arXiv subjects

J. X. Lu

Publications and source records attributed to J. X. Lu.

70 records · Page 4Linked to original sources

arXiv1999

(F, D5) Bound State, SL(2, Z) Invariance and The Descendant States in Type IIB/A String Theory

Recently the space-time configurations of a set of non-threshold bound states, called the (F, Dp) bound states, have been constructed explicitly for every $p$ with $2 \le p \le 7$ in both type IIA (for $p$ even) and type IIB (for $p$ odd) string theories by the present authors. By making use of the SL(2, Z) symmetry of type IIB theory we construct a more general SL(2, Z) invariant bound state of the type ((F, D1), (NS5, D5)) in this theory from the (F, D5) bound state. There are actually an infinite number of $(m,n)$ strings forming bound states with $(m',n')$ 5-branes, where strings lie along one of the spatial directions of the 5-branes. By applying T-duality along one of the transverse directions we also construct the bound state ((F, D2), (KK, D6)) in type IIA string theory. Then we give a list of possible bound states which can be obtained from these newly constructed bound states by applying T-dualities along the longitudinal directions as well as S-dualities to those in type IIB theory.

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arXiv1999

((F, D1), D3) Bound State and Its T-dual Daughters

In the previous paper [hep-th/9904129], we constructed a general explicit BPS solution for (F, D3) non-threshold bound state. By using the SL(2,Z) symmetry of type IIB string theory, we here construct from (F, D3) a more general BPS configuration for a D3 brane with certain units of quantized 5-form flux and an infinite number of parallel (F, D1)-strings. We study its decoupling limit and find that given Maldacena's $AdS_5/CFT_4$ correspondence with respect to simple D3 branes and with the usual string coupling, we should have a similar correspondence with respect to this bound state but now with an effective string coupling. We discuss possible descendants of this bound state by T-dualities along its longitudinal or transverse directions. In particular, we present explicit configurations for ((F, Dp), D(p + 2)) bound states for $2 \le p \le 5$. All these configurations preserve one half of the spacetime supersymmetries.

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arXiv1999

Non-threshold (F, Dp) bound states

In the previous paper [hep-th/9904112], we argued that there exist BPS bound states of Dp branes carrying certain units of quantized constant electric field for every $p$ (with $1 \le p \le 8$). Each of these bound states preserves one half of the spacetime supersymmetries. In this paper, we construct these bound state configurations explicitly for $2 \le p \le 7$ from Schwarz's $(m,n)$-string or (F, D1) bound state in type IIB string theory by T-dualities along the transverse directions. We calculate the charge per $(2π)^{p -1} α'^{(p - 1)/2}$ of $(p -1)$-dimensional area for F-strings in (F, Dp) and the tension for each of these bound states. The results agree precisely with those obtained previously from the worldvolume study. We study the decoupling limit for the (F, D3) bound state and find that Maldacena's $AdS_5/CFT_4$ correspondence may hold true even with respect to thisbound state but now with an effective string coupling rather than the usual string coupling. This coupling is quantized and can be independent of the usual string coupling in certain limit.

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arXiv1999

(m,n)-String-Like Dp-Brane Bound States

An (m, n)-string bound state (with m, n relatively prime integers) in type IIB string theory can be interpreted from the D-string worldsheet point of view as n D-strings carrying m units of quantized electric flux or quantized electric field. We argue, from the D-brane worldvolume point of view, that similar Dp-brane bound states should also exist for $2 \le p \le 8$ in both type IIA (when $p$ is even) and type IIB (when $p$ is odd) string theories. As in $p = 1$ case, these bound states can each be interpreted as $n$ Dp-branes carrying m units of quantized constant electric field. In particular, they all preserve one half of the spacetime supersymmetries.

