arXiv subjects

Nguyen Ai Viet

Publications and source records attributed to Nguyen Ai Viet.

17 recordsLinked to original sources

arXiv2024

Checking the $^8$Be anomaly with a two-arm electron positron pair spectrometer

We have repeated the experiment performed recently by Krasznahorkay et al., (Phys. Rev. Lett. 116, 042501 (2016)), which may indicate a new particle called X17 in the literature. In order to get a reliable, and independent result, we used a different type of electron-positron pair spectrometer which have a more simple acceptance/efficiency as a function of the correlation angle, but the other conditions of the experiment were very similar to the published ones. We could confirm the presence of the anomaly measured at the E$_x$=18.15 MeV resonance, and also confirm their absence at the E$_x$=17.6 MeV resonance, and at E$_p$= 800 keV off resonance energies.

nucl-ex↗

arXiv2021

The Standard Model and Dark Matter in a unified Einstein-Dirac system with discrete extra dimensions

The Dirac-Einstein system of quark-leptons coupled to gravity is constructed generalized in the space-time extended with chiral and dark discrete extra dimensions. The Einstein's gravity, all the Standard Model's gauge vector, and Higgs fields together with a dark photon, whose mass is generated by a dark Higgs scalar, can be incorporated in this framework as components of the generalized vielbein. The Standard Model derived from the extended Einstein-Hilbert action must satisfy some conditions leading to the predictions of Weinberg angle, Higgs and top quark masses in excellent agreement with experiments. Since, the Dirac operator extended by discrete derivatives has resulted in a non-diagonal mass matrix, which mixes each quark-lepton with its Kaluza-Klein partner. On one hand, the small mixing angle set a Stueckelberg mass to the quark-leptons' Kaluza-Klein partners at least in the hundreds TeV range. On the other hand, it implies weak couplings between the Kaluza-Klein partners of quark-leptons and the Standard Model's gauge vector fields. This feature indicates that these Kaluza-Klein modes can be considered as candidates of dark matters.

hep-ph↗

arXiv2021

Massive photon and fermion mixing as manifestations of an extra discrete dimension in bilayer systems

Discrete dimension is introduced via an extended Dirac operator to include the interlayer interactions in a geometric framework of generic $d+1$-dimensional bilayer systems. The photon and its Kaluza-Klein partners in this extended space-time will involve a pair of vector fields together with a scalar field, which describes a pair of local jumping between the layers. The quartic potential of the scalar field triggers an abelian Higgs mechanism, which gives a mass to one vector field, which describes a short-range interaction. The discrete derivative along the extra dimension generates a non-diagonal mass matrix, whose eigenstates mix the fermions on two layers with a mixing angle. The couplings of the Kaluza-Klein siblings of photon including massless, massive, and scalar ones with the mass eigenstates of fermions will also depend on the mixing angle. Thus interlayer interactions in bilayer systems are manifested elegantly by these new features via the extra discrete dimension. In specific cases, the short-range force, weak and strong coupling regimes of the fermions with different masses can lead to new physical consequences to be discovered in different realistic $2+1$ and $3+1$-dimensional bilayer systems.

hep-th↗

arXiv2019

Extra dimension of space-time exposed by anomalies at low energy

Recent experimental observations are shown to be quantitatively consistent with an extended concept of space-time having a discrete extra dimension of two points at the distance of 11.8 fm together with a nontrivial metric structure. In such a space-time, fermions appear in pair with their Kaluza-Klein siblings. The usual electromagnetic field is accompanied with a new vector boson $X17$, which receives a mass of $17~MeV$ from another Kaluza-Klein partner, a scalar boson $H$ of a mass in the range of $0.5-793~keV$ via an abelian Higgs mechanism. At a low energy scale, where nucleons can be treated as structureless in a good approximation, the natural particle model involving nucleons, electron, neutrino and their Kaluza-Klein partners coupled to the electromagnetic field and the massive vector boson $X7$ can lead to new phenomenological consequences, which are verifiable at the currently accessible energy.

hep-ph↗

arXiv2018

Structural phase transition and band gap of uniaxially deformed (6,0) carbon nanotube

