Nucleon-Nucleon Scattering in a Strong External Magnetic Field and the Neutrino Emissivity

The nucleon-nucleon scattering in a large magnetic background is considered to find its potential to change the neutrino emissivity of the neutron stars. For this purpose we consider the one-pion-exchange approximation to find the NN cross-section in a background field as large as $10^{15}\texttt{G}-10^{18}\texttt{G}$. We show that the NN cross-section in neutron stars with temperatures in the range 0.1-5 \texttt{MeV} can be changed up to the one order of magnitude with respect to the one in the absence of the magnetic field. In the limit of the soft neutrino emission the neutrino emissivity can be written in terms of the NN scattering amplitude therefore the large magnetic fields can dramatically change the neutrino emissivity of the neutron stars as well.Comment: 21 pages, 5 figures, to appear in PR

Multiphysics discovery with moving boundaries using Ensemble SINDy and Peridynamic Differential Operator

This study proposes a novel framework for learning the underlying physics of phenomena with moving boundaries. The proposed approach combines Ensemble SINDy and Peridynamic Differential Operator (PDDO) and imposes an inductive bias assuming the moving boundary physics evolve in its own corotational coordinate system. The robustness of the approach is demonstrated by considering various levels of noise in the measured data using the 2D Fisher-Stefan model. The confidence intervals of recovered coefficients are listed, and the uncertainties of the moving boundary positions are depicted by obtaining the solutions with the recovered coefficients. Although the main focus of this study is the Fisher-Stefan model, the proposed approach is applicable to any type of moving boundary problem with a smooth moving boundary front without a mushy region. The code and data for this framework is available at: https://github.com/alicanbekar/MB_PDDO-SINDy.Comment: 26 pages, 22 figures, submitted to Proceedings of the Royal Society

Positronium Hyperfine Splitting in Non-commutative Space at the Order α6\alpha^6

We obtain positronium Hyperfine Splitting owing to the non-commutativity of space and show that, in the leading order, it is proportional to $\theta \alpha^6$ where, $\theta$ is the parameter of non-commutativity. It is also shown that spatial non-commutativity splits the spacing between $n=2$ triplet excited levels $E(2^3S_1)\to E(2^3P_2)$ which provides an experimental test on the non-commutativity of space.Comment: 7 pages, 2 figures, to appear in Phys. Rev.

Generation of circular polarization of the CMB

According to the standard cosmology, near the last scattering surface, the photons scattered via Compton scattering are just linearly polarized and then the primordial circular polarization of the CMB photons is zero. In this work we show that CMB polarization acquires a small degree of circular polarization when a background magnetic field is considered or the quantum electrodynamic sector of standard model is extended by Lorentz-noninvariant operators as well as noncommutativity. The existence of circular polarization for the CMB radiation may be verified during future observation programs and it represents a possible new channel for investigating new physics effects.Comment: 28 pages, v3, Phys. Rev. D 81, 084035 (2010

The effect of loading rate on fracture energy of asphalt mixture at intermediate temperatures and under different loading modes

At intermediate service temperatures hot mix asphalt (HMA) concretely are subjected to different loading rates due to movement of vehicles which can significantly affect their mechanical characteristics and final service load. Hence, in this paper the effect of loading rate on intermediate temperature fracture resistance of HMA materials is investigated experimentally in different modes of cracking. Different hot mix asphalt mixtures made of various compositions were subjected to asymmetric threepoint bend loading in the form of edge cracked semi-circular bend (SCB) specimens. The effect of aggregate type and air void were studied on the fracture energy values for three mode mixities (including pure mode I, mixed mode I/II and pure mode II) and at different temperatures of 5°C, 15°C and 25°C. Trends of change in fracture energy values revealed noticeable influence of loading rate on the low and intermediate temperature cracking behavior of tested asphalt mixtures with different air void contents and aggregate types subjected to mixed mode I/II loading. Also, a change observed in fracture resistance of asphalt mixtures at nearly zero (5°C) and intermediate temperatures (25°C) that was due to change in the behavior of bitumen from elastic to viscoelastic. © 2018, Gruppo Italiano Frattura. All rights reserved

