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Zahra Rezaei

Publications and source records attributed to Zahra Rezaei.

17 recordsLinked to original sources

Muon Anomalous Magnetic Moment in Noncommutative Space-Time

The explanation of the muon anomalous magnetic moment ($μ$-AMM) requires new physics beyond the Standard Model. In this work, we investigate the effects of noncommutative space-time on the $μ$-AMM within the Seiberg-Witten map framework, analyzing both tree-level and loop-level diagrams. Additionally, we examine the $μ$-AMM by studying the scattering cross-section of electron-positron annihilation into muon-antimuon pairs $ (e^- e^+ \rightarrow μ^- μ^+ ) $. Previous studies have explored the implications of noncommutative space-time through various processes, leading to different bounds on the noncommutative parameter $θ^{μν}$. Our analysis estimates $θ^{μν} \sim (43 \, \mathrm TeV)^{-2} $ for both tree-level and loop-level contributions when noncommutative space-time accounts for the entire observed $μ$-AMM. If noncommutative effects are responsible for only 10$\%$ of the $μ$-AMM, the constraint relaxes to approximately $(136 \, \mathrm TeV)^{-2}$. Furthermore, by comparing the noncommutative cross-section of $ e^- e^+ \rightarrow μ^- μ^+ $ with experimental data, we derive an approximate bound of $(90 \, \mathrm TeV)^{-2}$ which corresponds to a 23$\%$ contribution to the $μ$-AMM.

hep-ph

Preset-Voice Matching for Privacy Regulated Speech-to-Speech Translation Systems

In recent years, there has been increased demand for speech-to-speech translation (S2ST) systems in industry settings. Although successfully commercialized, cloning-based S2ST systems expose their distributors to liabilities when misused by individuals and can infringe on personality rights when exploited by media organizations. This work proposes a regulated S2ST framework called Preset-Voice Matching (PVM). PVM removes cross-lingual voice cloning in S2ST by first matching the input voice to a similar prior consenting speaker voice in the target-language. With this separation, PVM avoids cloning the input speaker, ensuring PVM systems comply with regulations and reduce risk of misuse. Our results demonstrate PVM can significantly improve S2ST system run-time in multi-speaker settings and the naturalness of S2ST synthesized speech. To our knowledge, PVM is the first explicitly regulated S2ST framework leveraging similarly-matched preset-voices for dynamic S2ST tasks.

cs.CL

Singlet scalar dark matter in the non-commutative space-time: a viable hypothesis to explain the gamma-ray excess in the galactic center

We explore the non-commutative space-time to revive the idea that gamma-ray excess in the galactic center can be the result of particle dark matter annihilation. In the non-commutative theory, the photon spectrum is produced by direct emission during this annihilation where a photon can be embed in the final state together with other direct products in new vertices. In the various configurations of dark matter phenomenology, we adopt the most common model known as singlet scalar. Calculating the relevant aspects of the model, we can obtain the photon flux in the galactic center. Comparing our numerical achievements with experimental data reveals that non-commutative space-time can be a reliable framework to explain the gamma-ray excess.

hep-ph

Throughput Optimization for Wireless Powered Interference Channels

This paper studies a general multi-user wireless powered interference channel (IFC) under the harvest-then-transmit protocol, where the communication in channel coherence time consists of two phases, namely wireless energy transfer (WET) and wireless information transfer (WIT). In the first phase, all energy transmitters (ETs) transmit energy signals to information transmitters (ITs) via collaborative waveform design, while in the second phase, each IT transmits an information signal to its intended ET using the harvested energy in the previous phase. The aim is to jointly design the WET-WIT time allocation, the (deterministic) transmit signal at the first phase, and the transmit power of ITs in the second phase to optimize the network throughput. The design problems are non-convex and hence difficult to solve globally. To deal with them, we propose efficient iterative algorithms based on alternating projections; then, the majorization-minimization technique is used to tackle the nonconvex sub-problems in each iteration. We also extend the devised design methodology by considering imperfect channel state information (CSI) and non-linearity in energy harvesting circuit. The proposed algorithms are locally convergent and can provide high-quality suboptimal solutions to the design problems. Simulation results show the effectiveness of the proposed algorithms under various setups.

eess.SP

The LHC Drell-Yan Measurements as a Constraint for the Noncommutative Space-Time

The LHC measurements of the differential cross section of the Drell-Yan process is used to constrain the noncommutative space-time (NCST) phase space. A $χ^2$ method is utilized to exclude the part of the parameters space which is not consistent with the LHC measurements. Depending on other NCST parameters, the scale can be pushed up to $Λ_{NC} > 655$ GeV. The effect of other parameters is also investigated. To our knowledge, it is the first time that a detailed statistical analysis is performed to compare the NCST results with the Hadron Collider measurements.

