Instanton induced charged fermion and neutrino masses in a minimal Standard Model scenario from intersecting D-branes

String instanton Yukawa corrections from Euclidean D-branes are investigated in an effective Standard Model theory obtained from the minimal U(3)xU(2)xU(1) D-brane configuration. In the case of the minimal chiral and Higgs spectrum, it is found that superpotential contributions are induced by string instantons for the perturbatively forbidden entries of the up and down quark mass matrices. Analogous non-perturbative effects generate heavy Majorana neutrino masses and a Dirac neutrino texture with factorizable Yukawa couplings. For this latter case, a specific example is worked out where it is shown how this texture can reconcile the neutrino data.Comment: 17 pages, 3 figure

Superheavy Dark Matter with Discrete Gauge Symmetries

We show that there are discrete gauge symmetries protect naturally heavy X particles from decaying into the ordinary light particles in the supersymmetric standard model. This makes the proposal very attractive that the superheavy X particles constitute a part of the dark matter in the present universe. It is more interesting that there are a class of discrete gauge symmetries which naturally accommodate a long-lived unstable X particle. We find that in some discrete Z_{10} models, for example, a superheavy X particle has lifetime \tau_X \simeq 10^{11}-10^{26} years for its mass M_X \simeq 10^{13}-10^{14} GeV. This long lifetime is guaranteed by the absence of lower dimensional operators (of light particles) couple to the X. We briefly discuss a possible explanation for the recently observed ultra-high-energy cosmic ray events by the decay of this unstable X particle.Comment: 9 pages, Late

Magneto-Acoustic Waves of Small Amplitude in Optically Thin Quasi-Isentropic Plasmas

The evolution of quasi-isentropic magnetohydrodynamic waves of small but finite amplitude in an optically thin plasma is analyzed. The plasma is assumed to be initially homogeneous, in thermal equilibrium and with a straight and homogeneous magnetic field frozen in. Depending on the particular form of the heating/cooling function, the plasma may act as a dissipative or active medium for magnetoacoustic waves, while Alfven waves are not directly affected. An evolutionary equation for fast and slow magnetoacoustic waves in the single wave limit, has been derived and solved, allowing us to analyse the wave modification by competition of weakly nonlinear and quasi-isentropic effects. It was shown that the sign of the quasi-isentropic term determines the scenario of the evolution, either dissipative or active. In the dissipative case, when the plasma is first order isentropically stable the magnetoacoustic waves are damped and the time for shock wave formation is delayed. However, in the active case when the plasma is isentropically overstable, the wave amplitude grows, the strength of the shock increases and the breaking time decreases. The magnitude of the above effects depends upon the angle between the wave vector and the magnetic field. For hot (T > 10^4 K) atomic plasmas with solar abundances either in the interstellar medium or in the solar atmosphere, as well as for the cold (T < 10^3 K) ISM molecular gas, the range of temperature where the plasma is isentropically unstable and the corresponding time and length-scale for wave breaking have been found.Comment: 14 pages, 10 figures. To appear in ApJ January 200

Machine learning-based prediction of tear osmolarity for contact lens practice

Purpose: This study addressed the utilisation of machine learning techniques to estimate tear osmolarity, a clinically significant yet challenging parameter to measure accurately. Elevated tear osmolarity has been observed in contact lens wearers and is associated with contact lens‐induced dry eye, a common cause of discomfort leading to discontinuation of lens wear. Methods: The study explored machine learning, regression and classification techniques to predict tear osmolarity using routine clinical parameters. The data set consisted of 175 participants, primarily healthy subjects eligible for soft contact lens wear. Various clinical assessments were performed, including symptom assessment with the Ocular Surface Disease Index and 5‐Item Dry Eye Questionnaire (DEQ‐5), tear meniscus height (TMH), tear osmolarity, non‐invasive keratometric tear film break‐up time (NIKBUT), ocular redness, corneal and conjunctival fluorescein staining and Meibomian glands loss. Results : The results revealed that simple linear regression was insufficient for accurate osmolarity prediction. Instead, more advanced regression models achieved a moderate level of predictive power, explaining approximately 32% of the osmolarity variability. Notably, key predictors for osmolarity included NIKBUT, TMH, ocular redness, Meibomian gland coverage and the DEQ‐5 questionnaire. In classification tasks, distinguishing between low (&lt;299 mOsmol/L), medium (300–307 mOsmol/L) and high osmolarity (&gt;308 mOsmol/L) levels yielded an accuracy of approximately 80%. Key parameters for classification were similar to those in regression models, emphasising the importance of NIKBUT, TMH, ocular redness, Meibomian glands coverage and the DEQ‐5 questionnaire. Conclusions: This study highlights the potential benefits of integrating machine learning into contact lens research and practice. It suggests the clinical utility of assessing Meibomian glands and NIKBUT in contact lens fitting and follow‐up visits. Machine learning models can optimise contact lens prescriptions and aid in early detection of conditions like dry eye, ultimately enhancing ocular health and the contact lens wearing experience

