REVIEW
BPS Bound States Of D0-D6 And D0-D8 Systems In A B-Field
High Energy Physics - Theory · Submitted 7 Dec 2000 · 32 references
Pith's verdict: A clean, short paper that gets a real conceptual point — BPS state counts can jump across a codimension-one locus — with one link (R^10 to T^6) asserted rather than argued.
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Referee report
The paper
The paper claims
A magnetic field can switch a BPS bound state on or off
The reading
What carries the argument
The load-bearing device is the identification of $r = v_1+v_2+v_3-1/2$ with the Fayet-Iliopoulos parameter of the D0-brane quantum mechanics, so that the D-term potential $V sim (|varphi|^2-r)^2$ converts a worldsheet ground-state energy computation into a statement about which side of the supersymmetric locus supports a Higgsed, massive, supersymmetric vacuum. The worldsheet side of the argument is the reflection matrix: a string ending on the D6-brane in a $B$-field is rotated by an $SO(6)$ element $M$ built from the three angles $v_i$, and unbroken supersymmetry requires $rho(-M)epsilon = epsilon$, i.e. that $-M$ lie in an $SU(3)$ subgroup, which is exactly $v_1+v_2+v_3=1/2$. The two computations meet because the same angles fix both the spinor projection and the Neveu-Schwarz zero-point energy.
Extended reading notes
Core claim
The paper establishes that the D0-D6 system in a constant $B$-field has a supersymmetric locus of real codimension one, $v_1+v_2+v_3=1/2$, where the $v_i$ are the three rotation angles conjugate to the $B$-field blocks and are related to it by $e^{2i v_i}=(1+ib_i)/(1-ib_i)$. On this locus the 0-6 and 6-0 strings contribute a single massless chiral multiplet, and the low-energy quantum mechanics is a $0+1$ dimensional $U(1)$ gauge theory with four supercharges, a chiral multiplet $Phi$, and a Fayet-Iliopoulos parameter $r=v_1+v_2+v_3-1/2$ entering the potential as $V sim (|varphi|^2-r)^2$. For $r<0$ the vacuum sits at $varphi=0$ with supersymmetry spontaneously broken and a Coulomb branch along which the branes separate; for $r>0$ the stable vacuum has $|varphi|=sqrt{r}$, the gauge symmetry is Higgsed, every component of the vector and chiral multiplets is massive, and the object is a D0-D6 bound state. The index $mathrm{Tr}(-1)^F$ therefore reads $0$ on one side and $1$ on the other, which is possible only because at $r=0$ the continuous spectrum above the $varphi=0$ vacuum begins at zero energy and the counting of zero-energy states degenerates. Compactified on $T^6$ with the D6 wrapped, the $r>0$ vacuum is a finite-energy $1/8$ BPS state, so the number of such states jumps as the moduli are changed. The paper then repeats the analysis for D0-D8, where a second supersymmetric locus $sum_i v_i = 1$ (with all $v_i$ positive, $0 le v_i < 1/2$) is not continuously connected to the familiar $B=0$ D0-D8 system, and where the Neveu-Schwarz ground state energy $(1/2)(1-sum_i v_i)$ again changes sign, giving a bound state for $sum_i v_i > 1$. Finally, taking $b_i to pminfty$ while preserving supersymmetry, the condition becomes $pm 1/b_1 pm 1/b_2 pm 1/b_3 = 0$, which is reproduced independently in noncommutative Yang-Mills theory from the gluino variation $delta lambda = hat{Gamma}^{ij}hat{F}_{ij}epsilon + epsilon'$ evaluated on the rank-one soliton with $hat{F}_{ij} = -Pi, theta^{-1}_{ij}$.
Load-bearing premise
The bound-state claim depends on reading the D0-D6 quantum mechanics as a $U(1)$ gauge theory whose Fayet-Iliopoulos parameter is $r=v_1+v_2+v_3-1/2$, an identification made by analogy with the D0-D4 system rather than derived from the worldsheet, and on the classical $r>0$ Higgs vacuum surviving quantum corrections.
Editorial extensions
If this is right
- In Type IIA string theory on $T^6$, the count of $1/8$ BPS states is not a topological invariant of the vacuum: it changes as the $B$-field moduli cross the locus $v_1+v_2+v_3=1/2$.
