124 research outputs found
Two destructive effects of decoherence on Bell inequality violation
We consider a system of two spin-1/2 particles, initially in an entangled
Bell state. If one of the particles is interacting with an environment (e.g. a
collection of N independent spins), the two-particle system undergoes
decoherence. Using a simple model of decoherence, we show that this process has
two consequences. First, the maximal amount by which the CHSH inequality is
violated decays to zero. Second, the set of directions of measurement for which
the inequality is violated is reduced in the course of decoherence. The volume
of that set is bounded above by C|r|^2, where r is the decoherence factor. We
obtain similar results for the case when each of the two particles is in
interaction with a separate environment.Comment: v2: added results for decoherence due to interactions of both
particles + minor changes; v3: minor change
Manipulating magnetism and conductance of an adatom-molecule junction on metal surfaces: ab initio study
The state of the art ab initio calculations reveal the effect of a scanning
tunnelling microscopy tip on magnetic properties and conductance of a
benzene-adatom sandwich on Cu(001). We concentrate on a benzene-Co system
interacting with a Cr tip. Our studies give a clear evidence that magnetism and
conductance in molecule-adatom junctions can be tailored by the STM tip.
Varying the tip-substrate distance the magnetic moment of the Co adatom can be
switched on/off. The interplay between spin-polarized electron transport
through the junction and its magnetic properties is demonstrated. A spin-filter
effect in the junction is predicted.Comment: 4 pages, 3 figure
Quark--anti-quark potential in N=4 SYM
We construct a closed system of equations describing the quark--anti-quark
potential at any coupling in planar N=4 supersymmetric Yang-Mills theory. It is
based on the Quantum Spectral Curve method supplemented with a novel type of
asymptotics. We present a high precision numerical solution reproducing the
classical and one-loop string predictions very accurately. We also analytically
compute the first 7 nontrivial orders of the weak coupling expansion.
Moreover, we study analytically the generalized quark--anti-quark potential
in the limit of large imaginary twist to all orders in perturbation theory. We
demonstrate how the QSC reduces in this case to a one-dimensional Schrodinger
equation. In the process we establish a link between the Q-functions and the
solution of the Bethe-Salpeter equation.Comment: 31 pages, 1 figure; v2: minor correcton
Contour deformation trick in hybrid NLIE
The hybrid NLIE of AdS_5 x S^5 is applied to a wider class of states. We find
that the Konishi state of the orbifold AdS_5 x (S^5/Z_S) satisfies A_1 NLIE
with the source terms which are derived from contour deformation trick. For
general states, we construct a deformed contour with which the contour
deformation trick yields the correct source terms.Comment: 39 pages, 6 figures, v2: discussion on analyticity constraints
replaced by consistent deformed contou
Numerical results for the exact spectrum of planar AdS4/CFT3
We compute the anomalous dimension for a short single-trace operator in
planar ABJM theory at intermediate coupling. This is done by solving
numerically the set of Thermodynamic Bethe Ansatz equations which are expected
to describe the exact spectrum of the theory. We implement a truncation method
which significantly reduces the number of integral equations to be solved and
improves numerical efficiency. Results are obtained for a range of 't Hooft
coupling lambda corresponding to , where h(lambda) is
the interpolating function of the AdS4/CFT3 Bethe equations.Comment: v3: corrected Acknowledgements section; v4: minor changes, published
version; v5: fixed typos in Eq. (3.9
Quantum Spectral Curve at Work: From Small Spin to Strong Coupling in N=4 SYM
We apply the recently proposed quantum spectral curve technique to the study
of twist operators in planar N=4 SYM theory. We focus on the small spin
expansion of anomalous dimensions in the sl(2) sector and compute its first two
orders exactly for any value of the 't Hooft coupling. At leading order in the
spin S we reproduced Basso's slope function. The next term of order S^2
structurally resembles the Beisert-Eden-Staudacher dressing phase and takes
into account wrapping contributions. This expansion contains rich information
about the spectrum of local operators at strong coupling. In particular, we
found a new coefficient in the strong coupling expansion of the Konishi
operator dimension and confirmed several previously known terms. We also
obtained several new orders of the strong coupling expansion of the BFKL
pomeron intercept. As a by-product we formulated a prescription for the correct
analytical continuation in S which opens a way for deriving the BFKL regime of
twist two anomalous dimensions from AdS/CFT integrability.Comment: 53 pages, references added; v3: due to a typo in the coefficients C_2
and D_2 on page 29 we corrected the rational part of the strong coupling
predictions in equations (1.5-6), (6.22-24), (6.27-30) and in Table
Roadmap on Wilson loops in 3d Chern-Simons-matter theories
This is a compact review of recent results on supersymmetric Wilson loops in ABJ(M) and related theories. It aims to be a quick introduction to the state of the art in the field and a discussion of open problems. It is divided into short chapters devoted to different questions and techniques. Some new results, perspectives and speculations are also presented. We hope this might serve as a baseline for further studies of this topic
Generalized cusp in AdS_4 x CP^3 and more one-loop results from semiclassical strings
We evaluate the exact one-loop partition function for fundamental strings
whose world-surface ends on a cusp at the boundary of AdS_4 and has a "jump" in
CP^3. This allows us to extract the stringy prediction for the ABJM generalized
cusp anomalous dimension Gamma_{cusp}^{ABJM} (phi,theta) up to NLO in
sigma-model perturbation theory. With a similar analysis, we present the exact
partition functions for folded closed string solutions moving in the AdS_3
parts of AdS_4 x CP^3 and AdS_3 x S^3 x S^3 x S^1 backgrounds. Results are
obtained applying to the string solutions relevant for the AdS_4/CFT_3 and
AdS_3/CFT_2 correspondence the tools previously developed for their AdS_5 x S^5
counterparts.Comment: 48 pages, 2 figures, version 3, corrected misprints in formulas 2.12,
B.86, C.33, added comment on verification of the light-like limi
Spin Caloritronics
This is a brief overview of the state of the art of spin caloritronics, the
science and technology of controlling heat currents by the electron spin degree
of freedom (and vice versa).Comment: To be published in "Spin Current", edited by S. Maekawa, E. Saitoh,
S. Valenzuela and Y. Kimura, Oxford University Pres
Konishi operator at intermediate coupling
TBA equations for two-particle states from the sl(2) sector proposed by
Arutyunov, Suzuki and the author are solved numerically for the Konishi
operator descendent up to 't Hooft's coupling lambda ~ 2046. The data obtained
is used to analyze the properties of Y-functions and address the issue of the
existence of the critical values of the coupling. In addition we find a new
integral representation for the BES dressing phase which substantially reduces
the computational time.Comment: lots of figures, v2: improved numerics, c1=2, c2=0, c4 does not
vanis
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