Neutrino-electron scattering in noncommutative space

Neutral particles can couple with the $U(1)$ gauge field in the adjoint representation at the tree level if the space-time coordinates are noncommutative (NC). Considering neutrino-photon coupling in the NC QED framework, we obtain the differential cross section of neutrino-electron scattering. Similar to the magnetic moment effect, one of the NC terms is proportional to $\frac 1 T$, where $T$ is the electron recoil energy. Therefore, this scattering provides a chance to achieve a stringent bound on the NC scale in low energy by improving the sensitivity to the smaller electron recoil energy.Comment: 12 pages, 2 figure

Constraining noncommutative field theories with holography

An important window to quantum gravity phenomena in low energy noncommutative (NC) quantum field theories (QFTs) gets represented by a specific form of UV/IR mixing. Yet another important window to quantum gravity, a holography, manifests itself in effective QFTs as a distinct UV/IR connection. In matching these two principles, a useful relationship connecting the UV cutoff $\Lambda_{\rm UV}$, the IR cutoff $\Lambda_{\rm IR}$ and the scale of noncommutativity $\Lambda_{\rm NC}$, can be obtained. We show that an effective QFT endowed with both principles may not be capable to fit disparate experimental bounds simultaneously, like the muon $g-2$ and the masslessness of the photon. Also, the constraints from the muon $g-2$ preclude any possibility to observe the birefringence of the vacuum coming from objects at cosmological distances. On the other hand, in NC theories without the UV completion, where the perturbative aspect of the theory (obtained by truncating a power series in $\Lambda_{\rm NC}^{-2}$) becomes important, a heuristic estimate of the region where the perturbative expansion is well-defined $E/ \Lambda_{\rm NC} \lesssim 1$, gets affected when holography is applied by providing the energy of the system $E$ a $\Lambda_{\rm NC}$-dependent lower limit. This may affect models which try to infer the scale $\Lambda_{\rm NC}$ by using data from low-energy experiments.Comment: 4 pages, version to be published in JHE

Three Body Bound State in Non-Commutative Space

The Bethe-Salpeter equation in non-commutative QED (NCQED) is considered for three-body bound state. We study the non-relativistic limit of this equation in the instantaneous approximation and derive the corresponding Schr\"{o}dinger equation in non-commutative space. It is shown that the experimental data for Helium atom puts an upper bound on the magnitude of the parameter of non-commutativity, $\theta\sim10^{-9}\lambda_e^2$.Comment: 10 pages, 3 figures, to appear in Phys. Rev.

Direct Integration and Non-Perturbative Effects in Matrix Models

We show how direct integration can be used to solve the closed amplitudes of multi-cut matrix models with polynomial potentials. In the case of the cubic matrix model, we give explicit expressions for the ring of non-holomorphic modular objects that are needed to express all closed matrix model amplitudes. This allows us to integrate the holomorphic anomaly equation up to holomorphic modular terms that we fix by the gap condition up to genus four. There is an one-dimensional submanifold of the moduli space in which the spectral curve becomes the Seiberg--Witten curve and the ring reduces to the non-holomorphic modular ring of the group $\Gamma(2)$. On that submanifold, the gap conditions completely fix the holomorphic ambiguity and the model can be solved explicitly to very high genus. We use these results to make precision tests of the connection between the large order behavior of the 1/N expansion and non-perturbative effects due to instantons. Finally, we argue that a full understanding of the large genus asymptotics in the multi-cut case requires a new class of non-perturbative sectors in the matrix model.Comment: 51 pages, 8 figure

Solving the Topological String on K3 Fibrations

We present solutions of the holomorphic anomaly equations for compact two-parameter Calabi-Yau manifolds which are hypersurfaces in weighted projective space. In particular we focus on K3-fibrations where due to heterotic type II duality the topological invariants in the fibre direction are encoded in certain modular forms. The formalism employed provides holomorphic expansions of topological string amplitudes everywhere in moduli space.Comment: 60 pages, 1 figure, With an appendix by Sheldon Kat