- The D0-D6 bound state exists only when the Fayet-Iliopoulos parameter is positive, so unlike D0-D4 instantons it has no zero-$B$ analogue and its size is bounded by the trace of the D-term equation.
- For $N$ D0-branes and $M$ D6-branes the classical moduli space of bound states is the space of $N$-plets of orthonormal vectors in $mathbb{C}^M$ modulo $U(N)$, i.e. a Grassmannian $U(M)/(U(N) times U(M-N))$ when the transverse scalars vanish, which requires $M ge N$.
- The D0-D8 system has a second supersymmetric locus, not connected to the $B=0$ one, and on that locus it develops a bound state when $sum_i v_i > 1$.
- In the large-$B$ limit the supersymmetric D0-D6 and D0-D8 configurations and their bound states admit a noncommutative Yang-Mills description, so the decay to the bound state could in principle be followed there.
Reading between the lines
- If the count of $1/8$ BPS states can jump under a smooth change of moduli with all 32 supercharges unbroken, then any microscopic counting of four-dimensional BPS black hole states that assumes moduli-independence across such a locus needs to be checked against this example.
- The mechanism is local: a continuous spectrum whose threshold touches zero at the locus. The same pattern should produce jumps wherever a would-be BPS state sits at the edge of a continuum, which suggests looking for analogous degenerations in other D$p$-D$p' systems with a codimension-one supersymmetric locus.
- The paper's index argument is a semi-classical one, resting on the $r>0$ vacuum being isolated and massive. A direct worldsheet or matrix-model computation of the $r>0$ ground state, rather than an argument from the absence of a Goldstone fermion, would be the natural next check.
Original abstract
The D0-D6 system, which is not supersymmetric in the absence of a Neveu-Schwarz B-field, becomes supersymmetric if a suitable constant B-field is turned on. On one side of the supersymmetric locus, this system has a BPS bound state, and on the other side it does not. After compactification on T^6, this gives a simple example in which the number of 1/8 BPS states jumps as the moduli of the compactification are changed. The D0-D8 system in a B-field has two different supersymmetric loci, only one of which is continuously connected to the familiar supersymmetric D0-D8 system without a B-field. In a certain range, the D0-D8 system also has a BPS bound state. In the limit in which the B-field goes to infinity, supersymmetric D0-D6 and D0-D8 systems and their bound states can be studied using noncommutative Yang-Mills theory.
The compiled record
The paper's own sentences, arranged, kept beside the review and separate from it. Each label is drawn from a closed vocabulary; the number beside it is the probability the classifier gave that label. Numbers in the tables are the authors', checked by code. No sentence in this record was written by a model.
The abstract, sentence by sentence
The D0-D6 system, which is not supersymmetric in the absence of a Neveu-Schwarz B-field, becomes supersymmetric if a suitable constant B-field is turned on. On one side of the supersymmetric locus, this system has a BPS bound state, and on the other side it does not. After compactification on T^6, this gives a simple example in which the number of 1/8 BPS states jumps as the moduli of the compactification are changed. The D0-D8 system in a B-field has two different supersymmetric loci, only one of which is continuously connected to the familiar supersymmetric D0-D8 system without a B-field. In a certain range, the D0-D8 system also has a BPS bound state. In the limit in which the B-field goes to infinity, supersymmetric D0-D6 and D0-D8 systems and their bound states can be studied using noncommutative Yang-Mills theory.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | The D0-D6 system, which is not supersymmetric in the absence of a Neveu-Schwarz B-field, becomes supersymmetric if a suitable constant B-field is turned on. | result 0.75 | 0.44 | 0.20 | asserted 1.00 |
| s1 | On one side of the supersymmetric locus, this system has a BPS bound state, and on the other side it does not. | result 1.00 | 0.68 | 0.21 | asserted 1.00 |
| s2 | After compactification on T^6, this gives a simple example in which the number of 1/8 BPS states jumps as the moduli of the compactification are changed. | interpretation 0.54 | 0.73 | 0.31 | asserted 1.00 |
| s3 | The D0-D8 system in a B-field has two different supersymmetric loci, only one of which is continuously connected to the familiar supersymmetric D0-D8 system without a B-field. | result 0.97 | 0.75 | 0.13 | asserted 1.00 |
| s4 | In a certain range, the D0-D8 system also has a BPS bound state. | result 1.00 | 0.76 | 0.12 | asserted 1.00 |
| s5 | In the limit in which the B-field goes to infinity, supersymmetric D0-D6 and D0-D8 systems and their bound states can be studied using noncommutative Yang-Mills theory. | method 0.70 | 0.41 | 0.16 | asserted 0.75 |
What was examined, and what was not
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References
How the literature uses it
36 arXiv papers cite this in 58 sentences
Papers citing it · 42 sentences without a confident label
Builds on it 2 papers
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Adding the background D6 brane extends this quiver by a new $U(1)$ node, with a single field, $q$, coming from the 0-6 strings, transforming in the bifundamental, as shown in [ref] .
