, quantum vacuum and gamma-ray bursts delay

A magnetic field above the Schwinger critical value $B_{\rm crit} = 10^9$ Tesla is much higher than any magnetic field known by now in the interstellar bulk except in the vicinity of observed magnetars with magnetic fields between $10^9$ and $10^{11}~$Tesla. Above the critical magnetic field, calculated by Schwinger in the lowest order perturbation in quantum electrodynamics (QED), one reaches the threshold for electron-positron pair creation, which has interesting consequences. Therefore, finding out whether one could encounter some consequences of interest also for the values of the magnetic field below the Schwinger critical point, we invoke the next higher-order effect in QED, which is emerging from the Quantum Vacuum Effect. The latter is equivalent to the use of the Euler-Heisenberg effective theory in nonlinear electrodynamics, where the Lagrangian has a term with a higher power, $B^4$. In this case, in the region $B<B_{\rm crit}$, we show that interesting effects appear, among them the Cherenkov radiation and the reduction in the speed of light. The latter effects appear because of the quantum vacuum mimicking a medium. We also present quantitative arguments for such a close analogy. As a rough estimate, we show that the time delay $\tau$ of gamma-ray bursts (GRB) having traveled through the entire cosmological distances in an average strong magnetic field such as $10^6~$Tesla, reaches an experimentally considerable value of $\tau = 2.4$ hours. In the vicinity of magnetars, the magnetic field is much stronger, of the order of $10^9-10^{11}$ Tesla. However, in this case the linear scale of GRB trajectory through such regions would be much smaller. For the latter, we give an estimate for the number of the magnetars along the trajectory and also for the delay. Finally, we shall dwell on the recently raised issue in the literature, namely the Lorentz invariance violation (LIV).

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arXiv2024

Note on a BCS analogy of Majorana neutrinos

In this note, we discuss an analogy between the BCS theory and the seesaw model of neutrinos. We believe that the analogy indicates some fundamental aspects of Majorana neutrinos. A paper on the issue has been recently presented, and we would like to describe the background of the paper together with our personal views on the problem. In essence, the conventional construction of a Majorana neutrino from a chiral fermion is too simplified, and we argue that one would actually have to go through a Bogoliubov-type canonical transformation to generate two Majorana fermions from an effective single Dirac fermion in the seesaw model.

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arXiv2024

Neutrino Flavour Waves Through the Quantum Vacuum: A Theory of Oscillations

We propose a theory for neutrino oscillations, in which the flavour neutrinos are treated as waves of massless particles propagating in a "refractive quantum vacuum" and obeying a relativistically covariant equation of motion. The difference in strength between weak interactions and mass-generating interactions is argued to allow for the production and detection of flavour neutrinos in weak interactions as massless particles. They experience the mass-generating interactions as coherent forward scattering in the Brout-Englert-Higgs vacuum, which induces macroscopically multi-refringent effects. The flavour neutrino wave is then found to have a universal effective refractive mass in vacuum and a unique group velocity for a given energy. The coherence of the wave is manifest throughout and, at every moment of the propagation, the energy of the waves is the same. The standard oscillation probability in vacuum is obtained and the effects of matter are incorporated in a natural way.

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arXiv2024

Two classes of Majorana neutrinos in the seesaw model

The commonly used pseudo-C symmetry $(\nu_{L})^{c}=C\overline{\nu_{L}}^{T}$ is not defined in Lagrangian field theory. In general, there exist two classes of Majorana fermions; the first is associated with the Dirac-type fermion with the conventional C and P symmetries, and the second is associated with the Weyl-type fermion defined by CP symmetry only and formally characterised by the pseudo-C symmetry. Taking the seesaw model as an example, it is shown that a generalized Pauli--G\"{u}rsey (or Bogoliubov-type) canonical transformation converts the neutrino defined by the Weyl-type fermion to the neutrino defined by the Dirac-type fermion and thus to the conventional Majorana fermion, while preserving the canonical anti-commutation relations. The mixing angles in the weak lepton sector are not modified by this generalized Pauli--G\"{u}rsey transformation.