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arXiv1999

Embedding AdS Black Holes in Ten and Eleven Dimensions

We construct the non-linear Kaluza-Klein ansätze describing the embeddings of the U(1)^3, U(1)^4 and U(1)^2 truncations of D=5, D=4 and D=7 gauged supergravities into the type IIB string and M-theory. These enable one to oxidise any associated lower dimensional solutions to D=10 or D=11. In particular, we use these general ansätze to embed the charged AdS_5, AdS_4 and AdS_7 black hole solutions in ten and eleven dimensions. The charges for the black holes with toroidal horizons may be interpreted as the angular momenta of D3-branes, M2-branes and M5-branes spinning in the tranverse dimensions, in their near-horizon decoupling limits. The horizons of the black holes coincide with the worldvolumes of the branes. The Kaluza-Klein ansätze also allow the black holes with spherical or hyperbolic horizons to be reinterpreted in D=10 or D=11.

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arXiv1998

4-string Junction and Its Network

We study a BPS configuration in which four strings (of different type) meet at a point in $N = 2, D = 8$ supergravity, i.e., the low energy effective theory of $T^2$-compactified type II string theory. We demonstrate that the charge conservation of the four strings implies the vanishing of the net force (due to the tensions of various strings) at the junction and vice versa, using the tension formula for $SL(3, Z)$ strings obtained recently by the present authors. We then show that a general 4-string junction preserves 1/8 of the spacetime supersymmetries. Using 4-string junctions as building blocks, we construct a string network which also preserves 1/8 of the spacetime supersymmetries.

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arXiv1998

U-duality p-Branes in Diverse Dimensions

U-duality p-branes in toroidally compactified type II superstring theories in space-time dimensions $10 > D \ge 4$ can be constructed explicitly based on the conjectured U-duality symmetries and the corresponding known single-charge super p-brane configurations. As concrete examples, we first construct explicitly the $SL(3, Z)$ superstrings and $SL(3, Z) \times SL(2, Z)$ 0-branes as well as their corresponding magnetic duals in $D = 8$. For the $SL(3, Z)$ superstrings (3-branes), each of them is characterized by a triplet of integers corresponding to the electric-like (magnetic-like) charges associated with the three 2-form gauge potentials present in the theory. For the $SL(3, Z)\times SL(2,Z)$ 0-branes (4-branes), each of them is labelled by a pair of triplets of integers corresponding to the electric-like (magnetic-like) charges associated with the two sets of three 1-form gauge potentials. The string (3-brane) tension and central charge are shown to be given by $SL(3, Z)$ invariant expressions. It is argued that when any two of the three integers in the integral triplet are relatively prime to each other, the corresponding string (3-brane) is stable and does not decay into multiple strings (3-branes) by a `tension gap' or `charge gap' equation. Similar results hold also for the 0-branes (4-branes). Alongwith the $SL(2, Z)$ dyonic membranes of Izquierdo et. al., these examples provide a further support for the conjectured $SL(3, Z) \times SL(2, Z)$ U-duality symmetry in this theory. Moreover, the study of these examples along with the previous ones provides us a recipe for constructing the U-duality p-branes of various supergravity theories in diverse dimensions. Constructions for these U-duality p-branes are also given.

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arXiv1998

An SL(2, Z) Multiplet of Type IIB Super Five-Branes

It is well-known that the low energy string theory admits a non-singular solitonic super five-brane solution which is the magnetic dual to the fundamental string solution. By using the symmetry of the type IIB string theory, we construct an SL(2, Z) multiplet of magnetically charged super five-branes starting from this solitonic solution. These solutions are characterized by two integral three-form charges $(q_1, q_2)$ and are stable when the integers are coprime. We obtain an expression for the tension of these $(q_1, q_2)$ five-branes as envisaged by Witten. The SL(2, Z) multiplets of black strings and black fivebranes and the existence of similar magnetic dual solutions of strings in type II string theory in $D < 10$ have also been discussed.

