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1.
We compute the boundary state associated with a moving Dp-brane in the presence of the open string tachyon field as a background field. The effect of the tachyon condensation on the
boundary state is discussed. It leads to a boundary state associated with a lower-dimensional moving D-brane or a stationary
instantonic D-brane. The former originates from condensation along the spatial directions and the latter comes from the temporal
direction of the D-brane worldvolume. Using the boundary state, we also study the interaction amplitude between two arbitrary
Dp
1- and Dp
2-branes. The long-range behavior of the amplitude is investigated, demonstrating an obvious deviation from the conventional
form, due to the presence of the background tachyon field. 相似文献
2.
In this article, we shall obtain the boundary state associated with a moving Dp-brane in the presence of the Kalb–Ramond field B μν , an internal U(1) gauge field A α and a tachyon field, in the compact spacetime. According to this state, properties of the brane and a closed string, with mixed boundary conditions emitted from it, will be obtained. Using this boundary state, we calculate the interaction amplitude of two moving Dp 1 and Dp 2-branes with above background fields in a partially compact spacetime. They are parallel or perpendicular to each other. Properties of the interaction amplitude will be analyzed, and contribution of the massless states to the interaction will be extracted. 相似文献
3.
In this article, we consider two m1-branes at angle in the presence of the background electric fields, in a partially compact spacetime. The branes have motions
along a common direction that is perpendicular to both of them. Using the boundary state formalism, we calculate their interaction
amplitude. Some special cases of this interaction will be studied in detail. 相似文献
4.
A spinor field interacting with a zero-mass neutral scalar field is considered for the case of the simplest type of direct
interaction, where the interaction Lagrangian has the formL
int
=1/2 ϕαϕ,α
F(S) whereF(S) is an arbitrary function of the spinor field invariantS=ψψ. Exact solutions of the corresponding systems of equations that take into account the natural gravitational field in a
plane-symmetric metric are obtained. It is proved that the initial system of equations has regular localized soliton-type
solutions only if the energy density of the zero-mass scalar field is negative as it “disengages” from interaction with the
spinor field. In two-dimensional space-time the system of field equations we are studying describes the configuration of fields
with constant energy densityT
00
, i.e., no soliton-like solutions exist in this case.
Russian People’s Friendship University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 69–75,
July, 1998. 相似文献
5.
6.
M. R. Setare 《International Journal of Theoretical Physics》2006,45(10):1799-1808
In this paper we study the Casimir effect for conformally coupled massless scalar fields on background of Static dS4+1 spacetime. We will consider the general plane–symmetric solutions of the gravitational field equations and boundary conditions of the Dirichlet type on the branes. Then we calculate the vacuum energy-momentum tensor in a configuration in which the boundary branes are moving by uniform proper acceleration in static de Sitter background. Static de Sitter space is conformally related to the Rindler space, as a result we can obtain vacuum expectation values of energy-momentum tensor for conformally invariant field in static de Sitter space from the corresponding Rindler counterpart by the conformal transformation. 相似文献
7.
Defining a spin connection is necessary for formulating Dirac's bispinor equation in a curved space-time. Hestenes has shown
that a bispinor field is equivalent to an orthonormal tetrad of vector fields together with a complex scalar field. In this
paper, we show that using Hestenes' tetrad for the spin connection in a Riemannian space-time leads to a Yang-Mills formulation
of the Dirac Lagrangian in which the bispinor field Ψ is mapped to a set of SL(2,R)× U(1) gauge potentials FαK and a complex scalar field ρ. This result was previously proved for a Minkowski space-time using Fierz identities. As an
application we derive several different non-Riemannian spin connections found in the literature directly from an arbitrary
linear connection acting on the tensor fields (FαK, ρ). We also derive spin connections for which Dirac's bispinor equation is form invariant. Previous work has not considered
form invariance of the Dirac equation as a criterion for defining a general spin connection. 相似文献
8.
We take a boundary-value approach to quantum amplitudes arising in gravitational collapse to a black hole. Pose boundary data
on initial and final space-like hypersurfaces Σ
F,I
, separated at spatial infinity by a Lorentzian proper-time interval T. Quantum amplitudes are calculated following Feynman's approach; rotate: T→|T|exp (−iθ) into the complex, where 0< θ≤π/2, and solve the corresponding well-posed complex classical boundary-value problem. We compute the classical Lorentzian action S
class and corresponding semi-classical quantum amplitude, proportional to exp (iS
class). To recover the Lorentzian amplitude, take the limit θ→ 0+ of the semi-classical amplitude. For the classical boundary-value problem with given perturbative boundary data, we compute
an effective spherically-symmetric energy-momentum tensor 〉 T
μν〈
EFF
, averaged over several wavelengths of the radiation, describing the averaged extra energy-momentum contribution in the Einstein
field equations, due to the perturbations. This takes the form of a null fluid, describing the radiation (of quantum origin)
streaming radially outwards. The classical space-time metric, in this region of the space time, is of Vaidya form, justifying
the adiabatic radial mode equations, for spins s = 0 and s = 2. 相似文献
9.