The atomic and band structures of the (6,0) zigzag carbon nanotube at its axial elongation are calculated by semiempirical molecular orbital and by tight-binding methods. The ground state of the nanotube is found to have a Kekule structure with four types of bonds and difference between lengths of long and short bonds of about 0.005 nm. The structural phase transition is revealed at ~9% elongation, resulting in a quinoid structure with two types of bonds. This structural phase transition is followed by the transition from a narrow gap to moderate gap semiconductor. Validity of the semiempirical PM3 method is discussed.

cond-mat.mes-hall↗

arXiv2003

Some Remarks on Gravity in Noncommutative Spacetime and a New Solution to the Structure Equations

In this paper, starting from the common foundation of Connes' noncommutative geometry (NCG) [1,2,3,4], various possible alternatives in the formulation of a theory of gravity in noncommutative spacetime are discussed in detail. The diversity in the final physical content of the theory is shown to the the consequence of the arbitrariness in each construction steps. As an alternative in the last step, when the staructure equations are to be solved, a minimal set of constraints on the torsion and connection is found to determine all the geometric notions in terms of metric. In the Connes-Lott model of noncommutative spacetime, in order to keep the full spectrum of the discretized Kaluza-Klein theory [5], it is necessary to include the torsion in the generalized Einstein-Hilbert-Cartan action.

hep-th↗

arXiv2003

Chiral spinors and gauge fields in noncommutative curved space-time

The fundamental concepts of Riemannian geometry, such as differential forms, vielbein, metric, connection, torsion and curvature, are generalized in the context of non-commutative geometry. This allows us to construct the Einstein-Hilbert-Cartan terms, in addition to the bosonic and fermionic ones in the Lagrangian of an action functional on non-commutative spaces. As an example, and also as a prelude to the Standard Model that includes gravitational interactions, we present a model of chiral spinor fields on a curved two-sheeted space-time with two distinct abelian gauge fields. In this model, the full spectrum of the generalized metric consists of pairs of tensor, vector and scalar fields. They are coupled to the chiral fermions and the gauge fields leading to possible parity violation effects triggered by gravity.

hep-th↗

arXiv2000

Matter Fields in Curved Space-Time

We study the geometry of a two-sheeted space-time within the framework of non-commutative geometry. As a prelude to the Standard Model in curved space-time, we present a model of a left- and a right- chiral field living on the two sheeted-space time and construct the action functionals that describe their interactions.

hep-th↗

arXiv1995

A Discretized Version of Kaluza-Klein Theory with Torsion and Massive Fields

We consider an internal space of two discrete points in the fifth dimension of the Kaluza-Klein theory by using the formalism of noncommutative geometry developed in a previous paper \cite{VIWA} of a spacetime supplemented by two discrete points. With the nonvanishing internal torsion 2-form there are no constraints implied on the vielbeins. The theory contains a pair of tensor, a pair of vector and a pair of scalar fields. Using the generalized Cartan structure equation we are able not only to determine uniquely the hermitian and metric compatible connection 1-forms, but also the nonvanishing internal torsion 2-form in terms of vielbeins. The resulting action has a rich and complex structure, a particular feature being the existence of massive modes. Thus the nonvanishing internal torsion generates a Kaluza-Klein type model with zero and massive modes.

hep-th↗

arXiv1995

Chern-Simons terms in Noncommutative Geometry and its application to Bilayer Quantum Hall Systems

Considering bilayer systems as extensions of the planar ones by an internal space of two discrete points, we use the ideas of Noncommutative Geometry to construct the gauge theories for these systems. After integrating over the discrete space we find an effective $2+1$ action involving an extra complex scalar field, which can be interpreted as arising from the tunneling between the layers. The gauge fields are found in different phases corresponding to the different correlations due to the Coulomb interaction between the layers. In a particular phase, when the radial part of the complex scalar field is a constant, we recover the Wen-Zee model of Bilayer Quantum Hall systems. There are some circumstances, where this radial part may become dynamical and cause dissipation in the oscillating supercurrent between the layers.

hep-th↗

arXiv1995

Puzzle in the Charmed $D_s$ meson decays into pions: Could the light quarks be not so light?