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arXiv2024

Galaxy groups in the presence of Cosmological Constant: Increasing the Masses of Groups

The boundaries of galaxy groups and clusters are defined by the interplay between the Newtonian attractive force and the decoupling from the local expansion of the Universe. This work extends the definition of a zero radial acceleration surface (ZRAS) and the turnaround surface (TS) for a general distribution of the masses in an expanding background, governed by the cosmological constant. We apply these definitions to different galaxy groups in the local Universe, mapping these groups up to ten megaparsec distances. We discuss the dipole and the quadrupole rate for the Local Group of Galaxies and the implementations on the Hubble diagram correction and galaxy groups virialization. With these definitions, we present the surfaces showing the interplay between the local expansion vs the local Newtonian attraction for galaxy groups in the local Universe. Further, we estimate the masses of different galaxy groups and show that the inclusion of the Cosmological Constant in the analysis predicts these masses to be higher by 5-10\%. For instance the Local Group of Galaxies is estimated to be $(2.47 \pm 0.08) \cdot 10^{12} M_{\odot}$. For the groups with enough tracers close to the TS, the contribution of the Cosmological Constant makes the masses to be even higher. The results show the importance of including the local cosmic expansion in analyzing the Cosmic Flow of the local Universe.

astro-ph.GA↗

arXiv2023

Reciprocal of the CPT theorem

The CPT theorem originally proven by L\"uders and Pauli ensures the equality of masses, lifetimes, magnetic moments and cross sections of any particle and its antiparticle. We show that in a Lorentz invariant quantum field theory described by its Lagrangian, CPT-violating interaction alone does not split the masses of an elementary particle and its antiparticle but breaks only the equality of lifetimes, magnetic moments and cross sections. However, CPT violation in the mass term of a field in the Lagrangian, which can be attributed to be due to the size of the particle described by a form factor, breaks only the equality of masses. Also it is shown that the two separate effects of CPT violation in the interaction terms or in the mass term do not mix due to higher quantum corrections and remain distinguishable. Thus, we urge the experimentalists to search for such observable effects concerning differences in the masses, magnetic moments, lifetimes and cross sections between the elementary or bound state particles and their antiparticles. In the case of CPT violation only in the mass term, besides the difference in the masses of elementary bound state particles and their antiparticles, there will be also an extremely tiny difference in the lifetimes of bound states due to the difference in their phase spaces. From the details of calculations, it appears that the separate effects of the CPT violation described above are quite general, neither depending on how the nonlocality is achieved, nor depending on what this violation is due to: due to T violation, as considered in the present work, which can be attributed to a cosmological direction of time; to CP or to both T and CP violations. The latter two cases satisfy the Sakharov's conditions for explaining the baryon asymmetry in the Universe.

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arXiv2023

Neutrino Oscillations by a Manifestly Coherent Mechanism and Massless vs. Massive Neutrinos

The neutrino oscillations in vacuum are derived in a manifestly coherent scheme. The mechanism is operative in a quantum field theoretical framework, justifying nevertheless a formal analogy with quantum mechanical two- (or more) level systems and their oscillatory behaviour. Both the flavour states and the massive states are eigenstates of certain Hamiltonians which, in special conditions, can be argued to share the same Hilbert space. In this scheme, flavour neutrinos are massless and play the role of asymptotic states for any interactions, including the weak interactions, while massive neutrinos are effective propagation states. The vacuum is interpreted as a medium, where the flavour neutrinos undergo coherent forward scatterings which modify their energy and mix their flavour. The treatment of matter conversion and MSW effect fits in naturally; the extension to other neutral particle oscillations, like $K_0-\bar K_0$, is straightforward. The scheme is eclectic insofar as it combines seamlessly quantum field theory and quantum mechanics.