D. É. Fel’dman 《Journal of Experimental and Theoretical Physics》1999,88(6):1170-1178
The critical behavior of the transverse (with respect to the field) magnetization component in classical degenerate magnets
with only nearest-neighbors interaction in a uniaxial random magnetic field at zero temperature is found exactly. For a Gaussian
distribution of the random field the asymptotic transverse magnetization in strong fields does not depend on the dimension
of the space and is of the form m
⊥ ∝ 1nh
0/h
0
2
, where h
0 is the width of the distribution. For a bimodal distribution, where only the field direction is random and the amplitude
is fixed, the transverse magnetization behaves as m
⊥∝exp(−const/(H
c
−H)
D/2), where H is the amplitude of the random field, D is the dimension of the space, and H
c
is the critical field.
Zh. éksp. Teor. Fiz. 115, 2143–2159 (June 1999) 相似文献
10.
We investigate the deformation of D-brane world-volumes in curved backgrounds. We calculate the leading corrections to the boundary conformal field theory involving
the background fields, and in particular we study the correlation functions of the resulting system. This allows us to obtain
the world-volume deformation, identifying the open string metric and the noncommutative deformation parameter. The picture
that unfolds is the following: when the gauge invariant combination ω=B+F is constant one obtains the standard Moyal deformation of the brane world-volume. Similarly, when dω= 0 one obtains the noncommutative Kontsevich deformation, physically corresponding to a curved brane in a flat background.
When the background is curved, H=dω≠ 0, we find that the relevant algebraic structure is still based on the Kontsevich expansion, which now defines a nonassociative
star product with an A
∞ homotopy associative algebraic structure. We then recover, within this formalism, some known results of Matrix theory in
curved backgrounds. In particular, we show how the effective action obtained in this framework describes, as expected, the
dielectric effect of D-branes. The polarized branes are interpreted as a soliton, associated to the condensation of the brane gauge field.
Received: 22 March 2001 / Accepted: 13 July 2001 相似文献
11.
We explore the possibility that the dynamics of the universe can be reproduced choosing appropriately the initial global topology
of the Universe. In this work we start with two concentric spherical three-dimensional branes S
3, with radius a
1 < a
2 immersed in a five-dimensional space-time. The novel feature of this model is that in the interior brane there exist only
spin-zero fundamental fields (scalar fields), while in the exterior one there exist only spin-one fundamental interactions.
As usual, the bulk of the universe is dominated by gravitational interactions. In this model, like in the Ekpyrotic one, the
Big Bang is consequence of the collision of the branes and causes the existence of the particles predicted by the standard
model in the exterior brane (our universe). The scalar fields on the interior brane interact with the spin-one fields on the
exterior one only through gravitation, they induce the effect of Scalar Field Dark Matter with an ultra-light mass on the
exterior one. We discuss two different regimes where the energy density and the brane tension are compared, with the aim to
obtain the observed dynamics of the universe after the collision of the branes. 相似文献
12.
We derive effective actions for "spacelike branes" (S-branes) and find a solution describing the formation of fundamental strings in the rolling tachyon background. The S-brane action is a Dirac-Born-Infeld action for Euclidean world volumes defined in the context of time-dependent tachyon condensation of non-BPS (Bogomol'nyi-Prasad-Sommerfield) branes. It includes gauge fields and, in particular, a scalar field associated with translation along the time direction. We show that the BIon spike solutions constructed in this system correspond to the production of a confined electric flux tube (a fundamental string) at late time of the rolling tachyon. 相似文献
13.
14.
A. D. Balaev V. A. Gavrichkov S. G. Ovchinnikov V. K. Chernov T. G. Aminov G. G. Shabunina 《Journal of Experimental and Theoretical Physics》1998,86(5):1026-1029
In the magnetic field range ΔH=8–60 kOe we observed and studied the anomalous oscillations in the magnetic field dependence of the resistance and magnetization
of single crystals of n-HgCr2Se4. The absence of periodicity in 1/H in the ΔH=8–20 kOe range can be explained by the non-Fermi-liquid behavior of the electron subsystem and agrees with the theory of
the de Haas-van Alphen in systems with intermediate valence. In stronger fields, ΔH=20–60 kOe, the amplitude of the fundamental harmonic decreases, with the number and amplitude of the higher-order harmonics
increasing. As a result, noise is superimposed on the signal as magnetic field strength grows. The temperature dependence
of the magnetization is the sum of the monotonic spin-wave contribution and the oscillating part.
Zh. éksp. Teor. Fiz. 113, 1877–1882 (May 1998) 相似文献
15.