A U(3)_C X U(3)_L X U(3)_R gauge symmetry from intersecting D-branes

A three-family non-supersymmetric model with U(3)^3 gauge symmetry is analyzed in the context of intersecting D-branes. This is equivalent to the `trinification' model extended by three U(1) factors which survive as global symmetries in the low energy effective model. The Standard Model fermions are accommodated in the three possible bifundamental multiplets represented by strings with endpoints attached on different brane-stacks of this particular setup. Further, a natural Quark-Lepton hierarchy is realized due to the existence of the additional abelian symmetriesComment: 10 page

Volume preserving multidimensional integrable systems and Nambu--Poisson geometry

In this paper we study generalized classes of volume preserving multidimensional integrable systems via Nambu--Poisson mechanics. These integrable systems belong to the same class of dispersionless KP type equation. Hence they bear a close resemblance to the self dual Einstein equation. All these dispersionless KP and dToda type equations can be studied via twistor geometry, by using the method of Gindikin's pencil of two forms. Following this approach we study the twistor construction of our volume preserving systems

Relaxed fine-tuning in models with non-universal gaugino masses

We study, in a bottom-up approach, the fine-tuning problem between soft SUSY breaking parameters and the $\mu$-term for the successful electroweak symmetry breaking in the minimal supersymmetric standard model. It is shown that certain nontrivial ratios between gaugino masses, that is non-universal gaugino masses, are necessary at the GUT scale, in order for the fine-tuning to be reduced above 10 % order. In addition, when all the gaugino masses should be regarded as independent ones in their origins, a small gluino mass $M_3 \lesssim 120$ GeV and a non-vanishing $A$-term $A_t \sim O(M_3)$ associated to top squarks are also required at the GUT scale as well as the non-universality. On the other hand, when we consider some UV theory, which fixes ratios of soft SUSY breaking parameters as certain values with the overall magnitude, heavier spectra are allowed. It is favored that the gluino and wino masses are almost degenerate at the weak scale, while wider region of bino mass is favorable.Comment: 17 pages, 29 figure

Anomaly cancellation in effective supergravity from the heterotic string with an anomalous U(1)

© 2019 The Author(s) We show that a choice of Pauli-Villars regulators allows the cancellation of all the conformal and chiral anomalies in an effective field theory from Z3 compactification of the heterotic string with two Wilson lines and an anomalous U(1)

Slepton pair production in e+e- collision in supersymmetric left-right model

The pair production of sleptons in electron-positron collisions is investigated in a supersymmetric left-right model. The cross section is found considerably larger than in the minimal supersymmetric version of the Standard Model (MSSM) because of more contributing graphs. A novel process is a doubly charged higgsino exchange in u-channel, which makes the angular distribution of the final state particles and the final state asymmetries to differ from those of the MSSM. It also allows for the flavour non-diagonal final states $\tilde e\tilde\mu$, $\tilde e\tilde\tau$ and $\tilde \mu\tilde\tau$, forbidden in the MSSM. These processes also give indirect information about neutrino mixings since they depend on the same couplings as the Majorana mass terms of the right-handed neutrinos.Comment: 13 pages + 4figures available upon request, HU-SEFT R 1993-1

Vibrational signature of broken chemical order in a GeS2 glass: a molecular dynamics simulation

Using density functional molecular dynamics simulations, we analyze the broken chemical order in a GeS$_2$ glass and its impact on the dynamical properties of the glass through the in-depth study of the vibrational eigenvectors. We find homopolar bonds and the frequencies of the corresponding modes are in agreement with experimental data. Localized S-S modes and 3-fold coordinated sulfur atoms are found to be at the origin of specific Raman peaks whose origin was not previously clear. Through the ring size statistics we find, during the glass formation, a conversion of 3-membered rings into larger units but also into 2-membered rings whose vibrational signature is in agreement with experiments.Comment: 11 pages, 8 figures; to appear in Phys. Rev.