The inclusive decay rate into pions of the charmed $D_s$ meson is surprisingly larger than estimates expected from the $W$ annihilation, adopting commonly used values of current-algebra up and down quark masses. We then go beyond this tree diagram and consider possible QCD effects that might cause such a large rate. There are two; the first one is related to the spectator decay $ c{\bar s} \rightarrow s{\bar s} + u {\bar d}$ followed by $ s {\bar s} \rightarrow d{\bar d}~,~ u{\bar u}$ via two-gluon exchange box diagram. The second one is a gluon emission in weak annihilation for which the usual helicity suppression is vitiated: $D_s\rightarrow W+g$ followed by $ W\rightarrow u {\bar d},~ g\rightarrow d{\bar d},~u{\bar u}$. These two contributions, however, turn out to be insufficient to explain data, implying that the puzzle could be understood if the up, down quarks have higher mass values. Furthermore, on the basis of experimental informations on the spectral function $ρ_{3π}(Q^2)$ deduced from the exclusive $ D_s \rightarrow 3π$ mode, the QCD sum rules also point to a higher mass for light quarks.

hep-ph↗

arXiv1994

Noncommutative Geometry and a Discretized Version of Kaluza-Klein Theory with a Finite Field Content

We consider a four-dimensional space-time supplemented by two discrete points assigned to a $Z_2$ algebraic structure and develop the formalism of noncommutative geometry. By setting up a generalised vielbein, we study the metric structure. Metric compatible torsion free connection defines a unique finite field content in the model and leads to a discretized version of Kaluza-Klein theory. We study some special cases of this model that illustrate the rich and complex structure with massive modes and the possible presence of a cosmological constant.

hep-th↗

arXiv1994

Predictions of noncommutative space-time

An unified structure of noncommutative space-time for both gravity and particle physics is presented. This gives possibilities of testing the idea of noncommutative space-time at the currently available energy scale. There are several arguments indicating that noncommutative space-time is visible already at the electroweak scale. This noncommutative space-time predicts the top quark mass m_t \sim 172 GeV, the Higgs mass M_H \sim 241 GeV and the existence of a vector meson and a scalar, which interact universally with the matter.

hep-ph↗

arXiv1994

Gravity and Electromagnetism in Noncommutative Geometry

We present a unified description of gravity and electromagnetism in the framework of a $Z_2$ noncommutative differential calculus. It can be considered as a ``discrete version" of Kaluza-Klein theory, where the fifth continuous dimension is replaced by two discrete points. We derive an action which coincides with the dimensionally reduced one of the ordinary Kaluza-Klein theory.

hep-th↗

arXiv1993

Heavy diquark in baryons containing a single heavy quark and the weak form factors

It is shown that the number of independent weak form factors collapses if the heavy diquark exists inside the baryons containing a single heavy quark. The relations between the weak form factors are quite different in the case of light diquark. So a careful analysis on the future data of the weak form factors would clarify that in those baryons the correlation between the heavy quark and a light quark is stronger or weaker than the one between two light quarks.

hep-ph↗

arXiv1993

Heavy diquark effective theory and supersymmetry of hadrons containing a single heavy quark

A new supersymmetry is proposed for hadrons containing a single heavy quark. This supersymmetry is based on a new approximation to those hadrons, which we would consider as a further step beyond the spectator light diquark model of baryons. The heavy diquark effective theory is constructed by the techniques introduced in a different context by Georgi and Wise$^1$ and by Carone$^2$. This theory can be incorporated into a supersymmetric theory together with Heavy Quark Effective Theory, and leads to a common universal Isgur-Wise function for mesons and baryons./.

hep-ph↗

arXiv1993

Magnetic Monopoles in the Einstein-Yang-Mills-Higgs System

We study the Yang-Mills-Higgs system within the framework of general relativity. In the static situation, using Bogomol'nyi type analysis, we derive a positive-definite energy functional which has a lower bound. Specializing to the gauge group $SU(2)$ and the t'Hooft-Polyakov ansatz for the gauge and Higgs fields, we seek static, spherically symmetric solutions to the coupled system of equations in both the isotropic and standard coordinate systems. In both cases, in the spontaneously broken symmetry situation, we find great simplications reducing the solutions of the coupled system to the solution of a single non-linear differential equation, different one in each case, but well-known in other contexts of physics. We find abelian and non-abelian monopole solutions with gravitational fields playing the role of Higgs fields in providing attraction that balances the repulsion due to the gauge fields. Numerical solutions indicate the possibility of blackhole horizons inside the monopoles enclosing the singularity at the origin. Such non-abelian monopoles are then the analogs of Reissner-Nordström blackholes with magnetic charge.

hep-ph↗