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arXiv2021

Seesaw, coherence and neutrino oscillations

We present a prescription for consistently constructing non-Fock coherent flavour neutrino states within the framework of the seesaw mechanism, and establish that the physical vacuum of massive neutrinos is a condensate of Standard Model massless neutrino states. The coherent states, involving a finite number of massive states, are derived by constructing their creation operator. Such a construction is the key requirement so that the oscillations of particles indeed occur. We comment on the inherent non-unitarity of the oscillation probability induced by the requirement of coherence.

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arXiv2020

Intrinsic quantum coherence in particle oscillations

The quantum field theoretical description of coherence in the oscillations of particles, especially neutrinos, is a standing problem in particle physics. In this talk, several inconsistencies of the standard approach to particle oscillations will be explained, and how they are resolved in a process-independent manner, by a novel approach inspired by the Bardeen--Cooper--Schrieffer theory of superconductivity and the Nambu--Jona-Lasinio model. The formalism leads to corrections to the neutrino oscillation probability originally written by Pontecorvo and Gribov, however the standard probability is validated in the ultrarelativistic neutrino limit. The massive neutrino states are interpreted as quasiparticles on a vacuum condensate of "Cooper pairs" of massless flavour neutrinos. The newly defined oscillating particle states are for neutrino oscillations what the Klauder--Sudarshan--Glauber coherent states are for quantum optics.

hep-ph↗

arXiv2020

Parity of the neutron consistent with neutron-antineutron oscillations

In the analysis of neutron-antineutron oscillations, it has been recently argued in the literature that the use of the $i\gamma^{0}$ parity $n^{p}(t,-\vec{x})=i\gamma^{0}n(t,-\vec{x})$ which is consistent with the Majorana condition is mandatory and that the ordinary parity transformation of the neutron field $n^{p}(t,-\vec{x}) = \gamma^{0}n(t,-\vec{x})$ has a difficulty. We show that a careful treatment of the ordinary parity transformation of the neutron works in the analysis of neutron-antineutron oscillations. Technically, the CP symmetry in the mass diagonalization procedure is important and the two parity transformations, $i\gamma^{0}$ parity and $\gamma^{0}$ parity, are compensated for by the Pauli-G\"ursey transformation. Our analysis shows that either choice of the parity gives the correct results of neutron-antineutron oscillations if carefully treated.

hep-ph↗

arXiv2020

Comment on the Comment on the paper "Can oscillating neutrino states be formulated universally?''

Recently, our work regarding the definition of oscillating neutrino states in Eur. Phys. J. C 80: 68 (2020), arxiv:1902.01232 [hep-ph] has been commented upon in arXiv:2004.04739 [hep-ph]. In this note we show that, contrary to the claim in the comment, our above-mentioned work cannot be reproduced in the scheme of the so-called flavour Fock space approach described in the comment. Moreover, we prove explicitly that a flavour Fock space cannot exist in a model with massive mixed neutrinos. If the flavour Fock space scheme were viable, it would necessarily lead, as a consequence of Coleman's theorem, to the flavour number invariance of the Hamiltonian of mixed neutrino fields, while the Hamiltonian is by construction flavour number violating. Quod est absurdum.

hep-ph↗

arXiv2019

Can Oscillating Neutrino States Be Formulated Universally?

A standing problem in neutrino physics is the consistent and universal definition of oscillating neutrino states as coherent superpositions of massive neutrino states. This problem is solved in a quantum field theoretical framework of neutrino mixing developed in analogy with the Nambu--Jona-Lasinio model for the dynamical generation of nucleon masses. The massive neutrino states are Bogoliubov quasiparticles and their vacuum is a condensate of "Cooper pairs" of massless flavour neutrinos. Their superpositions as oscillating neutrino states have intrinsic quantum coherence by construction. In this quantization framework, the standard phenomenological flavour neutrino states and oscillation probability formula are validated in the ultrarelativistic approximation.

