arXiv subjects

Gianni Tallarita

Publications and source records attributed to Gianni Tallarita.

35 records · Page 2Linked to original sources

arXiv2015

Spin vortices in the Abelian-Higgs model with cholesteric vacuum structure

We continue the study of $U(1)$ vortices with cholesteric vacuum structure. A new class of solutions is found which represent global vortices of the internal spin field. These spin vortices are characterized by a non-vanishing angular dependence at spatial infinity, or winding. We show that despite the topological $\mathbb{Z}_2$ behavior of $SO(3)$ windings, the topological charge of the spin vortices is of the $\mathbb{Z}$ type in the cholesteric. We find these solutions numerically and discuss the properties derived from their low energy effective field theory in $1+1$ dimensions.

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arXiv2015

$SU(N)$ BPS Monopoles in $\mathcal{M}^2\times S^2$

We extend the investigation of BPS saturated t'Hooft-Polyakov monopoles in $\mathcal{M}^{2}\times S^{2}$ to the general case of $SU(N)$ gauge symmetry. This geometry causes the resulting $N-1$ coupled non-linear ordinary differential equations for the $N-1$ monopole profiles to become autonomous. One can also define a flat limit in which the curvature of the background metric is arbitrarily small but the simplifications brought in by the geometry remain. We prove analytically that non-trivial solutions in which the profiles are not proportional can be found. Moreover, we construct numerical solutions for $N=2,3$ and 4. The presence of the parameter $N$ allows one to take a smooth large $N$ limit which greatly simplifies the treatment of the infinite number of profile function equations. We show that, in this limit, the system of infinitely many coupled ordinary differential equations for the monopole profiles reduces to a single two-dimensional non-linear partial differential equation.

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arXiv2015

't Hooft-Polyakov Monopoles with Non-Abelian Moduli

We extend the Georgi-Glashow model of the t'Hooft-Polyakov monopoles to include additional collective coordinates "orientational isospin moduli". The low-energy theory of these solitonic solutions can be interpreted as dyons with isospin.

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arXiv2015

Confining Strings in Supersymmetric Theories with Higgs Branches

We study flux tubes (strings) on the Higgs branches in supersymmetric gauge theories. In generic vacua on the Higgs branches strings were shown to develop long-range "tails" associated with massless fields, a characteristic feature of the Higgs branch (the only exception is the vacuum at the base of the Higgs branch). A natural infrared regularization for the above tails is provided by a finite string length L. We perform a numerical study of these strings in generic vacua. We focus on the simplest example of strings in N=1 supersymmetric QED with the Fayet-Iliopoulos term. In particular, we examine the accuracy of a logarithmic approximation (proposed earlier by Evlampiev and Yung) for the tension of such string solutions. In the Evlampiev-Yung formula the dependence of tension on the string length is logarithmic and the dependence on the geodesic length from the base of the Higgs branch is quadratic. We observe a remarkable agreement of our numerical results for the string tension with the Evlampiev-Yung analytic expression.

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arXiv2014

Low energy dynamics of $U(1)$ vortices in systems with cholesteric vacuum structure

We discuss flux tubes in systems with $U(1)$ gauge, and spin-orbit locked $SO(3)_{S+L}$ symmetry. The spin-orbit locking is achieved explicitly in the Lagrangian by introducing a parity violating twist term which causes the spontaneous breaking of $SO(3)_{S+L} \rightarrow SO(2)$. Additionally, this term causes a spontaneous breaking of the translational symmetry along a particular direction. Thus, the system appears with a cholesteric vacuum under certain conditions of the parameter space. With this term, the system admits $U(1)$ topologically stable vortices with additional structure in the vortex cores. This added structure leads to additional moduli appearing in the low energy dynamics. We determine these solutions and their low energy theory.

