2,490 research outputs found
Heavy Quarks on Anisotropic Lattices: The Charmonium Spectrum
We present results for the mass spectrum of mesons simulated on
anisotropic lattices where the temporal spacing is only half of the
spatial spacing . The lattice QCD action is the Wilson gauge action plus
the clover-improved Wilson fermion action. The two clover coefficients on an
anisotropic lattice are estimated using mean links in Landau gauge. The bare
velocity of light has been tuned to keep the anisotropic, heavy-quark
Wilson action relativistic. Local meson operators and three box sources are
used in obtaining clear statistics for the lowest lying and first excited
charmonium states of , , , and . The
continuum limit is discussed by extrapolating from quenched simulations at four
lattice spacings in the range 0.1 - 0.3 fm. Results are compared with the
observed values in nature and other lattice approaches. Finite volume effects
and dispersion relations are checked.Comment: 36 pages, 6 figur
TBA, NLO Luscher correction, and double wrapping in twisted AdS/CFT
The ground-state energy of integrably-twisted theories is analyzed in finite
volume. We derive the leading and next-to-leading order (NLO) L\"uscher-type
corrections for large volumes of the vacuum energy for integrable theories with
twisted boundary conditions and twisted S-matrix. We then derive the twisted
thermodynamic Bethe ansatz (TBA) equations to describe exactly the ground
state, from which we obtain an untwisted Y-system. The two approaches are
compared by expanding the TBA equations to NLO, and exact agreement is found.
We give explicit results for the O(4) model and for the three-parameter family
of -deformed (non-supersymmetric) planar AdS/CFT model, where the
ground-state energy can be nontrivial and can acquire finite-size corrections.
The NLO corrections, which correspond to double-wrapping diagrams, are
explicitly evaluated for the latter model at six loops.Comment: 42 pages, 2 figures, v2: references added, v3: minor correction
Spin- generalization of fractional exclusion statistics
We study fractional exclusion statistics for quantum systems with SU(2)
symmetry (arbitrary spin ), by generalizing the thermodynamic equations with
squeezed strings proposed by Ha and Haldane. The bare hole distributions as
well as the statistical interaction defined by an infinite-dimensional matrix
specify the universality class. It is shown that the system is described by the
level- WZW model and has a close relationship to non-abelian fractional
quantum Hall states. As a low-energy effective theory, the sector of {\it
massless} Z parafermions is extracted, whose statistical interaction is
given by a finite-dimensional matrix.Comment: 11pages, REVTE
Quantum finite-size effects for dyonic magnons in the AdS_4 x CP^3
We compute quantum corrections to finite-size effects for various dyonic
giant magnons in the AdS_4 x CP^3 in two different approaches. The off-shell
algebraic curve method is used to quantize the classical string configurations
in semi-classical way and to compute the corrections to the string energies.
These results are compared with the F-term L\"uscher formula based on the
S-matrix of the AdS_4 / CFT_3. The fact that the two results match exactly
provides another stringent test for the all-loop integrability conjecture and
the exact S-matrix based on it.Comment: 21 pages, No figures, corrected typos, added some reference
Solving the Simplest Theory of Quantum Gravity
We solve what is quite likely the simplest model of quantum gravity, the
worldsheet theory of an infinitely long, free bosonic string in Minkowski
space. Contrary to naive expectations, this theory is non-trivial. We
illustrate this by constructing its exact factorizable S-matrix. Despite its
simplicity, the theory exhibits many of the salient features expected from more
mature quantum gravity models, including the absence of local off-shell
observables, a minimal length, a maximum achievable (Hagedorn) temperature, as
well as (integrable relatives of) black holes. All these properties follow from
the exact S-matrix. We show that the complete finite volume spectrum can be
reconstructed analytically from this S-matrix with the help of the
thermodynamic Bethe Ansatz. We argue that considered as a UV complete
relativistic two-dimensional quantum field theory the model exhibits a new type
of renormalization group flow behavior, "asymptotic fragility". Asymptotically
fragile flows do not originate from a UV fixed point.Comment: 32+4 pages, 1 figure, v2: typos fixed, published versio
Glueball Properties at Finite Temperature in SU(3) Anisotropic Lattice QCD
The thermal properties of the glueballs are studied using SU(3) anisotropic
lattice QCD with beta=6.25, the renormalized anisotropy xi=a_s/a_t=4 over the
lattice of the size 20^3\times N_t with N_t = 24, 26, 28, 30, 33, 34, 35, 36,
37, 38, 40, 43, 45, 50, 72 at the quenched level. To construct a suitable
operator on the lattice, we adopt the smearing method, and consider its
physical meaning in terms of the operator size. First, we construct the
temporal correlators G(t) for the 0^{++} and 2^{++} glueballs, using more than
5,000 gauge configurations at each temperature. We then measure the pole-mass
of the thermal glueballs from G(t). For the lowest 0^{++} glueball, we observe
a significant pole-mass reduction of about 300 MeV near T_c or m_G(T\simeq T_c)
\simeq 0.8 m_G(T\sim 0), while its size remains almost unchanged as rho(T)
\simeq 0.4fm. Finally, for completeness, as an attempt to take into account the
effect of thermal width Gamma(T) at finite temperature, we perform a more
general new analysis of G(t) based on its spectral representation. By adopting
the Breit-Wigner form for the spectral function rho(omega), we perform the
best-fit analysis as a straightforward extension to the standard pole-mass
analysis. The result indicates a significant broadening of the peak as Gamma(T)
\sim 300 MeV as well as rather modest reduction of the peak center of about 100
MeV near T_c for the lowest 0^{++} glueball. The temporal correlators of the
color-singlet modes corresponding to these glueballs above T_c are also
investigated.Comment: This is the revised version using more gauge configurations near T_c.
