Dynamics of Fundamental Matter in N=2* Yang-Mills Theory

We study the dynamics of quenched fundamental matter in $\mathcal{N}=2^\ast$ supersymmetric large $N$ SU(N) Yang-Mills theory at zero temperature. Our tools for this study are probe D7-branes in the holographically dual $\mathcal{N}=2^\ast$ Pilch-Warner gravitational background. Previous work using D3-brane probes of this geometry has shown that it captures the physics of a special slice of the Coulomb branch moduli space of the gauge theory, where the $N$ constituent D3-branes form a dense one dimensional locus known as the enhancon, located deep in the infrared. Our present work shows how this physics is supplemented by the physics of dynamical flavours, revealed by the D7-branes embeddings we find. The Pilch-Warner background introduces new divergences into the D7-branes free energy, which we are able to remove with a single counterterm. We find a family of D7-brane embeddings in the geometry and discuss their properties. We study the physics of the quark condensate, constituent quark mass, and part of the meson spectrum. Notably, there is a special zero mass embedding that ends on the enhancon, which shows that while the geometry acts repulsively on the D7-branes, it does not do so in a way that produces spontaneous chiral symmetry breaking.Comment: 24 pages, 8 figures. Corrected typos, added comment about counterterm. To appear in JHE

Employee Engagement among Service Sector: An Indian Perspective

Employee engagement has swiftly become new paradigm in organisational studies over past few years. Employee engagement is a measurable degree of an employee's positive or negative emotional attachment to their job, associates and organization that profoundly influences their willingness to learn and perform at work. Having engaged employees has become crucial in present business scenario where organisations look to their employees to take initiatives, bring innovations and optimum solutions to their current needs. This study investigates both job and organisational engagement of employees from two different sectors in Kerala namely, banking and IT (Information Technology). The purpose of the study is to define various concepts of employee engagement in modern organisations. The current cross sectional survey reinforces previous literature followed by discussions, limitations and conclusions. Keywords: Employee Engagement, Organizational Citizenship Behaviour, Organisational Commitment

Populating the swampland: the case of U(1)^496 and E_8 x U(1)^248

For d=10 N=1 SUGRA coupled to d=10 N=1 SYM, anomaly cancellation places severe constraints on the allowed gauge groups. Besides the ones known to appear in string theory, only U(1)^496 and E_8 x U(1)^248 are allowed. There are no known theories of quantum gravity that reduce in some limit to these two last supergravity theories, and in this note I present some evidence that those quantum theories might not exist. The first observation is that, upon compactification, requring that the quantum theory possesses a moduli space with finite volume typically implies the existence of singularities where the 4d gauge group is enhanced, but for these two theories that gauge enhancement is problematic from the 10d point of view. I also point out that while these four supergravity theories present repulson-type singularities, the known mechanism that repairs those singularities for the first two - the non-Abelian enhancon - is not available for the last two theories. In short, these two supergravity theories might be too Abelian for their own good.Comment: 12 page

Flavor-symmetry Breaking with Charged Probes

We discuss the recombination of brane/anti-brane pairs carrying $D3$ brane charge in $AdS_5 \times S^5$. These configurations are dual to co-dimension one defects in the ${\cal N}=4$ super-Yang-Mills description. Due to their $D3$ charge, these defects are actually domain walls in the dual gauge theory, interpolating between vacua of different gauge symmetry. A pair of unjoined defects each carry localized $(2+1)$ dimensional fermions and possess a global $U(N)\times U(N)$ flavor symmetry while the recombined brane/anti-brane pairs exhibit only a diagonal U(N). We study the thermodynamics of this flavor-symmetry breaking under the influence of external magnetic field.Comment: 21 pages, 10 figure

Computational and Mathematical Modelling of the EGF Receptor System

This chapter gives an overview of computational and mathematical modelling of the EGF receptor system. It begins with a survey of motivations for producing such models, then describes the main approaches that are taken to carrying out such modelling, viz. differential equations and individual-based modelling. Finally, a number of projects that applying modelling and simulation techniques to various aspects of the EGF receptor system are described

The magnetic structure and field dependence of the cycloid phas mediating the spin reorientation transition in Ca₃Ru₂O₇

We report a comprehensive experimental investigation of the magnetic structure of the cycloidal phase in Ca3Ru2O7, which mediates the spin reorientation transition, and establishes its magnetic phase diagram. In zero applied field, single-crystal neutron diffraction data confirms the scenario deduced from an earlier resonant x-ray scattering study: between 46.7~K <T<49.0~K the magnetic moments form a cycloid in the a−b plane with a propagation wavevector of (δ,0,1) with δ≃0.025 and an ordered moment of about 1 μB, with the eccentricity of the cycloid evolving with temperature. In an applied magnetic field applied parallel to the b-axis, the intensity of the (δ,0,1) satellite peaks decreases continuously up to about μ0H≃5 T, above which field the system becomes field polarised. Both the eccentricity of the cycloid and the wavevector increase with field, the latter suggesting an enhancement of the anti−symmetric Dzyaloshinskii−Moriya interaction via magnetostriction effects. Transitions between the various low-temperature magnetic phases have been carefully mapped out using magnetometry and resistivity. The resulting phase diagram reveals that the cycloid phase exists in a temperature window that expands rapidly with increasing field, before transitioning to a polarised paramagnetic state at 5 T. High-field magnetoresistance measurements show that below T≃70 K the resistivity increases continuously with decreasing temperature, indicating the inherent insulating nature at low temperatures of our high-quality, untwinned, single-crystals. We discuss our results with reference to previous reports of the magnetic phase diagram of Ca3Ru2O7 that utilised samples which were more metallic and/or poly-domain