hep-ph

Optimal Energy Beamforming under Per-Antenna Power Constraint

Energy beamforming (EB) is a key technique to enhance the efficiency of wireless power transfer (WPT). In this paper, we study the optimal EB under per-antenna power constraint (PAC) which is more practical than the conventional sum-power constraint (SPC). We consider a multi antenna energy transmitter (ET) with PAC that broadcasts wireless energy to multiple randomly placed energy receivers (ER)s within its cell area. We consider sum energy maximization problem with PAC and provide the optimal solution structure for the general case. This optimal structure implies that sending one energy beam is optimal under PAC which means that the rank of transmit covariance matrix is one similar to SPC. We also derive closed-form solutions for two special cases and propose two sub-optimal solutions for general case, which performs very close to optimal beamforming.

cs.IT

Instability in Reaction-Superdiffusion Systems

We study the effect of superdiffusion on the instability in reaction-diffusion systems. It is shown that reaction-superdiffusion systems close to a Turing instability are equivalent to a time-dependent Ginzburg-Landau model and the corresponding free energy is introduced. This generalized free energy which depends on the superdiffusion exponent governs the stability, dynamics and the fluctuations of reaction-superdiffusion systems near the Turing bifurcation. In addition, we show that for a general n-component reaction-superdiffusion system, a fractional complex Ginzburg- Landau equation emerges as the amplitude equation near a Hopf instability. Numerical simulations of this equation are carried out to illustrate the effect of superdiffusion on spatio-temporal patterns. Finally the effect of superdiffusion on the instability in Brusselator model, as a special case of reaction-diffusion systems, is studied. In general superdiffusion introduces a new parameter that changes the behavior of the system near the instability.

nlin.PS

Meson Thermalization by Baryon Injection in D4/D6 Model

We study meson thermalization in a strongly coupled plasma of quarks and gluons using AdS/CFT duality technique. Four dimensional large-Nc QCD is considered as a theory governing this quark-gluon plasma (QGP) and D4/D6- brane model is chosen to be its holographic dual theory. In order to investigate meson thermalization, we consider a time-dependent change of baryon number chemical potential. Thermalization in gauge theory side corresponds to horizon formation on the probe flavor brane in the gravity side. The gravitational dual theory is compactified on a circle that the inverse of its radius is proportional to energy scale of dual gauge theory. It is seen that increase of this energy scale results in thermalization time dilation. In addition we study the effect of magnetic field on meson thermalization. It will be seen that magnetic field also prolongs thermalization process by making mesons more stable.

hep-th

Nucleon structure functions in noncommutative space-time

In the context of noncommutative space-time, we investigate the nucleon structure functions which plays an important role to identify the internal structure of nucleons. We use the corrected vertices and employ new vertices that appear in two approaches of noncommutativity and calculate the proton structure functions in terms of noncommutative tensor θ_{μν}. To check our result, we plot the nucleon structure function (NSF), F_2(x), and compare it with experimental data and the result coming out from the GRV, GJR and CT10 parametrization models. We show that new vertex which is arising the noncommutativity correction will lead us to better consistency between theoretical result and experimental data for NSF. This consistency would be better at small values of x-Bjorken variable. To indicate and confirm the validity of our calculations, we also act conversely and obtain an lower bound for the numerical values of Λ_{NC} scale which are corresponding to the recent reports.

hep-ph

Hydrodynamic Waves in an Anomalous Charged Fluid

We study the collective excitations in a relativistic fluid with an anomalous $U(1)$ current. In $3+1$ dimensions at zero chemical potential, in addition to ordinary sound modes we find two propagating modes in presence of an external magnetic field. The first one which is a transverse degenerate mode, propagates with a velocity proportional to the coefficient of gravitational anomaly; this is in fact the Chiral Alfvén wave recently found in \cite{Yamamoto:2015ria}. Another one is a wave of density perturbation, namely a chiral magnetic wave (CMW). The velocity dependence of CMW on the chiral anomaly coefficient is well known. We compute the dependence of CMW's velocity on the coefficient of gravitational anomaly as well. We also show that the dissipation splits the degeneracy of CAW. At finite chiral charge density we show that in general there may exist five chiral hydrodynamic waves. Of these five waves, one is the CMW while the other four are mixed Modified Sound-Alfvén waves. It turns out that in propagation transverse to the magnetic field no anomaly effect appear while in parallel to the magnetic field we find sound waves become dispersive due to anomaly.