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arXiv1997

Remarks on M-theory coupling constants and M-brane tension quantizations

In the absence of a complete M-theory, we gather certain quantum aspects of this theory, namely, M-2 and M-5 brane duality and their tension quantization rule $2κ^2 T_2 T_5 = 2 πn$, the M-2 brane tension quantization $T_2 =\bigg({(2π)^2/2κ^2 m}\bigg)^{1/3}$, supersymmetry, perturbative gauge and gravitational anomaly cancellations, and the half-integral quantization of [$G^W/2π$], and study the consistency among these quantum effects. We find: (1) The complete determination of Hourava-Witten's $η= λ^6 /κ^4$ for M-theory on $R^{10} \times S^1/ Z_2$ requires not only the cancellation of M-theory gauge anomaly but also that of the gravitational anomaly, the quantization of M-2 brane tension, and the recently recognized half-integral quantization of $[G^W / 2 π]$. (2) A well-defined quantum M-theory necessarily requires the presence of both M-2 and M-5 branes and allows only $n = 1$ and $m =1$ for the respectively quantized M-2 and M-5 brane tensions. Implications of the above along with other related issues are discussed.

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arXiv1997

The Octonionic Membrane

We generalize the supermembrane solution of D=11 supergravity by permitting the 4-form $G$ to be either self-dual or anti-self-dual in the eight dimensions transverse to the membrane. After analyzing the supergravity field equations directly, and also discussing necessary conditions for unbroken supersymmetry, we focus on two specific, related solutions. The self-dual solution is not asymptotically flat. The anti-self-dual solution is asymptotically flat, has finite mass per unit area and saturates the same mass=charge Bogomolnyi bound as the usual supermembrane. Nevertheless, neither solution preserves any supersymmetry. Both solutions involve the octonionic structure constants but, perhaps surprisingly, they are unrelated to the octonionic instanton 2-form $F$, for which $TrF \wedge F$ is neither self-dual nor anti-self-dual.

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arXiv1994

String Solitons

We review the status of solitons in superstring theory, with a view to understanding the strong coupling regime. These {\it solitonic} solutions are non-singular field configurations which solve the empty-space low-energy field equations (generalized, whenever possible, to all orders in $α'$), carry a non-vanishing topological "magnetic" charge and are stabilized by a topological conservation law. They are compared and contrasted with the {\it elementary} solutions which are singular solutions of the field equations with a $σ$-model source term and carry a non-vanishing Noether "electric" charge. In both cases, the solutions of most interest are those which preserve half the spacetime supersymmetries and saturate a Bogomol'nyi bound. They typically arise as the extreme mass=charge limit of more general two-parameter solutions with event horizons. We also describe the theory {\it dual} to the fundamental string for which the roles of elementary and soliton solutions are interchanged. In ten spacetime dimensions, this dual theory is a superfivebrane and this gives rise to a string/fivebrane duality conjecture according to which the fivebrane may be regarded as fundamental in its own right, with the strongly coupled string corresponding to the weakly coupled fivebrane and vice-versa. After compactification to four spacetime dimensions, the fivebrane appears as a magnetic monopole or a dual string according as it wraps around five or four of the compactified dimensions. This gives rise to a four-dimensional string/string duality conjecture which subsumes a Montonen-Olive type duality in that the magnetic monopoles of the fundamental string correspond to the electric winding states of the dual string. This leads to a {\it duality of dualities} whereby under string/string duality the the strong/weak coupling $S$-duality trades places with the minimum/maximum length $T$-duality. Since these magnetic monopoles are extreme black holes, a prediction of $S$-duality is that the corresponding electric massive states of the fundamental string are also extreme black holes.