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arXiv2014

Constraining Monopoles by Topology: an Autonomous System

We find both analytical and numerical solutions of SU(2) Yang-Mills with an adjoint Higgs field within both closed and open tubes whose sections are spherical caps. This geometry admits a smooth limit in which the space-like metric is flat and, moreover, allows one to use analytical tools which in the flat case are not available. Some of the analytic configurations, in the limit of vanishing Higgs coupling, correspond to magnetic monopoles and dyons living within this tube-shaped domain. However, unlike what happens in the standard case, analytical solutions can also be found in the case in which the Higgs coupling is non-vanishing. We further show that the system admits long-lived breathers.

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arXiv2014

Holographic Lifshitz Superconductors with an Axion Field

We use a Yang-Mills field coupled to an axion as probes of a black hole with arbitrary Lifshitz scaling to investigate, via holography, superconducting phase transitions of the dual theory with a $p_x+ip_y$ condensate. In the relativistic case with no axion, this phase is known to be unstable, the stable phase corresponding to condensates of the $p_x$ form. We investigate this stability in theories with non-relativistic scaling. Finally we numerically compute the "Hall" conductivity of these black holes in the non superconducting phase as a function of their Lifshitz scaling.

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arXiv2014

More on the Abrikosov Strings with Non-Abelian Moduli

We continue explorations of deformed Abrikosov-Nielsen-Olesen (ANO) strings, with non-Abelian moduli on the world sheet. In a simple model with an extra field we find classically stable ANO and non-Abelian strings. The tension of the latter is a few percent lower than the tension of the ANO string. Then we calculate the interpolating field configuration. Once the kink mass $M_k$ and the difference of tensions $ΔT$ are found we calculate the decay rate of the ANO string with a higher tension ("false vacuum") into the non-Abelian string with the lower tension ("genuine vacuum") through the "bubble" formation in the quasiclassical approximation.

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arXiv2012

Lifshitz holography with a probe Yang-Mills field

Taking as a probe an SU(2) gauge field with Yang-Mills action in a 3+1 dimensional Lifshitz black hole background, we use the gauge/gravity correspondence to discuss finite temperature effects in the dual theory defined on the boundary. In order to test the dependence of results on the anisotropic scaling exponent z we consider two analytical black hole solutions with z=2 and z=4. Apart from solving the equations of motion in the bulk using a numerical approach, we also apply an analytical approximation allowing the determination of the phase transition character, the critical exponent and the critical temperature behavior as a function of z.

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arXiv2012

Gauged Lifshitz model with Chern-Simons term

We present a gauged Lifshitz Lagrangian including second and forth order spatial derivatives of the scalar field and a Chern-Simons term, and study non-trivial solutions of the classical equations of motion. While the coefficient beta of the forth order term should be positive in order to guarantee positivity of the energy, the coefficient alpha of the quadratic one need not be. We investigate the parameter domains finding significant differences in the field behaviors. Apart from the usual vortex field behavior of the ordinary relativistic Chern-Simons-Higgs model, we find in certain parameter domains oscillatory solutions reminiscent of the modulated phases of Lifshitz systems.

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arXiv2012

Super-Higgs in Superspace

We determine the effective gravitational couplings in superspace whose components reproduce the supergravity Higgs effect for the constrained Goldstino multiplet. It reproduces the known Gravitino sector whilst constraining the off-shell completion. We show that these components arise by computing the effective action. This may be useful for phenomenological studies and model building: We give an example of its application to multiple Goldstini.

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arXiv2011

AdS Phase Transitions at finite κ

We investigate the effect of adding a Chern-Simons term coupled to an axion field to SU(2) Einstein-Yang-Mills in a fixed $AdS_4$/Schwarzschild background. We show that, when the axion has no potential, there is a phase transition between a Reissner-Nordstrom black-hole and one with a non-abelian condensate as per the vanishing Chern-Simons case. Furthermore, by giving the axion field a mass, one observes a phase transition between a Reissner-Nordstrom black-hole with axion hair to a "superconducting" phase which also has a non-trivial axion profile. We are able to perform a preliminary analysis for this interesting case and observe that we can shift the critical temperature at which the phase transition occurs and observe interesting features of the order parameter scaling form.