Magnetized Domain Walls in the Deconfined Sakai-Sugimoto Model at Finite Baryon Density

The magnetized pure pion gradient ($\mathcal{5}\phi$) phase in the deconfined Sakai-Sugimoto model is explored at zero and finite temperature. We found that the temperature has very small effects on the phase. The thermodynamical properties of the phase shows that the excitations behave like a scalar solitonic free particles. By comparing the free energy of the pion gradient phase to the competing multiquark-pion gradient (MQ-$\mathcal{5}\phi$) phase, it becomes apparent that the pure pion gradient is less thermodynamically preferred than the MQ-$\mathcal{5}\phi$ phase. However, in the parameter space where the baryonic chemical potential is smaller than the onset value of the multiquark, the dominating magnetized nuclear matter is the pion gradient phase.Comment: 20 pages, 9 figure

Magnetic structure and field dependence of the cycloid phase mediating the spin reorientation transition in Ca3Ru2 O7

We report a comprehensive experimental investigation of the magnetic structure of the cycloidal phase in Ca3Ru2O7, which mediates the spin reorientation transition and establishes its magnetic phase diagram. In zero applied field, single-crystal neutron diffraction data confirm the scenario deduced from an earlier resonant x-ray scattering study: For 46.7K <T< 49.0 K the magnetic moments form a cycloid in the a-b plane with a propagation wave vector of (δ,0,1) with δ≃0.025 and an ordered moment of about 1μB, with the eccentricity of the cycloid evolving with temperature. In an applied magnetic field applied parallel to the b axis, the intensity of the (δ,0,1) satellite peaks decreases continuously up to about μ0H≃5T, above which field the system becomes field polarized. Both the eccentricity of the cycloid and the wave vector increase with field, the latter suggesting an enhancement of the antisymmetric Dzyaloshinskii-Moriya interaction over the symmetric exchange interactions via magnetostriction effects. Transitions between the various low-temperature magnetic phases have been carefully mapped out using magnetometry and resistivity. The resulting phase diagram reveals that the cycloid phase exists in a temperature window that expands rapidly with increasing field, before transitioning to a polarized paramagnetic state at 5 T. High-field magnetoresistance measurements show that below T≃70K the resistivity increases continuously with decreasing temperature, indicating the inherent insulating nature at low temperatures of our high-quality, untwinned, single crystals. We discuss our results with reference to previous reports of the magnetic phase diagram of Ca3Ru2O7 that utilized samples which were more metallic and/or polydomain

Magnetic properties of holographic multiquarks in the quark-gluon plasma

We study the magnetic properties of the coloured multiquark states in the quark-gluon plasma where the gluons are deconfined and the chiral symmetry is still broken, using the Sakai-Sugimoto model. There are two possible magnetized multiquark configurations. Both configurations converge to the same configuration at the critical field and temperature before they dissociate altogether either into less coloured multiquarks or into other phases for a fixed density. It is also found that the multiquarks with higher colour charges respond more to the external magnetic field in both the magnetization and the degree of chiral symmetry breaking. Magnetic field also makes it more difficult for multiquark states with large colour charges to satisfy the equilibrium condition of the configuration in the gravity dual picture. As long as the chemical potential $\mu > \mu_{onset}$, the magnetized multiquarks phase is thermodynamically preferred over the magnetized vacuum. Pure pion gradient and the chiral-symmetric quark-gluon plasma ($\chi_S$-QGP) phase for the general Sakai-Sugimoto model are discussed and compared with the multiquark phase in the presence of the magnetic field. It is found that at large densities and moderate fields, the mixed phase of multiquarks and the pion gradient is thermodynamically preferred over the $\chi_S$-QGP.Comment: 26 pages, 16 figures, revised version with significant changes and extension to other magnetized nuclear phase

Thermal Dynamics of Quarks and Mesons in N=2* Yang-Mills Theory

We study the dynamics of quenched fundamental matter in $\mathcal{N}=2^\ast$ supersymmetric large $N_c$ $SU(N_c)$ Yang-Mills theory, extending our earlier work to finite temperature. We use probe D7-branes in the holographically dual thermalized generalization of the $\mathcal{N}=2^\ast$ Pilch-Warner gravitational background found by Buchel and Liu. Such a system provides an opportunity to study how key features of the dynamics are affected by being in a non-conformal setting where there is an intrinsic scale, set here by the mass, $m_H$, of a hypermultiplet. Such studies are motivated by connections to experimental studies of the quark-gluon plasma at RHIC and LHC, where the microscopic theory of the constituents, QCD, has a scale, $\Lambda_{\rm QCD}$. We show that the binding energy of mesons in the $\mathcal{N}=2^\ast$ theory is increased in the presence of the scale $m_H$, and that subsequently the meson-melting temperature is higher than for the conformal case.Comment: 17 pages, 6 figure