scholarly journals NEW REALIZATIONS OF W ALGEBRAS AND W STRINGS

1992 ◽  
Vol 07 (20) ◽  
pp. 1835-1842 ◽  
Author(s):  
H. LU ◽  
C.N. POPE ◽  
S. SCHRANS ◽  
X.J. WANG
Keyword(s):  
Energy Momentum Tensor ◽  
Scalar Fields ◽  
Momentum Tensor ◽  
Intrinsic Interest ◽  
New Class ◽  
Free Scalar ◽  
To Come ◽  
String Theories

We discuss new realizations of W algebras in which the currents are expressed in terms of two arbitrary commuting energy-momentum tensors together with a set of free scalar fields. This contrasts with the previously-known realizations, which involve only one energy-momentum tensor. Since realizations of nonlinear algebras are not easy to come by, the fact that this new class exists is of intrinsic interest. We use these new realizations to build the corresponding W-string theories and show that they are effectively described by two independent ordinary Virasoro-like strings.

scholarly journals QUANTIZING HIGHER-SPIN STRING THEORIES

1995 ◽  
Vol 10 (14) ◽  
pp. 2123-2142 ◽  
Author(s):  
H. LU ◽  
X.J. WANG ◽  
K.-W. XU ◽  
C.N. POPE ◽  
K. THIELEMANS
Keyword(s):  
String Theory ◽  
Classical Theory ◽  
Energy Momentum Tensor ◽  
Standard Form ◽  
Momentum Tensor ◽  
Minimal Models ◽  
Classical Level ◽  
Higher Spin ◽  
String Theories ◽  
The Way

In this paper, we examine the conditions under which a higher-spin string theory can be quantized. The quantizability is crucially dependent on the way in which the matter currents are realized at the classical level. In particular, we construct classical realizations for the W2,s algebra, which is generated by a primary spin-s current in addition to the energy-momentum tensor, and discuss the quantization for s≤8. From these examples we see that quantum BRST operators can exist even when there is no quantum generalization of the classical W2,s algebra. Moreover, we find that there can be several inequivalent ways of quantizing a given classical theory, leading to different BRST operators with inequivalent cohomologies. We discuss their relation to certain minimal models. We also consider the hierarchical embeddings of string theories proposed recently by Berkovits and Vafa, and show how the already known W strings provide examples of this phenomenon. Attempts to find higher-spin fermionic generalizations lead us to examine whether classical BRST operators for [Formula: see text](n odd) algebras can exist. We find that even though such fermionic algebras close up to null fields, one cannot build nilpotent BRST operators, at least of the standard form.

scholarly journals Energy-momentum tensor for scalar fields coupled to the dilaton in two dimensions

1999 ◽  
Vol 59 (6) ◽  
Author(s):  
Fernando C. Lombardo ◽  
Francisco D. Mazzitelli ◽  
Jorge G. Russo
Keyword(s):  
Energy Momentum Tensor ◽  
Scalar Fields ◽  
Momentum Tensor ◽  
Two Dimensions

scholarly journals PALATINI FORMULATION OF MODIFIED GRAVITY WITH A NON-MINIMAL CURVATURE-MATTER COUPLING

2011 ◽  
Vol 26 (20) ◽  
pp. 1467-1480 ◽  
Author(s):  
TIBERIU HARKO ◽  
TOMI S. KOIVISTO ◽  
FRANCISCO S. N. LOBO
Keyword(s):  
Energy Momentum Tensor ◽  
Equations Of Motion ◽  
Scalar Fields ◽  
Momentum Tensor ◽  
Nonlinear Dependence ◽  
Modified Theories Of Gravity ◽  
Field Equations ◽  
Test Particles ◽  
Theories Of Gravity ◽  
Minimal Curvature

We derive the field equations and the equations of motion for scalar fields and massive test particles in modified theories of gravity with an arbitrary coupling between geometry and matter by using the Palatini formalism. We show that the independent connection can be expressed as the Levi–Cività connection of an auxiliary, matter Lagrangian dependent metric, which is related with the physical metric by means of a conformal transformation. Similarly to the metric case, the field equations impose the nonconservation of the energy–momentum tensor. We derive the explicit form of the equations of motion for massive test particles in the case of a perfect fluid, and the expression of the extra-force is obtained in terms of the matter-geometry coupling functions and of their derivatives. Generally, the motion is non-geodesic, and the extra force is orthogonal to the four-velocity. It is pointed out here that the force is of a different nature than in the metric formalism. We also consider the implications of a nonlinear dependence of the action upon the matter Lagrangian.