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arXiv2010

Maxwell-Chern-Simons Vortices and Holographic Superconductors

We investigate probe limit vortex solutions of a charged scalar field in Einstein-Maxwell theory in 3+1 dimensions, for an asymptotically AdS Schwarzschild black hole metric with the addition of an axionic coupling to the Maxwell field. We show that the inclusion of such a term, together with a suitable potential for the axion field, can induce an effective Chern-Simons term on the 2+1 dimensional boundary. We obtain numerical solutions of the equations of motion and find Maxwell-Chern-Simons like magnetic vortex configurations, where the magnetic field profile varies with the size of the effective Chern-Simons coupling. The axion field has a non-trivial profile inside the AdS bulk but does not condense at spatial infinity.

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arXiv2010

Non Abelian Geometrical Tachyon

We investigate the dynamics of a pair of coincident D5 branes in the background of $k$ NS5 branes. It has been proposed by Kutasov that the system with a single probing D-brane moving radially in this background is dual to the tachyonic DBI action for a non-BPS Dp brane. We extend this proposal to the non-abelian case and find that the duality still holds provided one promotes the radial direction to a matrix valued field associated with a non-abelian geometric tachyon and a particular parametrization for the transverse scalar fields is chosen. The equations of motion of a pair of coincident D5 branes moving in the NS5 background are determined. Analytic and numerical solutions for the pair are found in certain simplified cases in which the U(2) symmetry is broken to $U(1) \times U(1)$ corresponding to a small transverse separation of the pair. For certain range of parameters these solutions describe periodic motion of the centre of mass of the pair 'bouncing off' a finite sized throat whose minimum size is limited by the D5 branes separation.

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arXiv2010

Connection Constraints from Non-Abelian Supersymmetric Quantum Mechanics

We generalise the study of constraints imposed by supersymmetry on the Berry connection to transformations with component fields in representations of an internal symmetry group G. Since the fields act as co-ordinates of the underlying space one finds a non-trivial extension to its structure and, correspondingly, there are new non-abelian constraints on the Berry connection. The specific case of G=SU(2) is shown to constrain the connection to behave as a magnetic monopole over su(2), its Lie algebra.

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arXiv2009

Non Abelian Tachyon Kinks

Starting from the action of two coincident non-BPS D9-branes, we investigate kink configurations of the U(2) matrix tachyon field. We consider both Str and Tr prescriptions for the trace over gauge indices of the non-BPS action. Non-abelian tachyon condensation in the theory with Tr prescription, and the resulting fluctuations about the kink profile, are shown to give rise to a theory of two coincident BPS D8-branes. This is a natural non-abelian generalization of Sen's mechanism of tachyon condensation on a single non-BPS Dp-brane yielding a single BPS brane of codimesion one. By contrast, starting with the Str gauge trace prescription of the coincident non-BPS D9-brane action, such a generalization of Sen's mechanism appears problematic.

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arXiv2009

Dirac-Born-Infeld actions and Tachyon Monopoles

We investigate magnetic monopole solutions of the non-abelian DBI action describing 2 coincident non-BPS D9-branes in flat space. Just as in the case of kink and vortex solitonic tachyon solutions of the full DBI non-BPS actions, as previously analyzed by Sen, these monopole configurations are singular in the first instance and require regularization. We discuss a suitable non-abelian ansatz and show it solves the equations of motion to leading order in the regularization parameter. Fluctuations are studied and shown to describe a codimension 3 BPS D6-brane. A formula is derived for its tension. We comment on the implication to our results from both the trace (Tr) and symmetrized trace (Str) prescriptions of the non-abelian DBI action of coincident non-BPS D9-branes.

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