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arXiv2018

Seesaw mechanism and pseudo C-symmetry

It is shown that the specific "charge conjugation" transformation used to define the Majorana fermions in the conventional seesaw mechanism, namely $(\nu_{R})^{C}=C\bar{\nu_{R}}^{T}$ for a chiral fermion $\nu_{R}$ (and similarly for $\nu_{L}$), is a hidden symmetry associated with CP symmetry, and thus it formally holds independently of the P- and C-violating terms in the CP invariant Lagrangian and it is in principle applicable to charged leptons and quarks as well. This hidden symmetry, however, is not supported by a consistent unitary operator and thus it leads to mathematical (operatorial) ambiguities. When carefully examined, it also fails as a classical transformation law in a Lorentz invariant field theory. To distinguish it from the standard charge conjugation symmetry, we suggest for it the name of pseudo C-symmetry. The pseudo C-symmetry is effective to identify Majorana neutrinos analogously to the classical Majorana condition. The analysis of CP breaking in weak interactions is performed using the conventional CP transformation, which is defined independently of the pseudo C-transformation, in the seesaw model after mass diagonalization. A way to ensure an operatorially consistent formulation of C-conjugation is to formulate the seesaw scheme by invoking a relativistic analogue of the Bogoliubov transformation.

hep-ph↗

arXiv2018

Sakharov's induced gravity and the Poincar\'e gauge theory

We explore Sakharov's seminal idea that gravitational dynamics is induced by the quantum corrections from the matter sector. This was the starting point of the view that gravity has an emergent origin, which soon gained impetus due to the advent of black hole thermodynamics. In the generalized framework of Riemann--Cartan spacetime with both curvature and torsion, the induced gravitational action is obtained for free nonminimally coupled scalar and Dirac fields. For a realistic matter content, the induced Newton constant is obtained to be of the magnitude of the ultraviolet cutoff, which implies that the cutoff is of the order of the Planck mass. Finally, we conjecture that the action for any gauge theory of gravity at low energies can be induced by Sakharov's mechanism. This is explicitly shown by obtaining the Poincar\'e gauge theory of gravity.

hep-th↗

arXiv2018

Quantum Field Theory of Particle Oscillations: Neutron-Antineutron Conversion

We formulate the quantum field theory description of neutron-antineutron oscillations in the framework of canonical quantization, in analogy with the Bardeen--Cooper--Schrieffer (BCS) theory and the Nambu--Jona-Lasinio model. The physical vacuum of the theory is a condensate of pairs of {\it would-be neutrons and antineutrons} in the absence of the baryon-number violating interaction. The quantization procedure defines uniquely the mixing of massive Bogoliubov quasiparticle states which represent the neutron. In spite of not being mass eigenstates, neutron and antineutron states are defined on the physical vacuum and the oscillation formulated in asymptotic states. The exchange of baryonic number with the vacuum condensate engenders what may be observed as neutron-antineutron oscillation. The convergence between the present canonical approach and the Lagrangian/path integral approach to neutron oscillations is shown by the calculation of the anomalous (baryon-number violating) propagators. The quantization procedure proposed here can be extended to neutrino oscillations and, in general, to any particle oscillations.

hep-ph↗

arXiv2017

Baryon number violation and novel canonical anti-commutation relations

The possible neutron-antineutron oscillation is described by an effective quadratic Lagrangian analogous to the BCS theory. It is shown that the conventional equal-time anti-commutation relations of the neutron variable $n(t,\vec{x})$ are modified by the baryon number violating terms. This is established by the Bjorken--Johnson--Low prescription and also by the canonical quantization combined with equations of motion. This novel canonical behavior can give rise to an important physical effect, which is illustrated by analyzing the Lagrangian that violates the baryon number but gives rise to the degenerate effective Majorana fermions and thus no neutron-antineutron oscillation. Technically, this model is neatly treated using a relativistic analogue of the Bogoliubov transformation.

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