hep-th

Algebraic Form of M3-Brane Action

We reformulate the bosonic action of unstable M3-brane to manifest its algebraic representation. It is seen that in contrast with string and M2-brane actions that are represented only in terms of two and three dimensional Lie-algebras respectively, the algebraic form of M3-brane action is a combination of four, three and two dimensional Lie-algebras. Corresponding brackets appear as mixtures of tachyon field, space-time coordinates, $X$, two-form field, $\hatω^{(2)}$, and Born-Infeld one-form, $\hat{b}_μ$.

hep-th

The effect of Dirac phase on acoustic vortex in media with screw dislocation

We study acoustic vortex in media with screw dislocation using the Katanaev-Volovich theory of defects. It is shown that the screw dislocation affects the beam's orbital angular momentum and changes the acoustic vortex strength. This change is a manifestation of topological Dirac phase and is robust against fluctuations in the system.

cond-mat.other

Boundary Super-Deformations, Boundary States, and Tachyon Condensation

The open string tachyon and U(1) gauge field as longitudinal fluctuations and the velocity as transverse fluctuation of an arbitrary dimensional D-brane are considered as boundary deformations of a closed superstring free action. The path integral approach will be applied to calculate the corresponding generalized boundary states using supersymmetrized boundary actions. Obtaining the disk partition functions from the boundary states and studying the effect of tachyon condensation on both of them in the NSNS and RR sectors, leads to results that differ from the established ones.

hep-th

Interaction of Moving Branes with Background Massless and Tachyon Fields in Superstring Theory

Using the boundary state formalism we study a moving D$p$-brane in a partially compact spacetime in the presence of the background fields: Kalb-Ramond $B_{μν}$, a U(1) gauge field $A_α$ and the tachyon field. The boundary state enables us to obtain interaction amplitude of two branes with above background fields. The branes are parallel or perpendicular to each other. Presence of the background fields, compactification of some directions of the spacetime, motion of the branes and arbitrariness of the branes' dimensions give a general feature to the system. Due to the tachyon fields and velocities of the branes, the behavior of the interaction amplitude reveals obvious differences from what is conventional.

hep-th

Moving Branes with Background Massless and Tachyon Fields in the Compact Spacetime

In this article we shall obtain the boundary state associated with a moving $Dp$-brane in the presence of the Kalb-Ramond field $B_{μν}$, an internal U(1) gauge field $A_α$ and a tachyon field, in the compact spacetime. According to this state, properties of the brane and a closed string, with mixed boundary conditions emitted from it, will be obtained. Using this boundary state we calculate the interaction amplitude of two moving $Dp_{1}$ and $Dp_{2}$-branes with above background fields in a partially compact spacetime. They are parallel or perpendicular to each other. Properties of the interaction amplitude will be analyzed and contribution of the massless states to the interaction will be extracted.

hep-th

Moving Branes in Presence of the Background Tachyon Fields

We compute the boundary state associated with a moving D$p$-brane in the presence of the open string tachyon field as a background field. The effect of the tachyon condensation on the boundary state will be discussed. It leads to a boundary state associated with a lower dimensional moving D-brane or a stationary instantonic D-brane. The former originates from condensation along the spatial directions and the latter comes from the temporal direction of the D-brane's worldvolume. Using the boundary state we also study the interaction amplitude between two arbitrary D$p_1$ and D$p_2$-branes. The long range behavior of the amplitude is investigated which shows an obvious deviation from the conventional form, due to the presence of the background tachyon field.

hep-th

Primordial vorticity and gradient expansion

The evolution equations of the vorticities of the electrons, ions and photons in a pre-decoupling plasma are derived, in a fully inhomogeneous geometry, by combining the general relativistic gradient expansion and the drift approximation within the Adler-Misner-Deser decomposition. The vorticity transfer between the different species is discussed in this novel framework and a set of general conservation laws, connecting the vorticities of the three-component plasma with the magnetic field intensity, is derived. After demonstrating that a source of large-scale vorticity resides in the spatial gradients of the geometry and of the electromagnetic sources, the total vorticity is estimated to lowest order in the spatial gradients and by enforcing the validity of the momentum constraint. By acknowledging the current bounds on the tensor to scalar ratio in the (minimal) tensor extension of the $Λ$CDM paradigm the maximal comoving magnetic field induced by the total vorticity turns out to be, at most, of the order of $10^{-37}$ G over the typical comoving scales ranging between 1 and 10 Mpc. While the obtained results seem to be irrelevant for seeding a reasonable galactic dynamo action, they demonstrate how the proposed fully inhomogeneous treatment can be used for the systematic scrutiny of pre-decoupling plasmas beyond the conventional perturbative expansions.

astro-ph.CO