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arXiv1993

Black and super p-branes in diverse dimensions

We present a generic Lagrangian, in arbitrary spacetime dimension $D$, describing the interaction of a dilaton, a graviton and an antisymmetric tensor of arbitrary rank $d$. For each $D$~and~$d$, we find ``solitonic'' black $\tilde{p}$-brane solutions where $\tilde{p} = \tilde{d} - 1$~and~ $\tilde d = D - d - 2$. These solutions display a spacetime singularity surrounded by an event horizon, and are characterized by a mass per unit $\tilde p$-volume, ${\cal M}_{\tilde{d}}$, and topological ``magnetic'' charge $g_{\tilde{d}}$, obeying $κ{\cal M}_{\tilde{d}} \geq g_{\tilde{d}}/ \sqrt{2}$. In the extreme limit $κ{\cal M}_{\tilde{d}}=g_{\tilde{d}}/ \sqrt{2}$, the singularity and event horizon coalesce. For specific values of $D$~and~$d$, these extreme solutions also exhibit supersymmetry and may be identified with previously classified heterotic, Type IIA and Type IIB super $\tilde p$-branes. The theory also admits elementary $p$-brane solutions with ``electric'' Noether charge $e_d$, obeying the Dirac quantization rule $e_d g_{\tilde{d}} = 2πn$, $n =$~integer. We also present the Lagrangian describing the theory dual to the original theory, whose antisymmetric tensor has rank $\tilde{d}$ and for which the roles of topological and elementary solutions are interchanged. The super $p$-branes and their duals are mutually non-singular. As special cases of our general solution we recover the black $p$-branes of Horowitz and Strominger $(D = 10)$, Guven $(D = 11)$ and Gibbons et al $(D = 4)$, the $N = 1$, $N = 2a$~and~$N = 2b$ super-$p$-branes of Dabholkar et al $(4 \leq D \leq 10)$, Duff and Stelle $(D = 11)$, Duff and Lu $(D = 10)$ and Callan, Harvey and Strominger $(D = 10)$, and the axionic instanton of Rey $(D = 4)$. In particular, the electric/magnetic duality of Gibbons and Perry in $D = 4$ is seen to be a consequence of particle/sixbrane duality in $D = 10$. Among the new solutions is a self-dual superstring in $D = 6$.

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arXiv1993

ADM masses for black strings and p-branes

An ADM mass formula is derived for a wide class of black solutions with certain spherical symmetry. By applying this formula, we calculate the ADM masses for recently discovered black strings and $p$-branes in diverse dimensions. By this, the Bogolmol'nyi equation can be shown to hold explicitly. A useful observation is made for non-extremal black $p$-branes that only for $p = 0$, i.e. for a black hole, can its ADM mass be read directly from the asymptotic behaviour of the metric component $g_{00}$.

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arXiv1993

On the determination of the dilaton-antisymmetric tensor couplings in supergravity theories

A new approach is provided to determine the dilaton--antisymmetric tensor coupling in a supergravity theory by considering the static supersymmetric field configuration around a super extended object, which is consistently formulated in a curved superspace. By this, the corresponding SUSY transformation rules can also be determined for vanishing fermionic fields as well as bosonic fields other than those in the determined coupling. Therefore, we can, in turn, use this determined part of the supergravity theory to study all the related vacuum-like solutions. We have determined the dilaton--antisymmetric tensor couplings, in which each of the antisymmetric tensors is a singlet of the automorphism group of the corresponding superalgebra, for every supergravity multiplet. This actually happens only for $N \leq 2$ supergravity theories, which agrees completely with the spin-content analysis and the classified $N \leq 2$ super $p$-branes, therefore giving more support to the existence of the fundamental Type II $p$-branes. A prediction is made of the $D = 9, N = 2$ supergravity which has not yet been written down so far.

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arXiv1992

Type II p-branes: the brane-scan revisited

We re-examine the classification of supersymmetric extended objects in the light of the recently discovered Type II p-branes, previously thought not to exist for p> 1. We find new points on the brane-scan only in D = 10 and then only for p = 3(Type IIB), p = 4 (Type IIA), p = 5 (Type IIA and IIB) and p = 6 (Type IIA). The case D = 10, p = 2 (Type IIA) also exists but is equivalent to the previously classified D = 11 supermembrane.

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arXiv1991

String and Fivebrane Solitons: Singular or Non-singular?

We ask whether the recently discovered superstring and superfivebrane solutions of D=10 supergravity admit the interpretation of non-singular solitons even though, in the absence of Yang-Mills fields, they exhibit curvature singularities at the origin. We answer the question using a test probe/source approach, and find that the nature of the singularity is probe-dependent. If the test probe and source are both superstrings or both superfivebranes, one falls into the other in a finite proper time and the singularity is real, whereas if one is a superstring and the other a superfivebrane it takes an infinite proper time (the force is repulsive!) and the singularity is harmless. Black strings and fivebranes, on the other hand, always display real singularities.

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