16129121
Spinning flavor branes and fermion pairing instabilities
We consider probe Dp-branes, p=3,5,7, in global AdS_5 x S^5, rotating along an internal direction in the S^5. These are dual to strongly interacting N=4 SYM on S^3 with massless fundamental flavours, in the presence of an R-symmetry chemical potential for flavour fermions. For massless, "AdS-filling" Dp-brane embeddings at zero temperature, we find an infinite set of threshold values of the chemical potential at which instabilities are triggered. The onset of instability is always preceded by metastability of the zero density state. From the onset values of the chemical potential, we infer that unstable directions favour a homogeneous condensate of a bilinear made from fermion harmonics, or Cooper pairing. We confirm this picture both numerically and analytically. The linearized analysis showing the appearance of instabilities involves a charged scalar in global AdS space coupled to a (large) constant background gauge potential. The resulting frequency space correlator of the fermion bilinear at strong coupling displays poles in the upper half plane. In contrast, the correlator at zero coupling exhibits Pauli blocking due to occupation of states below the Fermi level, but no instabilities. The end-point of the strong coupling instability is not visible in our setup.
17544914
Precision test of AdS/CFT in Lunin-Maldacena background
We obtain the solutions and explicitly calculate the energy for a class of two-spin semiclassical string states in the Lunin-Maldacena background. These configurations are the β-deformed versions of the folded string solutions in AdS5 × S5 background. They correspond to certain single trace operators in the = 1 superconformal β deformation of = 4 Yang-Mills. We calculate the one loop anomalous dimension for the dual single trace operators from the associated twisted spin chain with a general two-cut distribution of Bethe roots. Our results show a striking match between the two calculations. We demonstrate the natural identification of parameters on the two sides of the analysis, and explain the significance of the Virasoro constraint associated with the winding motion of semiclassical strings from the perspective of the spin chain solution.
59440238
Vacuum structure and flavor symmetry breaking in supersymmetric SO(nc) gauge theories
We determine the vacuum structure and phases of N=1 theories obtained via a 
mass \mu for the adjoint chiral superfield in N=2, SO(n_c) SQCD. For large 
number of flavors these theories have two groups of vacua. The first exhibits 
dynamical breaking of flavor symmetry \USp(2n_f) \to U(n_f) and arises as a 
relevant deformation of a non-trivial superconformal theory. These are in the 
confined phase. The second group, in an IR-free phase with unbroken flavor 
symmetry, is produced from a Coulomb branch singularity with Seiberg's dual 
gauge symmetry. In the large-\mu regime both groups of vacua are well-described 
by dual quarks and mesons, and dynamical symmetry breaking in the first group 
occurs via meson condensation. We follow the description of these vacua from 
weak to strong coupling and demonstrate a nontrivial agreement between the 
phases and the number of vacua in the two regimes. We construct the 
semiclassical monopole flavor multiplets and argue that their multiplicity is 
consistent with the number of N=1 vacua.
18863456
Out of Equilibrium Fields in Inflationary Dynamics. Density Fluctuations
The energy and time scales during the inflationary stage of the universe calls for an out of equilibrium quantum field treatment. Moreover, the high energy densities involved (∼1/g ∼ 1012) make necessary the use of non-perturbative approaches as the large N and Hartree methods. We start these lectures by introducing the such non-perturbative out of equilibrium methods in cosmological universes. We discuss the renormalization procedure and the choice of initial conditions. We then study with these methods the non-linear dynamics of quantum fields in matter and radiation dominated FRW and de Sitter universes. For a variety of initial conditions, we compute the evolution of the inflaton, its quantum fluctuations and the equation of state. We investigate the phenomenon of explosive particle production due to spinodal instabilities and parametric amplification in FRW and de Sitter universes with and without symmetry breaking. We find that the particle production is somewhat sensitive to the expansion of the universe. In the large N limit for symmetry breaking scenarios, we determine generic late time fields behavior for any flat FRW and de Sitter cosmology. We find that quantum fluctuations damp in FRW as the square of the scale factor while the order parameter approaches a minimum of the potential at the same rate. We present a complete and numerically accessible renormalization scheme for the equation of motion and the energy momentum tensor in flat cosmologies. In this scheme the renormalization constants are independent of time and of the initial conditions. Furthermore, we consider an O(N) inflaton model coupled self-consistently to gravity in the semiclassical approximation, where the field is subject to ‘new inflation’ type initial conditions. We study the dynamics self-consistently and non-perturbatively with non-equilibrium field theory methods in the large N limit. We find that spinodal instabilities drive the growth of non-perturbatively large quantum fluctuations which shut off the inflationary growth of the scale factor. We find that a very specific combination of these large fluctuations plus the inflaton zero mode assemble into a new effective field. This new field behaves classically and it is the object which actually rolls down. We show how this reinterpretation qualitatively saves the standard picture of how metric perturbations are generated during inflation and that the spinodal growth of fluctuations dominates the time dependence of the Bardeen variable for superhorizon modes during inflation. We compute the amplitude and index for the spectrum of scalar density and tensor perturbations and argue that in all models of this type the spinodal instabilities are responsible for a ‘red’ spectrum of primordial scalar density perturbations. The decoherence aspects and the quantum to classical transition through inflation are studied in detail by following the full evolution of the density matrix.