The generation of harmonics in a laser ablated YBCO film deposited on a 〈100〉 MgO substrate is reported. Higher odd harmonics
appeared when the film was subjected to an ac field. The presence of a dc field induces only the second harmonic with a small
value of slope ofV
2−H
dc curve (δV
2/δH
dc) compared to bulk YBCO. The variation of the amplitude of third harmonic (V
3) withH
ac and temperature was studied. These results are explained in terms of a critical state model. The observation of only a small
amplitude of second harmonic (V
2) with a smallδV
2/δH
dc is explained in terms of a special kind of clean grain boundary present in YBCO laser ablated films on 〈100〉 MgO. 相似文献
16.
M. N. Khlopkin 《JETP Letters》1999,69(1):26-30
The specific heat of a V3Si single crystal (T
c=17 K, H
c2=20 T) in magnetic fields up to 8 T isinvestigated experimentally for three orientations of the field relative to the crystallographic
directions — H∥〈001〉, H∥〈110〉, and H∥〈111〉. Both the upper critical magnetic field and the specific heat of the mixed state are observed to depend on the orientation
of the magnetic field relative to the crystallographic directions (anisotropy): The critical field reaches its maximum value
and the specific heat its minimum value in a field along the 〈001〉 direction. The anisotropy scale in both phenomena increases
as the magnetic field and reaches 3% in a 6 T field. The interrelationship of the upper critical field anisotropy and the
specific-heat anisotropy in type-II superconductors is studied. It is shown that the anisotropy of the specific heat in the
mixed state in weak fields can serve as a criterion for nontrivial pairing.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 1, 26–29 (10 January 1999) 相似文献
17.
Jacques Bros Henri Epstein Ugo Moschella 《Communications in Mathematical Physics》2002,231(3):481-528
We propose a general framework for studying quantum field theory on the anti-de-Sitter space-time, based on the assumption
of positivity of the spectrum of the possible energy operators. In this framework we show that the n-point functions are analytic in suitable domains of the complex AdS manifold, that it is possible to Wick rotate to the Euclidean
manifold and come back, and that it is meaningful to restrict AdS quantum fields to Poincaré branes. We give also a complete
characterization of two-point functions which are the simplest example of our theory. Finally we prove the existence of the
AdS-Unruh effect for uniformly accelerated observers on trajectories crossing the boundary of AdS at infinity, while that
effect does not exist for all the other uniformly accelerated trajectories.
Received: 3 December 2001 / Accepted: 26 July 2002 Published online: 21 October 2002 相似文献
18.
M. Malekjani A. Khodam-Mohammadi M. Taji 《International Journal of Theoretical Physics》2011,50(10):3112-3124
The polytropic gas model is investigated as an interacting dark energy scenario. The cosmological implications of the model
including the evolution of EoS parameter w
Λ, energy density ΩΛ and deceleration parameter q are investigated. We show that, depending on the parameter of model, the interacting polytropic gas can behave as a quintessence
or phantom dark energy. In this model, the phantom divide is crossed from below to up. The evolution of q in the context of polytropic gas dark energy model represents the decelerated phase at the early time and accelerated phase
later. The singularity of this model is also discussed. Eventually, we establish the correspondence between interacting polytropic
gas model with tachyon, K-essence and dilaton scalar fields. The potential and the dynamics of these scalar field models are
reconstructed according to the evolution of interacting polytropic gas. 相似文献
19.
A. V. Lazuta 《JETP Letters》1997,65(4):363-368
Recent results on the effect of magnetic field on the sound velocity V in aluminosilicate glasses doped with dysprosium are analyzed on the basis of a minimal model for the ground state of Dy3+ (Kramers ion with J=15/2) described by a wave function ϕ
± = ϕ
±
J
m + ηϕ
± 1/2. The first term represents a state with a large J projection on the local crystal field axis and the random parameter η(〈η〉=0, 〈η
2〉≪1) introduces a small admixture of the state ϕ
±1/2 into the ground state. The relative variation of V due to the resonance interaction of sound waves with this state split by H is determined as a function of H and T. It possesses a universal asymptotic behavior. Our results are in reasonable agreement with the experiment. A possible structure
of the crystal fields that can induce this state is discussed.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 4, 341–346 (25 February 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
20.
The motion of a tachyon in the empty Schwarzschild solution outside a massm is discussed. It is shown that a tachyon falling radially inwards never reaches the space-time singularity at the origin.
Instead, it is bounced back at a point inside the Schwarzschild radius. The causal and non-causal aspects of such a bounce
are considered. It is shown that a tachyon dropped from a radial co-ordinate <2.56m always airives before it went in whereas a tachyon dropped from a radial co-ordinate >3.27m always arrives later than its starting time. The more general case of a tachyon with a finite angular momentum is also analyzed.
The possible astrophysical consequences of the presence of tachyons near condensed or collapsing objects and black holes are
qualitatively discussed. 相似文献