Operators with Large Quantum Numbers, Spinning Strings, and Giant Gravitons

We study the behaviour of spinning strings in the background of various distributions of smeared giant gravitons in supergravity. This gives insights into the behaviour of operators of high dimension, spin and R-charge. Using a new coordinate system recently presented in the literature, we find that it is particularly natural to prepare backgrounds in which the probe operators develop a variety of interesting new behaviours. Among these are the possession of orbital angular momentum as well as spin, the breakdown of logarithmic scaling of dimension with spin in the high spin regime, and novel splitting/fractionation processes.Comment: 22 pages, 9 figures, LaTe

Universality in the Large N_c Dynamics of Flavour: Thermal Vs. Quantum Induced Phase Transitions

We show how two important types of phase transition in large N_c gauge theory with fundamental flavours can be cast into the same classifying framework as the meson-melting phase transition. These are quantum fluctuation induced transitions in the presence of an external electric field, or a chemical potential for R-charge. The classifying framework involves the study of the local geometry of a special D-brane embedding, which seeds a self-similar spiral structure in the space of embeddings. The properties of this spiral, characterized by a pair of numbers, capture some key universal features of the transition. Computing these numbers for these non-thermal cases, we find that these transitions are in the same universality class as each other, but have different universal features from the thermal case. We present a natural generalization that yields new universality classes that may pertain to other types of transition.Comment: 22 pages, 4 figures, pdfLaTe

Global Currents, Phase Transitions, and Chiral Symmetry Breaking in Large N_c Gauge Theory

We study, using a gravity dual, the finite temperature dynamics of $SU(N_c)$ gauge theory for large $N_c$, with fundamental quark flavours in a quenched approximation, in the presence of a fixed R--charge under a global R--current. We observe several notable phenomena. There is a first order phase transition where the quark condensate jumps discontinuously at finite quark mass, generalizing similar transitions seen at zero charge. Our tool in these studies is holography, the string dual of the gauge theory being the geometry of $N_c$ spinning D3--branes at finite temperature, probed by a D7--brane.Comment: (corrected version that appeared in JHEP

Quarks in an External Electric Field in Finite Temperature Large N Gauge Theory

We use a ten dimensional dual string background to aspects of the physics large N four dimensional SU(N) gauge theory, where its fundamental quarks are charged under a background electric field. The theory is N=2 supersymmetric for vanishing temperature and electric field. At zero temperature, we observe that the electric field induces a phase transition associated with the dissociation of the mesons into their constituent quarks. This is an analogue of an insulator-metal transition, since the system goes from being an insulator with zero current (in the applied field) to a conductor with free charge carriers (the quarks). At finite temperature this phenomenon persists, with the dissociation transition become subsumed into the more familiar meson melting transition. Here, the dissociation phenomenon reduces the critical melting temperature.Comment: 20 pages, multiple figures. Corrected typo

Magnetic Catalysis in AdS4

We study the formation of fermion condensates in Anti de Sitter space. In particular, we describe a novel version of magnetic catalysis that arises for fermions in asymptotically AdS4 geometries which cap off in the infra-red with a hard wall. We show that the presence of a magnetic field induces a fermion condensate in the bulk that spontaneously breaks CP symmetry. From the perspective of the dual boundary theory, this corresponds to a strongly coupled version of magnetic catalysis in d=2+1.Comment: 22 pages, 4 figures. v2: References added, factors of 2 corrected, extra comments added in appendix. v3: extra comments about fermion modes in a hard wall background. v4: A final factor of

Dismantling monuments as the core of the post-2014 'decommunisation' in Ukraine and Poland

Drawing on a wide range of sources (Polish and Ukrainian legal acts, Russian and international media), this study looks at the 'monument fall' in Ukraine and Poland as part of the post-2014 memory wars. The purpose of this article is to identify the main patterns associated with the demolition of Soviet and Russian monuments in the two countries. The 'decommunisation' of public space is an element of Ukraine's and Poland's politics of memory, enshrined in legal acts. Its driving force is the Institutes of National Remembrance, whose priorities include dismantling Soviet and pre-revolutionary Russian monuments, which came into full swing after the beginning of Russia's special military operation to denazify and demilitarise Ukraine. The official narratives allot Poland and Ukraine the role of victims of 'two aggressors' in World War II, which found themselves under 'communist occupation'. Therefore, the politics of memory of the two countries seek to get rid of the 'Soviet legacy' as the legacy of the 'occupying country'. Whilst Poland pursues 'residual decommunisation' focused on dismantling the remaining memorials to Soviet soldiers-liberators, Ukraine is committed to transforming 'decommunisation' into full-scale 'derussification'. At the same time, the process of 're-Sovietisation/Sovietisation' has been launched in the liberated territories of Ukraine. It consists in restoring previously destroyed monuments or installing new ones

Universal Holographic Chiral Dynamics in an External Magnetic Field

In this work we further extend the investigation of holographic gauge theories in external magnetic fields, continuing earlier work. We study the phenomenon of magnetic catalysis of mass generation in 1+3 and 1+2 dimensions, using D3/D7- and D3/D5-brane systems, respectively. We obtain the low energy effective actions of the corresponding pseudo Goldstone bosons and study their dispersion relations. The D3/D7 system exhibits the usual Gell-Mann--Oakes--Renner (GMOR) relation and a relativistic dispersion relation, while the D3/D5 system exhibits a quadratic non-relativistic dispersion relation and a modified linear GMOR relation. The low energy effective action of the D3/D5 system is related to that describing magnon excitations in a ferromagnet. We also study properties of general Dp/Dq systems in an external magnetic field and verify the universality of the magnetic catalysis of dynamical symmetry breaking.Comment: 41 pages, 11 figures, references adde

D3/D7 Quark-Gluon Plasma with Magnetically Induced Anisotropy

We study the effects of the temperature and of a magnetic field in the setup of an intersection of D3/D7 branes, where a large number of D7 branes is smeared in the transverse directions to allow for a perturbative solution in a backreaction parameter. The magnetic field sources an anisotropy in the plasma, and we investigate its physical consequences for the thermodynamics and energy loss of particles probing the system. In particular we comment on the stress-energy tensor of the plasma, the propagation of sound in the directions parallel and orthogonal to the magnetic field, the drag force of a quark moving through the medium and jet quenching.Comment: 29 pages + appendices, 5 figures. v2 Version to appear in JHEP, with minor revisions, references added and typos correcte

Dynamics of the chiral phase transition from AdS/CFT duality

We use Lorentzian signature AdS/CFT duality to study a first order phase transition in strongly coupled gauge theories which is akin to the chiral phase transition in QCD. We discuss the relation between the latent heat and the energy (suitably defined) of the component of a D-brane which lies behind the horizon at the critical temperature. A numerical simulation of a dynamical phase transition in an expanding, cooling Quark-Gluon plasma produced in a relativistic collision is carried out.Comment: 30 pages, 5 figure