15505916
Exact Superpotentials from Matrix Models
Dijkgraaf and Vafa (DV) have conjectured that the exact superpotential for a large class of = 1 SUSY gauge theories can be extracted from the planar limit of a certain holomorphic matrix integral. We test their proposal against existing knowledge for a family of deformations of = 4 SUSY Yang-Mills theory involving an arbitrary polynomial superpotential for one of the three adjoint chiral superfields. Specifically, we compare the DV prediction for these models with earlier results based on the connection between SUSY gauge theories and integrable systems. We find complete agreement between the two approaches. In particular we show how the DV proposal allows the extraction of the exact eigenvalues of the adjoint scalar in the confining vacuum and hence computes all related condensates of the finite-N gauge theory. We extend these results to include Leigh-Strassler deformations of the = 4 theory.
5243610
Non-Abelian Vortices at Weak and Strong Coupling in Mass Deformed ABJM Theory
We find half-BPS vortex solitons, at both weak and strong coupling, in the = 6 supersymmetric mass deformation of ABJM theory with U(N) × U(N) gauge symmetry and Chern-Simons level k. The strong coupling gravity dual is obtained by performing a k quotient of the = 8 supersymmetric eleven dimensional supergravity background of Lin, Lunin and Maldacena corresponding to the mass deformed M2-brane theory. At weak coupling, the BPS vortices preserving six supersymmetries are found in the Higgs vacuum of the theory where the gauge symmetry is broken to U(1) × U(1). The classical vortex solitons break a colour-flavour locked global symmetry resulting in non-Abelian internal orientational moduli and a CP1 moduli space of solutions. At strong coupling and large k, upon reduction to type IIA strings, the vortex moduli space and its action are computed by a probe D0-brane in the dual geometry. The mass of the D0-brane matches the classical vortex mass. However, the gravity picture exhibits a six dimensional moduli space of solutions, a section of which can be identified as the CP1 we find classically, along with a Dirac monopole connection of strength k. It is likely that the extra four dimensions in the moduli space are an artifact of the strong coupling limit and of the supergravity approximation.
118517206
Boson stars in a theory of complex scalar fields coupled to the U(1) gauge field and gravity
We study boson shells and boson stars in a theory of a complex scalar field coupled to the gauge field and Einstein gravity with the potential . This could be considered either as a theory of a massive complex scalar field coupled to an electromagnetic field and gravity in a conical potential, or as a theory in the presence of a potential that is an overlap of a parabolic and conical potential. Our theory has a positive cosmological constant . Boson stars are found to come in two types, having either ball-like or shell-like charge density. We studied the properties of these solutions and also determined their domains of existence for some specific values of the parameters of the theory. Similar solutions have also been obtained by Kleihaus, Kunz, Laemmerzahl and List, in a V-shaped scalar potential.
16931053
CP-odd weak basis invariants and texture zeros
We construct the CP-odd weak basis invariants from the neutrino mass matrix in a weak basis, in which the charged lepton mass matrix is diagonal, and find the necessary and sufficient conditions for CP conservation. We study the interrelationships between different CP-odd weak basis invariants to examine their implications for the Dirac- and Majorana-type CP violating phases for the phenomenologically allowed Frampton-Glashow-Marfatia texture zero structures of the neutrino mass matrix.
116623275
Experimental study of nuclei in the vicinity of the 'island of inversion' through the fusion-evaporation reaction
We report the observation of high-spin states in nuclei in the vicinity of the 'island of inversion', populated via the {sup 18}O+{sup 18}O fusion reaction at an incident beam energy of 34 MeV. The fusion reaction mechanism circumvents the limitations of other reactions used so far to populate excited states in these nuclei. The level structures of {sup 33,34}P and {sup 33}S have been investigated and their level schemes were substantially extended. The intensities and branching ratios of the {gamma} transitions were measured. The observed {gamma} coincidence intensity anisotropy and polarization asymmetry were analyzed for a consistent assignment of the spins and parities of the nuclear levels. The 1876-keV transition in {sup 34}P that had an ambiguous multipolarity assignment has been confirmed to be a mixed transition. Truncated (1p-1h) shell model calculations within the 'sdpf' valence space were performed. These calculations reproduce the experimental excitation energies of {sup 34}P but fail to explain the observed mixing ratio for the 1876-keV transition.
118657389
Four zero texture fermion mass matrices in SO(10) GUT
We attempt the integration of the phenomenologically successful four zero texture of fermion mass matrices with the renormalizable SO(10) GUT. The resulting scenario is found to be highly predictive. Firstly, we examine the phenomenological implications of a class of the lepton mass matrices with parallel texture structures and obtain interesting constraints on the parameters of the charged lepton and the neutrino mass matrices. We combine these phenomenological constraints with the constraints obtained from SO(10) GUT to reduce the number of the free parameters and to further constrain the allowed ranges of the free parameters. The solar/atmospheric mixing angles obtained in this analysis are in fairly good agreement with the data.
118138182
Shock-driven hydrodynamic instability induced by particle seeding
We report an experimental observation of an instability in gas of constant density (air) with an initial non-uniform seeding of small droplets that develops as a planar shock wave passes through the gas-droplet mix. The seeding non-uniformity is produced by vertical injection of a slow-moving jet of air pre-mixed with glycol droplets into the test section of a shock tube, with the plane of the shock parallel to the axis of the jet. After the shock passage, we observe development of two counter-rotating vortices in the plane normal to that axis. The physical mechanism of the instability we observe is peculiar to multiphase flow, where the shock acceleration causes the second (embedded) phase to move with respect to the embedding medium. With sufficient seeding concentration, this leads to entrainment of the embedding phase that acquires a relative velocity dependent on the initial seeding, resulting in vortex formation in the flow.