Unified DE–DM with diffusive interactions scenario from scalar fields

2017 ◽  
Vol 26 (12) ◽  
pp. 1743021 ◽  
Author(s):  
David Benisty ◽  
E. I. Guendelman
Keyword(s):  
Dark Matter ◽  
Fixed Point ◽  
Energy Momentum Tensor ◽  
Scalar Fields ◽  
Equation Of Motion ◽  
Momentum Conservation ◽  
Momentum Tensor ◽  
Gravitational Energy ◽  
Spacetime Theory ◽  
Energy Momentum Conservation

Generalized models of unified dark matter (DM) and dark energy (DE) in the context of Two Measure Theories and of dynamical spacetime theories are obtained. In Two Measure Theories, one uses metric independent volume elements and this allows to construct unified DM and DE, where the cosmological constant appears as an integration constant associated to the equation of motion of the measure fields. The dynamical spacetime theories generalize the Two Measure Theories by introducing a vector field whose equation of motion guarantees the conservation of a certain energy–momentum tensor, which may be related, but in general is not the same as the gravitational energy–momentum tensor. By considering the dynamical space field appearing in another part of the action (apart from the coupling to the energy–momentum tensor), we can obtain noncovariant energy–momentum conservation. Then, the dynamical spacetime theory becomes a theory of diffusive unified DE and DM. The nonconserved energy–momentum tensors lead at the end to a formulation of interacting DE–DM models in the form of a diffusive type interacting unified DE and DM scenario. We solved analytically the theories for asymptotic solution, and we show that the [Formula: see text]CDM is a fixed point of these theories at large times.

scholarly journals QUANTUM EVOLUTION OF SCALAR FIELDS IN ROBERTSON-WALKER SPACE-TIME

1996 ◽  
Vol 11 (21) ◽  
pp. 3957-3971 ◽  
Author(s):  
H.C. REIS ◽  
O.J.P. ÉBOLI
Keyword(s):  
Field Theory ◽  
Energy Momentum Tensor ◽  
Gaussian Approximation ◽  
Scalar Fields ◽  
Momentum Tensor ◽  
Space Time ◽  
Quantum Evolution ◽  
Coupling Constant ◽  
Pure States ◽  
Schrödinger Picture

We study the λɸ4 field theory in a flat Robertson-Walker space-time using the functional Schrödinger picture. We introduce a simple Gaussian approximation to analyze the time evolution of pure states and we establish the renormalizability of the approximation. We also show that the energy–momentum tensor in this approximation is finite once we consider the usual mass and coupling constant renormalizations.

scholarly journals Warping wormholes with dust: a metric construction of the Python’s Lunch

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Ning Bao ◽  
Aidan Chatwin-Davies ◽  
Grant N. Remmen
Keyword(s):  
General Relativity ◽  
Mutual Information ◽  
Cosmological Constant ◽  
Cross Sections ◽  
Energy Momentum Tensor ◽  
Local Maximum ◽  
Momentum Tensor ◽  
Positive Energy ◽  
De Sitter ◽  
New Class

Abstract We show how wormholes in three spacetime dimensions can be customizably warped using pressureless matter. In particular, we exhibit a large new class of solutions in (2 + 1)-dimensional general relativity with energy-momentum tensor describing a negative cosmological constant and positive-energy dust. From this class of solutions, we construct wormhole geometries and study their geometric and holographic properties, including Ryu- Takayanagi surfaces, entanglement wedge cross sections, mutual information, and outer entropy. Finally, we construct a Python’s Lunch geometry: a wormhole in asymptotically anti-de Sitter space with a local maximum in size near its middle.

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