25 pages, Latex2e, 22 figure
Scaling Laws and Effective Dimension in Lattice SU(2) Yang-Mills Theory with a Compactified Extra Dimension
Monte Carlo simulations are performed in a five-dimensional lattice SU(2)
Yang-Mills theory with a compactified extra dimension, and scaling laws are
studied. Our simulations indicate that as the compactification radius
decreases, the confining phase spreads more and more to the weak coupling
regime, and the effective dimension of the theory changes gradually from five
to four. Our simulations also indicate that the limit with
kept fixed exists both in the confining and deconfining phases if is
small enough, where is the lattice spacing in the four-dimensional
direction. We argue that the color degrees of freedom in QCD are confined only
for , where a rough estimate shows that lies
in the TeV range. Comments on deconstructing extra dimensions are given.Comment: 15 pages, TeX, 5 figure
Exact Conductance through Point Contacts in the Fractional Quantum Hall Effect
The conductance for tunneling through a point contact between two
quantum Hall edges is described by a universal scaling function, which has
recently been measured experimentally. We compute this universal function
exactly, by using the thermodynamic Bethe ansatz and a Boltzmann equation.Comment: 10 pages, 1 figur
The large longitudinal spread of solar energetic particles during the January 17, 2010 solar event
We investigate multi-spacecraft observations of the January 17, 2010 solar
energetic particle event. Energetic electrons and protons have been observed
over a remarkable large longitudinal range at the two STEREO spacecraft and
SOHO suggesting a longitudinal spread of nearly 360 degrees at 1AU. The flaring
active region, which was on the backside of the Sun as seen from Earth, was
separated by more than 100 degrees in longitude from the magnetic footpoints of
each of the three spacecraft. The event is characterized by strongly delayed
energetic particle onsets with respect to the flare and only small or no
anisotropies in the intensity measurements at all three locations. The presence
of a coronal shock is evidenced by the observation of a type II radio burst
from the Earth and STEREO B. In order to describe the observations in terms of
particle transport in the interplanetary medium, including perpendicular
diffusion, a 1D model describing the propagation along a magnetic field line
(model 1) (Dr\"oge, 2003) and the 3D propagation model (model 2) by (Dr\"oge et
al., 2010) including perpendicular diffusion in the interplanetary medium have
been applied, respectively. While both models are capable of reproducing the
observations, model 1 requires injection functions at the Sun of several hours.
Model 2, which includes lateral transport in the solar wind, reveals high
values for the ratio of perpendicular to parallel diffusion. Because we do not
find evidence for unusual long injection functions at the Sun we favor a
scenario with strong perpendicular transport in the interplanetary medium as
explanation for the observations.Comment: The final publication is available at http://www.springerlink.co
Ab Initio Calculation of Relativistic Corrections to the Static Interquark potential I: SU(2) Gauge Theory
We test the capability of state-of-the-art lattice techniques for a precise
determination of relativistic corrections to the static interquark potential,
by use of SU(2) gauge theory. Emphasis is put on the short range structure of
the spin dependent potentials, with lattice resolution a ranging from a approx
0.04 fm (at beta=2.74) down to a approx 0.02 fm (at beta=2.96) on volumes of
32^4 and 48^4 lattice sites. We find a new short range Coulomb-like
contribution to the spin-orbit potential V_1'.Comment: 37 pages REVTeX with 20 encapsuled ps figure
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