5,715 research outputs found
Induced Action for Conformal Higher Spins from Worldline Path Integrals
Conformal higher spin (CHS) fields, despite being non unitary, provide a
remarkable example of a consistent interacting higher spin theory in flat space
background, that is local to all orders. The non-linear action is defined as
the logarithmically UV divergent part of a one-loop scalar effective action. In
this paper we take a particle model, that describes the interaction of a scalar
particle to the CHS background, and compute its path integral on the circle. We
thus provide a worldline representation for the CHS action, and rederive its
quadratic part. We plan to come back to the subject, to compute cubic and
higher vertices, in a future work.Comment: 24 pages, references added, minor typos correcte
Damped Topological Magnons in the Kagom\'{e}-Lattice Ferromagnets
We demonstrate that interactions can substantially undermine the
free-particle description of magnons in ferromagnets on geometrically
frustrated lattices. The anharmonic coupling, facilitated by the
Dzyaloshinskii-Moriya interaction, and a highly-degenerate two-magnon continuum
yield a strong, non-perturbative damping of the high-energy magnon modes. We
provide a detailed account of the effect for the ferromagnet on the
kagom\'e lattice and propose further experiments.Comment: 4.5 p + 4 figs main, 8 p + 16 figs supplemental, typos correcte
Exact renormalization group in Batalin--Vilkovisky theory
In this paper, inspired by the Costello's seminal work, we present a general
formulation of exact renormalization group (RG) within the Batalin-Vilkovisky
(BV) quantization scheme. In the spirit of effective field theory, the BV
bracket and Laplacian structure as well as the BV effective action (EA) depend
on an effective energy scale. The BV EA at a certain scale satisfies the BV
quantum master equation at that scale. The RG flow of the EA is implemented by
BV canonical maps intertwining the BV structures at different scales.
Infinitesimally, this generates the BV exact renormalization group equation
(RGE). We show that BV RG theory can be extended by augmenting the scale
parameter space R to its shifted tangent bundle T[1]R. The extra odd direction
in scale space allows for a BV RG supersymmetry that constrains the structure
of the BV RGE bringing it to Polchinski's form. We investigate the implications
of BV RG supersymmetry in perturbation theory. Finally, we illustrate our
findings by constructing free models of BV RG flow and EA exhibiting RG
supersymmetry in the degree -1 symplectic framework and studying the
perturbation theory thereof. We find in particular that the odd partner of
effective action describes perturbatively the deviation of the interacting RG
flow from its free counterpart.Comment: 52 pages, no figures, introduction thoroughly rewritten, two new
subsections adde
Closed-form weak localization magnetoconductivity in quantum wells with arbitrary Rashba and Dresselhaus spin-orbit interactions
We derive a closed-form expression for the weak localization (WL) corrections
to the magnetoconductivity of a 2D electron system with arbitrary Rashba
and Dresselhaus (linear) and (cubic) spin-orbit
interaction couplings, in a perpendicular magnetic field geometry. In a system
of reference with an in-plane axis chosen as the high spin-symmetry
direction at , we formulate a new algorithm to calculate the
three independent contributions that lead to WL. The antilocalization is
counterbalanced by the term associated with the spin-relaxation along
, dependent only on . The other term is generated by
two identical scattering modes characterized by spin-relaxation rates which are
explicit functions of the orientation of the scattered momentum. Excellent
agreement is found with data from GaAs quantum wells, where in particular our
theory correctly captures the shift of the minima of the WL curves as a
function of . This suggests that the anisotropy of the effective
spin relaxation rates is fundamental to understanding the effect of the SO
coupling in transport.Comment: 5 pages, 2 figure
Evaluating the AdS dual of the critical O(N) vector model
We argue that the AdS dual of the three dimensional critical O(N) vector
model can be evaluated using the Legendre transform that relates the generating
functionals of the free UV and the interacting IR fixed points of the boundary
theory. As an example, we use our proposal to evaluate the minimal bulk action
of the scalar field that it is dual to the spin-zero ``current'' of the O(N)
vector model. We find that the cubic bulk self interaction coupling vanishes.
We briefly discuss the implications of our results for higher spin theories and
comment on the bulk-boundary duality for subleading N.Comment: 17 pages, 1 figure, v2 references added, JHEP versio
Entanglement Content of Quantum Particle Excitations II. Disconnected Regions and Logarithmic Negativity
In this paper we study the increment of the entanglement entropy and of the (replica) logarithmic negativity in a zero-density excited state of a free massive bosonic theory, compared to the ground state. This extends the work of two previous publications by the same authors. We consider the case of two disconnected regions and find that the change in the entanglement entropy depends only on the combined size of the regions and is independent of their connectivity. We subsequently generalize this result to any number of disconnected regions. For the replica negativity we find that its increment is a polynomial with integer coefficients depending only on the sizes of the two regions. The logarithmic negativity turns out to have a more complicated functional structure than its replica version, typically involving roots of polynomials on the sizes of the regions. We obtain our results by two methods already employed in previous work: from a qubit picture and by computing four-point functions of branch point twist fields in finite volume. We test our results against numerical simulations on a harmonic chain and find excellent agreement
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