Topological Quiver Matrix Models and Quantum Foam · Introduction · 0.88
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Some of the future directions in which this work could be continued are listed in the following. * According to [ref] , a supersymmetric bound state can be formed by the D$1$-D$9$ system if we turn on a constant $B$-field satisfying [equation] Therefore, we can generalize the tetrahedron instantons by adding a stack of D$9$-branes without further breaking the supersymmetry if the $B$-field satisfies the condition [equation] This generalization can also be viewed as instantons in the magnificent four model with all possible real codimension-two defects.
Tetrahedron instantons · Conclusions and future directions · 0.83
Uses its method or tool 2 papers
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We will follow [ref] to account for the B-field background– recall we have turned B-field on $TN_1$[Note that the D6-branes at angles configuration is equivalent to D0-D6 brane system with B-field on ND directions [ref] .].
Evidence for an Algebra of $\boldsymbol{G_2}$ Instantons · String quantization · 0.94
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In general, this choice of flux will break supersymmetry on the D8-brane, though the D0-brane may still experience an effective supersymmetric quantum mechanics.[Following [ref] , to study the unbroken supersymmetries in the presence of this flux, introduce the block diagonal matrix $M$ in the $8_v$ representation (see e.g. [ref] ): M=i=14⊕M_i, M_i=[ [ cos2πv_i sin2πv_i; -sin2πv_i cos2πv_i ] ] . where each $v_j$ is given by: exp2πiv_j=1+if_j/1-if_j.
Instantons, Twistors, and Emergent Gravity · Brane Construction · 0.88
Compares with it 2 papers
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The critical value of the field [ref] also agrees with the value computed in perturbative string theory [ref] .
Black Rings in Taub-NUT and D0-D6 interactions · Extremal ring with $B≠0$ · 0.93
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This is reminiscent of the same phenomenon discussed in [ref] .
D1-D3 (or $\bar{\textrm{D}3}$) Systems with Fluxes · Conclusions and Discussions · 0.98
Cites it as support 3 papers
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In other words, instanton solutions on $^6$ or $^8$ only exist for $ξ>0$: there are no stable BPS bound states of D$0$–D$(2n)$-branes in $2n$ dimensions for $n=3,4$ unless a (supersymmetry preserving) Kalb-Ramond field is turned on [ref] .
Noncommutative Instantons in Diverse Dimensions · ADHM Quiver Matrix Model · 0.99
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The reason why we should impose the constraint [ref] might be related to the fact that $D6$-$D0$ system cannot make a BPS bound state without an appropriate flux along the $D6$ branes [ref] .
Quiver Matrix Model and Topological Partition Function in Six Dimensions · Introduction · 0.98
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Thus the interesting case for us is $ζ>0$; in this case the D1–D9-brane system is tachyonic and unstable [ref] , so it decays to a supersymmetric vacuum via tachyon condensation.
Instanton Counting and Donaldson-Thomas Theory on Toric Calabi-Yau Four-Orbifolds · Physical Interpretation · 0.97
Cites it as background 7 papers
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D0 – D8 bound states were considered in [ref] as UV descriptions of $𝒩=(8,0)$ superconformal quantum mechanics.
$\textrm{AdS}_{2}\times S^7$ solutions from D0 $-$ F1 $-$ D8 intersections · AdS$_2$ solutions from D0 – F1 – D8 intersections · 0.83
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The problem of adhering $D0$-branes to $D6$-branes in a supersymmetric manner was first considered by Witten [ref] [See also related work in [ref] .].
Constituent Model of Extremal non-BPS Black Holes · Multi-center BPS solutions and decay of the non-BPS $D0-D6$ black holes · 0.97
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We also turn on a background B-field [ref] , and the chamber structures could depend on its value.
The Origin of Calabi-Yau Crystals in BPS States Counting · Introduction and Summary · 0.82
Discussion
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