2,017 research outputs found
Asynchronous vibration problem of centrifugal compressor
An unstable asynchronous vibration problem in a high pressure centrifugal compressor and the remedial actions against it are described. Asynchronous vibration of the compressor took place when the discharge pressure (Pd) was increased, after the rotor was already at full speed. The typical spectral data of the shaft vibration indicate that as the pressure Pd increases, pre-unstable vibration appears and becomes larger, and large unstable asynchronous vibration occurs suddenly (Pd = 5.49MPa). A computer program was used which calculated the logarithmic decrement and the damped natural frequency of the rotor bearing systems. The analysis of the log-decrement is concluded to be effective in preventing unstable vibration in both the design stage and remedial actions
On the Generalised Pauli--Villars Regularization of the Standard Model
We show that the regularization of the Standard Model proposed by Frolov and
Slavnov describes a nonlocal theory with quite simple Lagrangian.Comment: 7 pages, harvma
A Perturbative Study of a General Class of Lattice Dirac Operators
A perturbative study of a general class of lattice Dirac operators is
reported, which is based on an algebraic realization of the Ginsparg-Wilson
relation in the form
where stands for a non-negative integer.
The choice corresponds to the commonly discussed Ginsparg-Wilson relation
and thus to the overlap operator. We study one-loop fermion contributions to
the self-energy of the gauge field, which are related to the fermion
contributions to the one-loop function and to the Weyl anomaly. We
first explicitly demonstrate that the Ward identity is satisfied by the
self-energy tensor. By performing careful analyses, we then obtain the correct
self-energy tensor free of infra-red divergences, as a general consideration of
the Weyl anomaly indicates. This demonstrates that our general operators give
correct chiral and Weyl anomalies. In general, however, the Wilsonian effective
action, which is supposed to be free of infra-red complications, is expected to
be essential in the analyses of our general class of Dirac operators for
dynamical gauge field.Comment: 30 pages. Some of the misprints were corrected. Phys. Rev. D (in
press
CP-violating theta parameter in the domain model of the QCD vacuum
A non-zero CP-violating parameter is treated in the domain model
which assumes a cluster-like vacuum structure whose units are characterised in
particular by a topological charge which is not necessarily an integer number.
In the present paper we restrict consideration to rational values of the
charge. The model has previously been shown to manifest confinement,
spontaneous chiral symmetry breaking and the absence of an axial U(1) Goldstone
boson. We find that the specific structure of the minima of the free energy
density of the domain ensemble forces a -periodicity of observables in
for any number of light quarks, that vacuum doubling occurs at
for any and any value of topological charge . These
features are in agreement with expectations based on anomalous Ward identities
and large effective theories. We find also additional values of
depending on for which vacuum doubling occurs.Comment: 10 pages, 6 figures. Final version with modification of Eq.(2),
additional references, minor typographical correction
Phase Operator for the Photon Field and an Index Theorem
An index relation is
satisfied by the creation and annihilation operators and of a
harmonic oscillator. A hermitian phase operator, which inevitably leads to
, cannot be consistently
defined. If one considers an dimensional truncated theory, a hermitian
phase operator of Pegg and Barnett which carries a vanishing index can be
defined. However, for arbitrarily large , we show that the vanishing index
of the hermitian phase operator of Pegg and Barnett causes a substantial
deviation from minimum uncertainty in a characteristically quantum domain with
small average photon numbers. We also mention an interesting analogy between
the present problem and the chiral anomaly in gauge theory which is related to
the Atiyah-Singer index theorem. It is suggested that the phase operator
problem related to the above analytic index may be regarded as a new class of
quantum anomaly. From an anomaly view point ,it is not surprising that the
phase operator of Susskind and Glogower, which carries a unit index, leads to
an anomalous identity and an anomalous commutator.Comment: 32 pages, Late
Fluctuation-dissipation theorem and quantum tunneling with dissipation
We suggest to take the fluctuation-dissipation theorem of Callen and Welton
as a basis to study quantum dissipative phenomena (such as macroscopic quantum
tunneling) in a manner analogous to the Nambu-Goldstone theorem for spontaneous
symmetry breakdown. It is shown that the essential physical contents of the
Caldeira-Leggett model such as the suppression of quantum coherence by Ohmic
dissipation are derived from general principles only, namely, the
fluctuation-dissipation theorem and unitarity and causality (i.e., dispersion
relations), without referring to an explicit form of the Lagrangian. An
interesting connection between quantum tunneling with Ohmic dissipation and the
Anderson's orthogonality theorem is also noted.Comment: To appear in Phys. Rev.
Remark on Pauli-Villars Lagrangian on the Lattice
It is interesting to superimpose the Pauli-Villars regularization on the
lattice regularization. We illustrate how this scheme works by evaluating the
axial anomaly in a simple lattice fermion model, the Pauli-Villars Lagrangian
with a gauge non-invariant Wilson term. The gauge non-invariance of the axial
anomaly, caused by the Wilson term, is remedied by a compensation among
Pauli-Villars regulators in the continuum limit. A subtlety in Frolov-Slavnov's
scheme for an odd number of chiral fermions in an anomaly free complex gauge
representation, which requires an infinite number of regulators, is briefly
mentioned.Comment: 14 pages, Phyzzx. The final version to appear in Phys. Rev.
Bosonization in d=2 from finite chiral determinants with a Gauss decomposition
We show how to bosonize two-dimensional non-abelian models using finite
chiral determinants calculated from a Gauss decomposition. The calculation is
quite straightforward and hardly more involved than for the abelian case. In
particular, the counterterm , which is normally motivated from gauge
invariance and then added by hand, appears naturally in this approach.Comment: 4 pages, Revte
Topological properties of Berry's phase
By using a second quantized formulation of level crossing, which does not
assume adiabatic approximation, a convenient formula for geometric terms
including off-diagonal terms is derived. The analysis of geometric phases is
reduced to a simple diagonalization of the Hamiltonian in the present
formulation. If one diagonalizes the geometric terms in the infinitesimal
neighborhood of level crossing, the geometric phases become trivial for any
finite time interval . The topological interpretation of Berry's phase such
as the topological proof of phase-change rule thus fails in the practical
Born-Oppenheimer approximation, where a large but finite ratio of two time
scales is involved.Comment: 9 pages. A new reference was added, and the abstract and the
presentation in the body of the paper have been expanded and made more
precis
Invariant Regularization of Anomaly-Free Chiral Theories
We present a generalization of the Frolov-Slavnov invariant regularization
scheme for chiral fermion theories in curved spacetimes. local gauge symmetries
of the theory, including local Lorentz invariance. The perturbative scheme
works for arbitrary representations which satisfy the chiral gauge anomaly and
the mixed Lorentz-gauge anomaly cancellation conditions. Anomalous theories on
the other hand manifest themselves by having divergent fermion loops which
remain unregularized by the scheme. Since the invariant scheme is promoted to
also include local Lorentz invariance, spectator fields which do not couple to
gravity cannot be, and are not, introduced. Furthermore, the scheme is truly
chiral (Weyl) in that all fields, including the regulators, are left-handed;
and only the left-handed spin connection is needed. The scheme is, therefore,
well suited for the study of the interaction of matter with all four known
forces in a completely chiral fashion. In contrast with the vectorlike
formulation, the degeneracy between the Adler-Bell-Jackiw current and the
fermion number current in the bare action is preserved by the chiral
regularization scheme.Comment: 28pgs, LaTeX. Typos corrected. Further remarks on singlet current
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